Sanitation and Disease Health Aspects of Excreta and Wastewater Management Richard G. Feachem David J. Bradley Hemda Garelick * D. Duncan Mara FILE COPY r u t- Report No.:11616 Type: (PUB) _ i -.- Title: SANITATION AND DISEASE: HEALTH _ Author: FEACHEM, PICHARD Ext.: 0 Roonl: Dept.: BOOKSTORE 1983 -U ) | i 6 ~ILE COPY V~~~~~~~~~~ X - UL A Wod E. Stu \ W World Bank Studies in Water Supply and Sanitationl 3 Sanitation and Disease WORLD BANK STUDIES IN WATER SUPPLY AND SANITATION 3 Sanitation and Disease Health Aspects of Excreta and Wastewater Management Richard G. Feachem, David J. Bradley, Hemda Garelick and D. Duncan Mara with contributions from J. Coghlan, C. F. Curtis, D. M. E. Curtis W. A. M. Cutting, B. S. Drasar, B. Lloyd W. W. MacDonald, D. M. Mackay, R. L. Muller, J. S. Slade B. A. Southgate, D. C. Warhurst and A. J. Zuckerman Publishedfor the World Bank by John Wiley & Sons Chichester New York Brisbane Toronto Singapore Copyright 'll 1983 by The International Bank for Reconstruction and Development / THE WORLD BANK, 1818 H Street, N.W., Washington, D.C. 20433, U.S.A. No part of this publication may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, electronic, mechanical, photocopying, recording, or other- wise, without the written permission of the World Bank. The views and interpretations in this book are the authors' and should not be attributed to the World Bank, to its affiliated organizations, or to any individual acting on their behalf. Printed and bound in Great Britain at The Pitman Press. Bath Contents Tables and Figures xix 2. Environmental Preface xxiii Classification of Excreta- Scope and Organization related Infections 23 Origins and Related Publications Understanding Exereta- Contributors related Infections 23 Acknowledgments Excreted load 24 Acronyms and Abbreviations xxvii Latency 24 Persistence 25 Multiplication 25 Infective dose 25 PART ONE. THE HEALTH Host response 26 HAZARDS OF EXCRETA: Nonhuman hosts 31 THEORY AND CONTROL Categories of Excreta-related Infections 32 Category I 37 1. Elements and Health Category II 37 Risks of Excreta and Category III 38 Wastewater 3 Category Iv 39 Category v 39 Excreta and Health 3 Category VI 39 Characteristics of Excreta and Summary 39 Sewage 4 Literature Cited 40 Quantities 4 Chemical composition 6 Pathogens in exereta 9 3. The Risks of Excreta to Viruses in excreta 9 Bacteria in excreta 9 Protozoa in excreta 12 Illustrative Sketches 43 Helminths in excreta 12 A Southeast Asian family 43 Magnitude of pathogen A North African family 44 excretion 16 Children and Exereta A note on urinary pathogens 16 Disposal 46 Characteristics of Sullage 16 Distribution of Sanitation Quantities 16 Benefits 47 Composition 18 Health Benefits of Sullage disposal and health 20 Sanitation 48 Literature Cited 20 Methodological issues 48 vi CONTENTS The literature 48 5. Health Aspects of Limitations in Assessing Health Excreta and Night Soil Benefits 49 Best inferences in an optimal case 49 PitLatrines 67 Best inferences in Cleanliness 67 actuality 50 Odor 67 Literature Cited 50 Insect breeding 67 Pathogen survival in the 4. Detection, Survival, and pit 68 Removal of Pathogens in Groundwater pollution 68 Composting Toilets 68 the Environment 53 Technical description 68 Fecal Indicator Bacteria 53 Pathogen survival in Coliform bacteria 54 product 71 Fecal streptococci 54 Cartage Systems 74 Fecal coliform to fecal Night soil deposition 75 streptococci ratio 55 Night soil collection 77 Clostridium perfringens 55 Night soil transport 77 Pseudomonas aeruginosa 55 Night soil treatment 77 Bifidobacterium and other Night soil reuse 77 anaerobic bacteria 56 Composting 78 Fecal concentrations, Pathogen survival 78 detection, and Fly breeding 80 enumeration of bacterial Literature Cited 80 indicators 56 Relation of Fecal Indicator 6. Health Aspects of Bacteria to Excreted Pathogens 56 Sewage Systems 83 Pathogen Indicators 57 A quaprivies and Septic Pathogen indicators for pond Tanks 83 effluents 58 Technical description 83 Pathogen indicators for Pathogen survival 83 effluents from other Conventional Sewage sewage treatment Treatment 86 processes 58 Pretreatment and primary Pathogen indicators for sedimentation 86 noneffluents 58 Trickling filters 87 Survival of Indicators and Activated sludge 88 Pathogens 59 Sludge digestion 88 In feces, night soil, and Sludge dewatering 89 sludge 60 Other sludge treatment In water and sewage 60 processes 89 In soil 61 Complete treatment On crops 61 works 90 Pathogen Survival versus AeratedLagoons 92 Removal in Waste Technical description 92 Treatment 62 Pathogen survival 93 Objectives of Night Soil and Oxidation Ditches 93 Sewage Treatment 62 Technical description 93 Excreta and night soil Pathogen survival 94 treatment 63 Tertiary Treatment 94 Sewage treatment 63 Rapid sand filtration 94 Literature Cited 64 Slow sand filtration 94 CONTENTS vii Land treatment 94 Reuse for Biogas Maturation lagoons 94 Production 107 Other tertiary treatment Technical description 107 processes 95 Pathogen control in reuse of Effluent Chlorination 95 biogas plant slurry 107 Waste Stabilization Discharge of Effluents 109 Ponds 96 Into rivers and lakes 109 Technical description 96 Health issues 109 Pathogen survival 96 Waterborne Literature Cited 96 pathogens 109 Helminths with aquatic 7. Reuse of Excreta and intermediate Discharge of hosts 109 Effluents 99 Into the sea 110 Health issues 110 Reuse in Agriculture 99 Pathogen survival 110 Foodstuffs for human Seafood consumption 99 contamination 110 Health issues 99 Recreational hazards 111 Pathogens reaching the To groundwater 111 field 100 Health issues 111 Pathogen survival 100 Pathogen travel 112 Pathogen Pathogen survival 112 transmission 100 Pathogen control 112 Foodstuffs for animal Nitrates from effluents 112 consumption 101 Health issues 112 Health issues 101 Nitrate control 113 Beef tapeworm Literature Cited 113 infection 101 Salmonellosis 101 8. The Human Element in Tuberculosis 101 SanTation Ssems i1 Other agricultural Sanitation Systems 117 products 102 Relevance of Cultural Values Occupational hazards 102 and Attitudes 118 Pathogen control in Influence of Social Structure agricultural reuse 103 and Organization 119 Reuse in Aquaculture 104 Social and Behavioral Aspects Fish farmning 104 ofLatrine Design 119 Health issues 104 Cost 119 Passive transference of Convenience 119 excreted pathogens 104 Comfort 120 Helminths havingfish as Group or communal intermediate toilets 121 hosts 105 Social and Organizational Helminths with other aquatic Aspects of Exereta intermediate Cartage Systems 121 hosts 105 Social and Organizational Pathogen control 105 Aspects of Exereta Algal culture 105 Reuse Systems 123 Health issues 106 Improving the Management of Pathogen control 106 Urban Sanitation Macrophyte culture 106 Systems 124 Health issues 106 Effectiveness andLimitations Pathogen control 106 of Self-help Schemes 125 'lii CONTENTS Appropriate Health By waste stabilization Education 126 ponds 154 Literature Cited 126 By aerated lagoons 155 By tertiary treatment 155 Lagooning 155 PART TWO. ENVIRONMENTAL Cocigulation 155 BIOLOGY AN1D F 155 EPIDEMIOLOGY OF SPECIFIC DisiyiJection 156 Lanzd treatinent 158 EXCRETED PATHOGENS Otheer processes 16(0 Inactivation by Night Soil and SECTION I. EXCRETED VIRUSES Sludge Treatment Processes 160 9. Enteroviruses, Poliomyelitis, By pit latrines 160 and Similar Viral By anaerobic digestion 160 Infections 133 By drying 161 Description of Pathogens and By heating 162 Diseases 133 By composting 163 Identification 133 By other processes 164 Occurrence 135 Literature Cited 164 Infectious agents 135 Reservoir 135 10. Hepatitis A Virus and Transmission 135 Infectious Hepatitis 173 Incubation period 136 Description of Pathogen and Period of Disease 173 communicability 136 Identification 173 Resistance 137 Occurrence 1 73 Epidemiology 137 Infectious agent 174 Control Measures 137 Reservoirs 174 Individual 137 Transmission 174 Environmental 137 Incubation period 174 Occurrence and Survival in the Period of Environment 138 communicability 174 In surface waters 139 Resistance 174 In ground water 140 Epidemiology 1 74 In drinking water 140 Control Measures 175 In seawater 141 Occurrence and Survival in In feces and night soil 143 the Environment 176 In sewage 144 Inactivation by Sewage In sludge 145 Treatment Processes 177 In soil 146 Inactivation by Night Soil and On crops 147 Sludge Treatment In fish and shellfish 148 Processes 1 77 In the air 150 Literature Cited 178 Inactivation by Sewage Treatment Processes 151 11. Rotavirus and Viral By primary and secondary Gastroenteritis 181 sedimentation 151 By storage 151 Description of Pathogens and By septic tanks 152 Diseases 181 By trickling filters 152 Identification 181 By activated sludge 153 Occurrence 181 By oxidation ditch 154 Infectious agents 181 CONTENTS ix Rotaviruses 182 13. Pathogenic and Adenoviruses 182 Nonpathogenic Astroviruses 182 * * a Calicivirutses 182 Coronavirruses 182 Other Bacterial Enteroviruses 184 Indicators of Fecal Measles viirus 184 Pollution 199 Ani ail ageot and other Description of Pathogen and smiiall r-ouind Disease 199 vliruises 184 Identification 199 Reservoirs 184 Occurrence 199 Transmission 184 Ocrec 9 Incubation period 184 Infectious agents 199 Period fr Enterotoxigenic E. coli Perio mmunicabil y 1 4 (ETEC) 200 communicability 184 Enteroinvasive E. coli Resistance 185 (EIEC) 200 Epidemiology 185 Enteropathogenic E. coli Control Measures 186 (EPEC) 200 Occurrence and Survival in the Reservoirs 201 Environment 187 Transmission 201 Inactivation by Sewage Tration 201 Treatment Processes 188 Icbion p d Inactivation by Night Soil and Period of Sludge Treatment ~~~~~~~~~~~~~~communicability 201 Sludge Treatment Processes 188 Resistance 201 T raue Cie 188 Epidemiology 201 Control Measures 205 SECTION 11. EXCRETED Individual 205 BACTERIA Environmental 205 Fecal Indicator Bacteria 12. Campylobacter and Occurrence and Survival in Campylobacter the Environment 206 Enteritis In surface waters 206 In groundwater 209 Description of Pathogen and In drinking water 210 Disease 193 In seawater 212 Identification 193 In feces and night soil 213 Occurrence 193 In sewage 214 Infectious agent 193 In sludge 215 Reservoirs 195 In soil 215 Transmission 195 On crops 216 Incubation period 196 In fish and shellfish 217 Period of communicability 196 In the air 218 Resistance 196 Inactivation by Sewage Epidemiology 196 Treatment Processes 221 Control Measures 197 By primary and secondary Occurrence and Survival in the sedimentation 221 Environment 197 By storage 222 Inactivation by Sewage By septic tanks 222 Treatment Processes 197 By trickling filters 223 Inactivation by Night Soil and By activated sludge 224 Sludge Treatment By oxidation ditch 224 Processes 197 By waste stabilization Literature Cited 197 ponds 224 x CONTENTS Mechanisms of E. coli 15. Salmonella, Enteric removal in ponds 224 Fevers, and Kinetics of E. coli remnoval SalmonelloseS 251 in ponds 225 By aerated lagoons 226 Description of Pathogens and By tertiary treatment 228 Diseases 251 Lagooning 228 Identification 251 Coagtilation 228 Occurrence 251 Filtration 228 Infectious agents 252 Disinfection 229 Reservoirs 252 Land treatment 230 Transmission 253 Other processes 231 Incubation period 254 Inactivation by Night Soil and Period of Sludge Treatment communicability 255 Processes 231 Resistance 255 By pit latrines 231 Epidemiology 256 By anaerobic digestion 231 Control Measures 259 By heating 232 Individual 259 By composting 232 Carrier surveillance and By limne treatment 233 control 259 By other processes 233 Environmental 260 Literature Cited 233 Occurrence and Survival in the Environment 261 14. Leptospira and In surface water 261 In groundwater 263 Leptospirosis 243 In drinking water 266 Description of Pathogen and In seawater 266 Disease 243 In feces and night soil 267 Identification 243 In sewage 267 Occurrence 243 In sludge and slurry 268 Infectious agent 243 In soil 269 Reservoirs 244 On pasture 270 Transmission 244 On crops 271 Incubation period 244 In fish and shellfish 271 Period of In the air 272 communicability 245 Inactivation by Sewage Resistance 245 Treatment Processes 273 Epidemiology 245 By primary and secondary Control Measures 246 sedimentation 273 Individual 246 By septic tanks 273 Environmental 247 By conventional Occurrence and Survival in the treatment 273 Environment 247 By oxidation ditch 274 In water and sewage 247 By waste stabilization In urine 247 ponds 275 In feces and night soil 248 By tertiary treatment 275 In soil 248 Lagooning 275 Inactivation by Sewage Disinfection 275 Treatment Processes 248 Land treatment 276 Inactivation by Night Soil and Inactivation by Night Soil and Sludge Treatment Sludge Treatment Processes 248 Processes 276 Literature Cited 249 By pit latrines 276 CONTENTS xl Transmission 300 By storagerobicdigesti 276 Incubation period 300 By aerobic digestion 277 Period of By aerobic digestion 277 communicability 300 By drying 277 Resistance 300 By composting 278 Epidemiology 301 By composting 278 ~~Control Measures 301 By coagulation and vacuum Indvul .30 filtration 278 Environmental 302 By lime treatment 278EviomDa 30 By limertreatment 278 Carrier surveillance and By irradiation 278 international regulations 303 16. Shigella and Occurrence and Survival in the Environment 303 SlhigellOSiS 287 In water 303 Description of Pathogen and In feces and night soil 307 Disease 287 In sewage 309 Identification 287 Summary of survival in water Occurrence 287 and wastewater 309 Infectious agent 287 Prolonged survival in water Reservoir 288 and wastewater 313 Transmission 288 A possible aquatic reservoir Incubation period 288 for V. cholerae 315 Period of In sweat 316 communicability 288 On surfaces 316 Resistance 288 In soil 317 Epidemiology 288 On food and crops 317 Control Measures 290 Inactivation by Sewage Individual 290 Treatment Processes 317 Environmental 290 Inactivation by Night Soil and Occurrence and Survival in the Sludge Treatment Environment 291 Processes 322 In water 292 Literature Cited 322 In feces and sewage 292 On surfaces 292 18. Yersinia and In food 293 Yersiniosis 327 On crops 293 In thc air 293 Description of Pathogen and Inactiviation by Sewage Disease 327 I,activiation by Sewage Identification 327 Treatment Processes 293 Occurrence 327 Inactivation by Night Soil and Infectious agent 327 Sludge Treatment Reservoirs 328 Processes 293 Transmission 328 Literature Cited 294 Incubation period 328 17. Vibrio cholerae and Period of communicability 328 Cholera 297 Resistance 328 Description of Pathogens and Epidemiology 328 Disease 297 Control Measures 329 Identification 297 Occurrence and Survival in the Occurrence 298 Environment 329 Infectious agents 299 Inactivation by Sewage Reservoir 300 Treatment Processes 330 xii CONTENTS Inactivation by Night Soil and Environmental 340 Sludge Treatment Occurrence and Survival in the Processes 330 Environment 342 Literature Cited 330 In water and water supplies 342 SECTION III. EXCRETED In seawater 342 PROTOZOA In feces and night soil 342 19. Balantidium and In sewage 342 On surfaces 342 BalantidiasiS 333 In soil 342 Description of Pathogen and On crops 342 Disease 333 Summary 343 Identification 333 Inactivation by Sewage Occurrence 333 Treatment Processes 343 Infectious agents 333 By sedimentation 343 Reservoirs 334 By trickling filter 344 Transmission 334 By activated sludge 344 Prepatent and incubation By oxidation ditch 344 periods 334 By waste stabilization Period of ponds 344 communicability 334 By aerated lagoons 344 Resistance 334 By tertiary treatment 344 Epidemiology 335 IH'u.'. 344 Control Measures 335 Disintftction 344 Individual 335 Land treatmnent 344 Environmental 335 Inactivation by Night Soil and Occurrence and Survival in the Sludge Treatment Environment 335 Processes 344 Inactivation by Sewage Literature Cited 345 Treatment Processes 336 Inactivation by Night Soil and 21. Giardia and Sludge Treatment Giardiasis 349 Processes 336 Description of Pathogen and Literature Cited 336 Disease 349 20. Entamoeba histolytica Identification 349 Occurrence 349 and Amebiasis 337 Infectious agent 349 Description of Pathogen and Reservoirs 350 Disease 337 Transmission 350 Identification 337 Prepatent and incubation Occurrence 337 periods 351 Infectious agent 337 Period of Reservoirs 338 communicability 351 Transmission 338 Resistance 351 Prepatent and incubation Epidemiology 351 periods 338 Control Measures 352 Period of Individual 352 communicability 338 Environmental 352 Resistance 339 Occurrence and Survival in the Epidemiology 339 Environment 352 Control Measures 340 In water and water Individual 340 supplies 353 CONTENTS Xiii In feces and night soil 353 By drying 370 In sewage 353 By heating 370 Summary 353 By composting 370 Inactivation by Sewage Literature Cited 371 Treatment Processes 354 Inactivation by Night Soil and 23. Ascaris and Sludge Treatment Processes 354 Ascariasis 375 Literature Cited 354 Description of Pathogen and Disease 375 SECTION IV. EXCRETED Identification 375 HELMINTHS Occurrence 375 22. Ancylostoma, Necator, Infectious agent 375 Reservoir 376 and Ancylostomiasis 359 Transmission 376 Description of Pathogen and Prepatent and incubation Disease 359 periods 377 Identification 359 Period of Occurrence 359 communicability 377 Infectious agents 361 Resistance 377 Reservoir 361 Epidemiology 377 Transmission 361 Control Measures 380 Prepatent and incubation Individual 380 periods 362 Environmental 380 Period of Occurrence and Survival in the communicability 362 Environment 384 Resistance 362 In surface water 384 Epidemiology 362 In groundwater 385 Control Measures 364 In drinking water 385 Individual 364 In seawater 385 Environmental 365 In feces and night soil 385 Occurrence and Survival in the In sewage 385 Environment 366 In sludge 385 In water 366 In soil 386 In feces and night soil 367 On crops 386 In sewage 367 Inactivation by Sewage In sludge 367 Treatment Processes 387 In soil 367 By septic tanks 387 On crops 367 By conventional Inactivation by Sewage treatment 388 Treatment Processes 368 By waste stabilization By septic tanks 368 ponds 388 By conventional By tertiary treatment 389 treatment 368 Inactivation by Night Soil and By waste stabilization Sludge Treatment ponds 368 Processes 389 By tertiary treatment 369 By pit latrines 389 Inactivation by Night Soil and By biogas plants 389 Sludge Treatment By digestion 390 Processes 369 By storage 390 By digestion 369 By drying 391 By ovicides and By heating 391 larvicides 369 By composting 392 xiv CONTENTS By other processes 392 Inactivation by Night Soil and ., ~~~~~~~~Sludge Treatment Chemical ovicides 392 Plocesseat410 Irradiation 392 Literature Cited 410 Literature Cited 393 24. Clonorc his and 26. Enterobius and Enterobiasis 413 Clonorchiasis 401 Description of Pathogen and Description of Pathogen and Disease 413 Disease 401 Identification 413 Identification 401 Occurrence 413 Occurrence 401 Infectious agent 413 Infectious agents 401 Reservoir 413 Reservoirs 401 Transmission 413 Transmission 401 Prepatent and incubation Prepatent and incubation periods 413 periods 402 Period of Period of communicability 414 communicability 402 Resistance 414 Resistance 403 Epidemiology 414 Epidemiology 403 Control Measures 415 Control Measures 404 Occurrence and Survival in the Occurrence and Survival in the Environment 415 Environment 404 Inactivation by Sewage Inactivaction by Sewage Treatment Processes 415 Treatment Processes 404 Inactivation by Night Soil and Inactivation by Night Soil and Sludge Treatment Sludge Treatment Processes 416 Processes 404 Literature Cited 416 Literature Cited 404 27. Fasciola and 25. Diphyllobothrium and Fascioliasis 417 Diphyllobothriasis 407 Description of Pathogen and Description of Pathogen and Disease 417 Disease 407 Identification 417 Identification 407 Occurrence 417 Occurrence 407 Infectious agent 417 Infectious agent 407 Reservoirs 417 Reservoir 407 Transmission 417 Transmission 407 Prepatent and incubation Prepatent and incubation periods 418 periods 409 Epidemiology 418 Period of Control Measures 418 communicability 409 Occurrence and Survival in the Resistance 409 Environment 418 Epidemiology 409 Inactivation by Sewage Control Measures 409 Treatment Processes 419 Occurrence and Survival in the Inactivation by Night Soil and Environment 409 Sludge Treatment Inactivation by Sewage Processes 419 Treatment Processes 410 Literature Cited 419 CONTENTS xv 28. Fasciolopsis and 30. Minor Intestinal Flukes Fasciolopsiasis 421 and Infections They Description of Pathogen and Cause 431 Disease 421 Identification 421 Description of Pathogens and Occurrence 421 Diseases 431 Ifctusente 421 Identification 431 Infectsous agent421 Occurrence 431 Transmission 421 Infectious agents 431 Transmission 421 Reservoirs 431 Prepatent and incubation Transmission 431 periods 421 Period of Prepatent and incubation communicability 422 periods 434 Resistance 422 Period of Epidemiology 422 communicability 434 Control Measures 423 Resistanc 434 Occurrence and Survival in the Epidemology 434 Control Measures 435 Environment 423 Occurrence and Survival in the Inactivation by Sewage Environment 435 Treatment Processes 424 Inactivation by Night Soil and Inactivation by Sewage ,. ~~~~~~~~~Treatment Processes 435 Sludge Treatment Inactivation by Night Soil and Processes 424 Literature Cited 424 Sludge Treatment Processes 435 Literature Cited 435 29. Hymenolepis and 31. Paragonimus and Hymenolepiasis 425 Paragonimiasis 437 Description of Pathogen and Description of Pathogen and Disease 425 Disease 437 Identification 425 Identification 437 Occurrence 425 Occurrence 437 Infectious agent 425 Infectious agent 437 Reservoirs 425 Reservoir 437 Transmission 425 Transmission 437 Prepatent and incubation Prepatent and incubation periods 427 periods 439 Period of Period of communicability 427 communicability 439 Resistance 427 Resistance 439 Epidemiology 427 Epidemiology 439 Control iVMeasures 427 Control Measures 439 Occurrence and Survival in the Occurrence and Survival in the Environment 427 Environment 440 Inactivation by Sewage Inactivation by Sewage Treatment Processes 427 Treatment Processes 440 Inactivation by Night Soil and Inactivation by Night Soil and Sludge Treatment Sludge Treatment Processes 428 Processes 440 Literature Cited 428 Literature Cited 440 xci CONTENTS 32. Schistosoma and Inactivation by Night Soil and Schistosomiasis 443 Sludge Treatment Description of Pathogen and Pirocesses 460 Disease 443 ~~~~~Literature Cited 460 Disease 443 Identification 443 34. Taenia, Taeniasis, and Occurrence 444 Infectious agents 444 Cysticercosis 463 Reservoirs 444 Description of Pathogen and Transmission 444 Disease 463 Prepatent and incubation Identification 463 periods 447 Occurrence 463 Period of Infectious agent 463 communicability 447 Reservoirs 465 Resistance 447 Transmission 465 Epidemiology 447 Prepatent and incubation Control Measures 449 periods 465 Individual 449 Period of Environmental 449 coniinunicability 465 Occurrence and Survival in the Resistance 465 Environment 451 Epidemiology 467 In water 451 Control Measures 468 In feces and night soil 451 Individual 468 In urine 451 Environmental 468 In sewage 451 Occurrence and Survival in the Inactivation by Sewage Environment 468 Treatment Processes 452 In water 468 Inactivation by Night Soil and In sewage 468 Sludge Treatment In sludge 469 Processes 452 On pasture 469 Literature Cited 453 Inactivation bJ' Sewage Treatment Processes 469 33. Strongyloides and Inactivation by Night Soil and Strongyloidiasis 457 Sludge Treatment Processes 470 Description of Pathogen and L itrueCied 470 Disease 45 7 ~~~~~Literature Cited 470 Disease 457 Identification 457 35. Trichuris and Occurrence 457 Infectious agent 457 Trichuriasis 473 Reservoirs 457 Description of Pathogen and Transmission 457 Disease 473 Prepatent and incubation Identification 473 periods 458 Occurrence 473 Period of Infectious agent 473 communicability 458 Reservoir 473 Resistance 459 Transmission 473 Epidemiology 459 Prepatent and incubation Control Measures 459 periods 474 Occurrence and Survival in the Period of Environment 460 communicability 474 Inactivation by Sewage Resistance 474 Treatment Processes 460 Epidemiology 474 CONTENTS x)ii Control Measures 475 The Association of Culex Individual 475 pipiens with Polluted Environmental 475 Water 485 Occurrence and Survival in the Culex pipiens Breeding in Environment 476 Waste Stabilization In water 476 Ponds 487 In feces and night soil 476 Methods for Culex pipiens In sewage 476 Control 488 In sludge 476 Case studies in control 488 In soil 476 Control by modifying the On crops 476 physical Inactivation by Sewage environment 489 Treatment Processes 477 Control by insecticides and Inactivation by Night Soil and oils 490 Sludge Treatment Conclusions 492 Processes 477 Literature Cited 492 Literature Cited 478 37. Flies, Cockroaches, and Excreta 495 SECTION v. INSECTS AND Flies Associated with Waste EXCRETA Disposal 495 Cockroaches 496 36. Culex pipiens Flies, Cockroaches, and Mosquitoes and the Health 496 Transmission of Transmission of Excreted Bancroftian Pathogens 497 Methods of Fly and Cockroach Filariasis 483 Control 498 The Biology of Culex pipiens Modifying the physical Mosquitoes 483 environment 498 Bancroftian Filariasis 483 Insecticides and other Culex pipiens as a Vector and chemicals 499 as a Nuisance 484 Literature Cited 499 Tables and Figures Tables 3-2. Ranking of excreta disposal technologies by 1-1. Fecal weights around the world 5 ease of operation and maintenance, water 1-2. Composition of human feces and urine 6 needs, and health benefits 51 1-3. Possible standard biochemical oxygen 4-1. Number of indicator bacteria commonly demand (BoD5) content of exereta and night found in human feces 56 soil 7 4-2. Survival times of excreted pathogens in feces, 1-4. BOD5 contributions per capita in urban night soil, and sludge at 20-30°C 60 sewage 8 4-3. Survival times of excreted pathogens in fresh 1-5. Viral pathogens excreted in feces 9 water and sewage at 20-30°C 60 1-6. Bacterial microflora of human feces by 4-4. Factors affecting survival time of enteric national diet 11 bacteria in soil 61 1-7. Bacterial pathogens excreted in feces 12 4-5. Survival times of excreted pathogens in soil 1-8. Protozoal pathogens excreted in feces 13 at 20-30°C 61 1-9. Helminthic pathogens excreted in feces 14 4-6. Survival times of excreted pathogens on 1-10. Possible output of selected pathogens in the crops at 20-30°C 62 feces and sewage of a tropical community of 5-1. Probable pathogen content in final product 50,000 in a developing country 17 of anaerobic composting toilets operating at 1-11. Allocation of water use in sewerless rural ambient temperatures in warm households in developing countries 18 climates 74 1-12. Pollution loads of wastewater sampled from 6-1. Theoretical settling velocities of protozoal various plumbing fixtures in the USA 19 cysts and helminth eggs 87 1-13. Bacterial content of sullage in the USA 19 9-1. Human excreted viruses 134 2-1. Summary of selected literature on the effect 12-1. Prevalence of excretion of Campylobacter on health of improved excreta disposal 26 and other enteric pathogens by individuals 2-2. Environmental classification of excreted with and without diarrhea in twelve infections 33 countries 194 2-3. Basic epidemiological features of excreted 13-1. Etiology of diarrhea reported to Matlab pathogens by environmental category 34 Hospital, Bangladesh, during 1977 202 2-4. Category I and ii pathogens (from table 2-2) 13-2. Some reported concentrations of fecal ranked by median infective dose (ID50) 36 bacteria in untreated domestic water sources 2-5. Category I and ii pathogens (from table 2-2) in developing countries 208 ranked by persistence outside host 36 13-3. Fecal bacteria removal rate constants in 2-6. ID50 and persistence of category I and II series of waste stabilization ponds 227 pathogens (from table 2-2) commonly and 15-1. Variations in the nomenclature of some rarely transmitted in affluent European important types of Salmonella 252 communities 36 15-2. Period and point prevalences of Salmnonella 3-1. Maximum prevalence of excreted pathogens and Shigella excretion by black school- (from table 2-2) by age in indigenous children in the Transvaal, Republic of South populations of endemic areas 46 Africa 264 xix xx TABLES AND FIGURES 15-3. Salmonella removal at the Woking trickling 2-2. Factors affecting the transmission of an filter plant, UK 274 infective dose 24 15-4. Saimoniella removal at the Guildford 2-3. Involvement of other vertebrates in activated sludge plant, UK 274 transmission of human excreted 17-1. Survival of Vibrio cholerae in surface infections 32 waters 304 2-4. Persistence outside the host of excreted 17-2. Survival of V cholerae in well water 306 pathogens (categories I-v from table 2-2) 17-3. Survival of V cholerae in tap water 308 over time 37 17-4. Survival of V chlolerae in mineral 2-5. Length and dispersion of transmission cycles water 309 of excreted infections (categories i-V from 17-5. Survival of 1' cholerae in seawater 310 table 2-2) 38 17-6. Survival of V cholerae in feces 311 5-1. Conventional unimproved pit latrine 68 17-7. Survival of V cholerae in sewage 312 5-2. Ventilated improved pit (VIP) latrine 69 17-8. rg9 values in hours for various types of V 5-3. Reed Odorless Earth Closet (ROEC) 70 chlolerae in various waters and 5-4. "Multrum" continuous-composting wastewaters 314 toilet 71 17-9. Survival of V chlolerace on surfaces 316 5-5. Double-vault composting (DVC) 17-10. Survival of V cholerae on food and toilets 72 crops 318 5-6. Pathogen flow through a batch composting 20-1. Some studies on the relationships between toilet (double-vault) 74 Entamioeba histolvtica infection and 5-7. Bucket latrine and cartage 75 environmental sanitation 341 5-8. Alternative designs for vault toilets 76 22-1. Prevalence of hookworm infection in fifteen 5-9. Influence of time and temperature on countries 363 selected pathogens in night soil and 22-2. Some studies on the effect of mass sludge 79 chemotherapy on hookworm 5-10. Pathogen flow through a well-managed infection 365 thermophilic composting process 80 22-3. Some studies on environmental influences on 6-1. Septic tank designs 84 hookworm infection 366 6-2. Conventional aquaprivy 85 2'-4. Reduction of helminth eggs by sewage 6-3. Pathogen flow through a septic tank 86 treatment processes in India 369 6-4. Components of conventional sewage 92-5. Tolerance of hookworm eggs and larvae to treatment 87 high and low temperatures 371 6-5. Pathogen flow through various continuous 23-1. Some studies on the reduction and sludge treatment processes 89 subsequent rise of ascariasis prevalence 6-6. Pathogen flow through various batch sludge following mass chemotherapy 381 treatment processes 90 23-2. Some studies on environmental influences on 6-7. Pathogen flow through a conventional ascariasis 383 sewage treatment plant featuring trickling 23-3. Some studies on Ascaris eggs in composting filters 91 processes 392 6-8. Pathogen flow through a conventional 23-4. Some literature on Ascar-is ovicides 393 sewage treatment plant featuring activated 29-1. Duration of infectivity of Hy inmenolepis nana sludge 91 eggs stored under various conditions 42N 6-9. Flow diagram for an aerated lagoon 34-1. Some studies on the survival of Taeniia eggs incorporating sludge digestion 92 in grass, silage. and soil 469 6-10. Stages in development of a waste 35-1. Some studies on environmental influences on stabilization pond-aerated lagoon trichuriasis 476 system 93 37-1. Insect fauna of "dry" latrines 497 6-11. Flow diagram for an oxidation ditch 93 6-12. Pathogen flow through a waste stabilization Figures pond system 97 7-1 Tvpical biogas digesters 108 2-1. The links between excreta and 9-1. Polio-, adeno- and reoviruses under infection 23 electronmicroscopy 136 TABLES AND FIGURES xxi 9-2. The influence of time and temperature on 27-1. An adult Fasciola hepatica under a light enteroviruses 163 microscope 418 10-1. Hepatitis A viruses under transmission 28-1. Known geographical distribution of electronmicroscopy 174 Fasciolopsis buski 422 11-1. Agents of viral gastroenteritis 183 28-2. An adult Fasciolopsis buski under a light 12-1. Campylobacter under scanning microscope 423 electronmicroscopy 195 29-1. Head (scolex) and neck of Hymenolepis nana 13-1. Escherichia coli and Streptococcus under under scanning electronmicroscopy 426 scanning electronmicroscopy 200 30-1. Known geographical distributions of 14-1. Leptospira under scanning Heterophyes heterophyes and Metagonimnus electronmicroscopy 244 yokogawai 432 15-1. Salmonella enteritidis under scanning 30-2. Known geographical distribution of electronmicroscopy 252 Gastrodiscoides hominis 432 15-2. The influence of time and temperature on 30-3. Adult Heterophyes heteroplhyes (a) and salmonellae 277 Metagonimus yokogawai (b) under a light 16-1. The influence of time and temperature on microscope 433 Shigella 294 30-4. An adult Gastrodiscoides hominis under a 17-1. The global spread of cholera. 1961-75 298 light microscope 434 17-2. Vibrio cholerae under scanning 31-1. Known geographical distribution of electronmicroscopy 299 Paragonimus 438 17-3. The influence of time and temperature on 1 31-2. An adult Paragonimuis westermani under a cholerae 322 light microscope 438 19-1. Drawing of a trophozoite of Balantidium 32-1. Known geographical distribution of coli 334 Schistosoma haematobium and S. 20-1. A trophozoite of Entamoeba histolytica japonicum 445 under scanning electronmicroscopy 338 32-2. Known geographical distribution of S. 20-2. The influence of time and temperature on mansoni 445 Ent. histolytica cysts 343 32-3. A male and female S. mansoni under 21-1. Trophozoites of Giardia lamblia under scanning electronmicroscopy 446 scanning electronmicroscopy 350 32-4. The influence of time and temperature on 22-1. Known geographical distribution of Schiistosoma eggs 453 Ancylostoma duodenale 360 33-1. An adult Strongyloides stercoralis under a 22-2. Known geographical distribution of Necator light microscope 458 anlericanius 360 34-1. Known geographical distribution of Taenia 22-3. The head (scolex) of an Ancvlostomna under a saginata 464 light microscope 361 34-2. Known geographical distribution of T 22-4. The influence of time and temperature on soliumn 464 hookworm eggs and larvae 370 34-3. T solium and T. saginata 466 23-1. Ascaris in situ 376 34-4. The influence of time and temperature on 23-2. The influence of time and temperature on Taenia eggs 470 Ascaris eggs 391 35-1. A male (left) and female (right) Trichwl7is 24-1. Known geographical distribution of t7ic/ziu7a under a light microscope 474 Clonorchis sinensis 402 36-1. Known geographical distribution of Culex 24-2. An adult of OpisthorchisJelinetis under a pipiens mosquitoes and Bancroftian light microscope 403 filariasis 484 25-1. Known geographical distribution of 36-2. Larval and adult Culex pipiens Diphyllobothrium latum 408 mosquitoes 485 25-2. A length of D. latunm expelled after 36-3. Insect traps for pit latrines 491 treatment 408 37-1. The common housefly, Musca 26-1. Adult pinworms, Enrteobius comnestic a 496 ve1 nriclularis 414 Preface MANY IMPORTANT infectious diseases are associated disposal systems. To achieve this gain as much with human excreta. The most common association is information as possible is needed about the interactions that the pathogens causing the disease leave an infected between excreta and health-information not only person by way of the feces orurine. Excreta are thus the about broad epidemiological issues of disease pre- direct source of these infections. Less commonly and vention through improved excreta disposal, but also directly, excreta may be associated with the breeding of about the effect of particular excreta disposal and reuse insects that are vectors of disease. The hygienic technologies on the survival and dissemination of management and disposal of human excreta is thus of particular pathogens. central importance in the control of these associated diseases. This is true in both poor and rich countries and across all climatic zones. Most people in the developing countries do not have adequate disposal systems for human wastes. A survey Scope and Organization of developing countries by the World Health Organization (WHO) in 1975 indicated that 75 percent This book sets out to provide such information for a of urban dwellers did not have sewerage (that is, sewers broad readership. It is intended for the wide spectrum for disposal of excreta) and that 25 percent had no of professionals concerned with sanitation and public disposal system of any kind. In rural areas, 85 percent health: those who control -such as health planners, lacked any adequate excreta disposal facility. Major economists, and public health administrators; those national and international initiatives are clearly who implement-such as environmental hygienists, required if any substantial improvement in sanitation sanitary engineers, public health workers, and health systems in the developing world is to be made in the educators; and those who study and advise- next few decades. especially epidemiologists, microbiologists, and para- In the more wealthy and industrialized countries, sitologists. The book has been written with a minimum most people have adequate excreta disposal arrange- of technical jargon so that it can be readily absorbed by ments in their homes and places of work. The people from different professional backgrounds; treatment and disposal of human wastes, however, technical terms are defined when they are used, and pose enormous problems for the responsible agencies. acronyms and abbreviations are listed on page 22. Large cities produce such volumes of sewage and such The book has two parts. Part One, entitled "The quantities of sludge that the infrastructure for the safe Health Hazards of Excreta: Theory and Control," disposal of these wastes may be stretched to the limit. It presents a distillation of available knowledge about is in this context that decisions about pathogen excreta, night soil, and sewage and their effects on destruction in sewage and sludge and about the risks to health. The emphasis is on presenting the complex, public health of various treatment and disposal and sometimes contradictory, evidence as clearly and options become of the utmost importance. concisely as possible. The source for Part One is In all countries, public health is of central largely, but not entirely, the literature. On occasion, we importance in the design and implementation of have gone beyond the literature to state what we excreta disposal projects, and better health is the main anticipate to be the case; this theoretical content is social and economic benefit that planners and based on a fundamental understanding of the economists hope to gain by investing in excreta particular disease or pathogen. Inevitably, the need for xxiii xxitv PREFACE clarity and the demands of limited space have Appropriate Sanitation Alternlatives: A Planninzg and necessitated some oversimplification. Design Manual (by J. M. Kalbermatten, D. S. Julius, C. Part Two, entitled "Environmental Biology and G. Gunnerson, and D. D. Mara). In addition, the Epidemiology of Specific Excreted Pathogens," con- Transportation and Water Department of the World tains twenty eight chapters, each describing the Bank issues a series of reports under the main environmental properties of a specific excreted title Appropriate T1 .1m. ; jor Water Supply and pathogen or group of excreted pathogens and the Sanitation-available from the Bank's Publication epidemiology and control of the infections these Unit (for information on obtaining these and related pathogens cause. Emphasis is placed on the occurrence World Bank publications, see the last page of this and survival of the pathogen in the environment and on book). Twelve reports have been published in this the efficacy of various waste treatment processes in series so far. reducing or eliminating the pathogen. For ease of reference. the chapters of Part Two are grouped by biological class of pathogen in five sections-the excreted viruses, bacteria, protozoa, and helminths, Contributors and the excreta-related insect vectors of disease. As in Part One, the material in Part Two is derived from the The book has been pepared by the Ross Institute of literature. Where documentation is ambiguous or Tropical Hygiene from the work of a group of contradictory, we have attempted to give a conser- bacteriologists, engineers, entomologists, epidemio- vative opinion-overestimating, for example, the logists, parasitologists, and virologists from the ability of a pathogen to survive hostile environmental London School of Hygiene and Tropical Medicine and conditions. elsewhere. Contributing specialists, their affiliations, Each chapter in Parts One and Two has its own list and the chapters to which they contributed are: of literature cited. The several hundred papers and publications cited were selected from among a total ('i collection of several thousand items assembled during Dr. J. Coghlan 14 the writing of this book. The literature searches for the Lepto-spirosis Reference Laboratory, London various chapters were ended between late 1980 and mid- 1981. The literature throughout has been selected from Ross C. .titute of Trop3cai H6oienc, London Shool 3 international sources (a considerable number of Czech. of H,giene and Tropcal Medicine French, German. Japanese. Korean, Russian, Spanish. and other non-English language publications have been Dr. D. M. E. Curtis 8 used). i ustit ite of Local Gov erenent Studtes. tUnirersit!y of Despite its division into two parts, the book is meant Bir;ninghaoi to be used as a unit. Readers desiring elaboration or Dr. W. A. M. Cutting I support of statements made in Part One must refer to Department of Child Lije and Health, Uini.er.itt of Part Two. Edinburgh IjormerlyH of Ross Institute. Lon'don Schzool of Hygiene and Tropical Medicinel Dr. B. S. Drasar 12. 13. 16 Origins and Related Publications Deparnment of V'edical Microbiology, Lonidon Scthool of Higiene and 7ropical Medicine This book arises out of a World Bank research Dr. B. Llovd ]5. 17. 18 project in appropriate technology for waste disposal D o . t 3 ~~~~~~~~~~~~~~~~Department of Mvticobiology, Uniersitr of Sarrse; that was initiated in 1976 by the Bank's chief water and wastes adviser. Mr. John M. Kalbermatten. The results Professor W. W'. Macdonald 36 of this research are published in three books, under the Department oj Entomology. Lirerpool Schlool of series title "World Bank Studies in Water Supply and Tropicail Medicine (fortmerlh Department of Sanitation." Numbers 1 and 2 of this series were Entomology, London School of Hygiene andel published in 1982 by the Johns Hopkins University Tropical Medicinee) Press and are entitled Appropriate Sanitation Alternac- Dr. D. M. Mackas 17 tives: A Technical and Econonfic .4ppraisal (by J. M. Ross Inistitute of 7ropical HYgiene. London School Kalbermatten. D. S. Julius, and C. G. Gunnerson) and of Hygiene and Tropical .Mledicine PREFACE xx U Dr. R. L. Muller 24, 25. 26, 27, Department of The World Bank was instrumental in Commonwealthl Institute o( Helminthology, St. 28, 29. 30. 31. guiding this book from its first manuscript in 1978 to its .41bans (former/v Department oj Medical 33 34 final manuscript in 1981, and so to the printed book in Helminthology, London School of HJygiene aind 1983. We are especially indebted to Mr. James McEuen Tr-opical Medlicinie) for his major contribution to the structure and content Dr. J. S. Slade 9 of the book. Jamie Cameron, Ian McIntosh, Lyn Udall Thames Water Authority, London and their colleagues at John Wiley & Sons, UK, ensured the rapid and efficient publication of the final Dr. B. A. Southgate 22 manuscript. Ross Institute of Tropical Hygiene, London School We thank the reviewers of earlier manuscripts for of Hygiene anid Tropical Medicine their thoughtful and constructive suggestions: Dr. F. Dr. D. C. Warhurst 19. 20. 21 A. Butrico, Dr. V. J. Cabelli, Dr. W. Crewe, Dr. B. Departnment of Medical Protoz00logy, Londmi Cvjetanovic, Dr. R. H. Gilman, Dr. J. M. Hughes, Dr. B. School of Hvgiene anld Tropical Medicine R. Laurence, Dr. J. C. Leighty, Mr. W. L. Reyes, Dr. H. 1. Shuval, Dr. B. B. Sundaresan, Professor A. Wolman, Professor A. J. Zuckerman 10 and Professor A. M. Wright. Departmnent of Medical Microbiology, London Many others have assisted in various ways, and we Schiool of Hygienie and Tr-opical Medicine especially acknowledge Dr. F. 1. C. Apted, Ms. Angela * Sadly, Dr. Donald Mackay died while this book was going to Batten, Ms. Pauline Berrington, Dr. M. Blaser, Ms. press. He made a substantial contribution to it, and we trust that he Elizabeth Burge, Ms. Margaret Carroll, Mr. P. would have been pleased by the final result. Hawkins, Professor K. Ives, Dr. B. Karlin, Ms. Jane Lillywhite, Dr. M. McGarry, Dr. G. Groenen, Mr. C. The book evolved, the group of contributors was Milr an'r .B.Sirw convened, and the chapters on specific diseases initially Dr. a.d DuggMn an Ms.S each comprised a short general account followed by W c Museum of Mec Sciec London we abstracted references. Following the review ofthis draft, Wellcome Museum of Medcal Science, London, were Dr. Feachem rewrote these chapters, incorporating of great assistance in collecting the photographi ad. Feachem r o thters,lninuscrorat.i illustrations for Part Two. A considerable number of aTinchalptersai toeirf form a econtin account. the references cited were translated from the originals. Thb hpesi their fiagfrawrah and we acknowledge the valuable work of Sandy Cairncross (Portuguese), Mario Campa (Italian), Agnes Candler (French), Zuzana Feachem (Czech, Acknowledgments Slovak, and Russian), and Rieko Fukano (Japanese). Bibliographic, editorial, and secretarial assistance was This review of sanitation and disease was originally ably provided by Mary-Grace Browning, Agnes commissioned by The World Bank, and the Bank Candler, Jackie Channon, Margaret Dawson, Alison comm1ssloned ~ ~ ~ ~ ~ ~ aves Lynn Daves Dianne Fishman and Jilln '. ' covered a proportion of the costs involved in the Davies, Lynne Davies, Dianne Fishman. and preparation of the manuscript. We are indebted to the ha Bank's staff for their support and encouragement. We RICHARD G. FEACHEM particularly acknowledge the assistance of Mr. John DAVID J. BRADLEY Kalbermatten, Mr. Charles Gunnerson, Dr. DeAnne London HEMDA GARELICK Julius, and Mr. Richard Middleton. The Publications June 1982 D. DUNCAN MARA Acronyms and Abbreviations BOD Biochemical oxygen demand BOD, Biochemical oxygen demand by the standard test (5 days at 20°C) °C Degrees Celsius DNA Deoxyribonucleic acid DVC Double-vault composting [toilet] EIEC Enteroinvasive Escherichia coli ELISA Enzyme-linked immunosorbent assay ENT E. coli enterotoxin plasmids EPEC Enteropathogenic E. coli ETEC Enterotoxigenic E. coli ID50 Median infective dose IEM Immuno-electronmicroscopy LT Heat-labile [E. coli enterotoxin] PFU Plaque-forming unit PVc Polyvinyl chloride RNA Ribonucleic acid ROEC Reed Odorless Earth Closet ST Heat-stable [E. coli enterotoxin] t9o Time at which 90 percent re- duction [in number of excreted pathogens] is achieved TAB Salmonella typhi and S. paratyphi A and B [vaccine] TCID,, Median tissue culture infective dose VIP Ventilated improved pit [latrine] WHO World Health Organization xxvii Part One The Health Hazards of Excreta: Theory and Control 1 Elements and Health Risks of Excreta and Wastewater IN THIS OPENING CHAPTER the nature and health risks children and infants in developing countries. Cholera, of excreta, sewage and sullage are examined. Attention whether endemic or epidemic in form, is accompanied is given to both the composition and likely pathogen by numerous deaths in all age groups-although content of human wastes, the quantities of excreta and under endemic conditions, it is children who suffer the sullage produced in different countries of the world, most fatalities. Other diseases, such as hookworm and the hazards posed to public health by the infection and schistosomiasis, cause chronic debilitat- microbes, parasites, and insects implicated in the ing conditions that impair the quality of life (however spread of excreta-related human infections. defined) and make the individuals more liable to die from superimposed acute infections. These diseases, and the many others discussed in this Excreta and Health book, start their journey from an infected individual to a new victim when the causative agent is passed in the This book is about human excreta and disease. excreta. Therefore the collection, transport, treatment, Excreta are defined here as human feces and urine. and disposal of human excreta are of the utmost Many infections, in excess of fifty even if the different importance in the protection of the health of any numbered types of viruses and serotypes of enteric community. They become even more important in bacteria are ignored, are transmitted from the excreta those societies which recognize the value of human of an infected person to the mouth of another. The excreta in agriculture, aquaculture or gas production disease-causing agents (the pathogens) of these and therefore reuse, rather than dispose of, their raw or infections travel from anus (or, rarely, bladder) to treated wastes. Such reuse systems have a positive role mouth by a variety of routes-sometimes directly on in supporting economic activity and food production contaminated fingers and sometimes on food, utensils, and are often cheaper than alternative methods of in water, or by any other route which allows minute disposal. However, reuse systems present a challenge to amounts of infected excreta to be ingested. Some of the public health engineer to design and develop these pathogens may reinfect, not only through the technologies that will not pose unacceptable risks to mouth, but by inhalation of dust or aerosol droplets. health. There are also a few infections (notably hookworms Around the world, and in most countries, there are and schistosomiasis) that can penetrate through the millions of people who lack any hygienic and skin. acceptable method of excreta disposal. There are also Human excreta are the principal vehicle for the governments and international agencies spending, or transmission and spread of a wide range of preparing to spend, large sums of money to improve communicable diseases. Some of these diseases rank this situation. If these governments and agencies could among the chief causes of sickness and death in arrange, by massive investment and miraculous social societies where poverty and malnutrition are ubiqui- and economic transformation, that everyone be tous. Diarrheas, for instance, are-together with provided with a modern house with water and malnutrition, respiratory disease and endemic sewerage connections, the health dimensions discussed malaria-the main causes of death among small in this book would be less relevant. But change will not 3 4 HEALTH HAZARDS OF EXCRETA come in this way. Change will come slowly and fecal weights than others. The data in table 1-1 show unevenly, and resources of money, manpower, and wet fecal weights reported by various authors from institutions will often be very scarce. The recipients of several countries. new excreta disposal technologies may be unable to The water content of feces varies with fecal weight. In pay completely for them, or they may lack the a community with an average wet fecal weight of necessary experience and education to use them 100-1 50 grams per day, for instance, the water content effectively. Always there will be many constraints, and will be around 75 percent. As fecal weight increases, so with these constraints will come difficult choices. does the proportion of water: at a fecal weight of 500 Choices need to be made about all aspects of excreta grams per day, the water content of the stool may be disposal. There will be choices about technology, about 90 percent. The frequency of defecation also about ultimate disposal, about reuse, about sullage, varies with fecal weight. In Europe and North America, about payment, about management, and about all the where fecal weights are generally under 200 grams per other elements that make up a sanitation system. day, the average frequency is one stool daily. In rural A number of factors will influence these choices, areas of developing countries, especially where diet is but one central factor is heealth. Since a primary vegetarian and fecal weights are high, a daily frequency motivation for investing in excreta disposal is of two or three stools is common. improved health, decisionmakers will need to under- Most adults produce between 1.0 and 1.3 kilograms stand the health implications of the various choices. of urine per day, but this depends on how much they The more limited are the resources, the more difficult drink and sweat, and this-as with fecal output-in the choices and decisions become-and the more it is turn depends on diet, occupation, climate, and other necessary to understand precisely and in detail the factors. If possible, local data should be consulted in relationships between excreta and health. designing a night soil system. In the absence of such data, a working assumption in a developing country is that adults will produce daily about 350 grams of feces Characteristics of Excreta and Sewage and 1.2 kilograms of urine in rural areas, and 250 grams of feces and 1.2 kilograms of urine in urban areas. Feces not only are malodorous and considered Volumes of night soil produced for cartage and esthetically offensive in most societies, but they may treatment may be computed from the sum of the per contain an array of pathogenic viruses, bacteria, cysts capita contribution of feces and urine plus any water of protozoa, and eggs of helminths (the collective term used for ablution or for cleaning the toilet area. Daily for worms parasitic to man) that may cause disease in a night soil volumes are typically in the range of 1.5-2.0 new host. Feces are therefore the beginning of the liters per capita. Data from Kiangsu Province, China, transmission routes of the diseases considered in this show that a bucket-latrine system produces 2 liters of book; the objective of improving excreta disposal waste per capita daily, including the bucket wash water facilities is to intercept these routes at their point of (McGarry and Stainforth 1978). origin. Volumes of domestic sewage depend on quantities of water used in the home. Houses connected to sewers Qtia tities must also be connected to water systems and usually have comprehensive plumbing fittings. Such houses There are marked differences in the volumes of may, rarely, use as little as 30 liters per capita daily excreta and sewage produced by different com- (White 1977).Ifdailyusefallsbelow50literspercapita, munities. Volume, composition, and consistency of however, the sewers can lose their self-cleansing flow feces depend on such factors as diet, climate, and state and become blocked. At the other extreme, households of healih. Individual wet fecal weights vary from under with many water-using appliances (such as washing 20 grams per day to 1.5 kilograms per day. When machines and dishwashers) may use 300 or more liters national or regional averages are considered, however, per capita daily. Europeans and North Americans produce daily The consistency or solids content of night soil may between 100 and 200 grams, whereas people in be calculated from these figures. Assume a daily fecal developing countries have average daily wet fecal weight of 250 grams per capita, with a water content of weights of 130-520 grams. Vegetarians generally have 80 percent. Further assume a daily urine production of higher fecal weights than other groups, and fecal 1.2 liters plus 0.35 liters of water for anal cleansing per weights in rural areas are higher than in towns. capita. The night soil of one individual then, will Children, adolescents, and the elderly produce lower contain 50 grams of solids in 1.8 liters of night soil; in ELEMENTS AND HEALTH RISKS 5 Table 1-1. Fecal weights around the world Daily wetftcal weight (grams) Number of Country Population' subjects Auerage Range Sourceb India Nurses 13 155 ND Burkitt, Walker and Painter (1972. 1974) Less than 15 years old in New 36 374 50-1060 Tandon and Tandon (1975) Delhi More than 15 years old in New 514 311 19-1505 Ibid. Delhi Kenya Hospital staff in rural area 16 520 300->500 Cranston and Burkitt (1975) Malaysia Chinese Urban 1 227 180-270 Balasegaram and Burkitt (1976) Rural 10 489 386-582 Ibid. Malays Rural 10 465 350-550 Ibid. Indians Urban 5 170 110-240 Ibid. Rural 8 385 255-520 Ibid. Doctors Urban 6 135 40-300 Ibid. Peru Rural Indians 20 325 60-650 Crofts i1975) South Africa Rural Schoolchildren (black, age 9-12 32 16 ND Walker (1975) years) (dry weight) Schoolchildren (black) 500 275 150-350 Burkitt, Walker and Painter (1972, 1974) Urban Schoolchildren (black) 500 165 120-260 Ibid. Tertiary students (white) 100 173 120-195 Ibid. Uganda Teenage boarding school pupils 27 185 48-348 Burkitt, Walker and Painter (1972, 1974) Villagers 15 470 178-980 Ibid. United Kingdom Naval recruits and wives 15 104 39-223 Burkitt, Walker and Painter (1972, 1974) Teenage boarding school pupils 9 110 71-142 Ibid. Vegetarians 24 225 71-488 Ibid. Hospital patients (fiber added to 6 175 128-248 Ibid. diet) Laboratory staff 4 162 123-224 Greenberg (1976) Medical students 33 132 ND Cummings (personal communication) Medical staff (age 22-36 years) 11 107 60-182 Goy and others (1976) United States Cincinnati, Ohio 5 115 76-148 Connell and Smith (1974) Philadelphia, Penn. Black students 10 148 ND Goldsmith and Burkitt (1975) White students 10 192 ND Ibid. San Francisco, Calif. Medical staff 5 91 ND Gray and Tainter (1941) Norwalk, Conn. Volunteers (age 23-47 years) 6 103 49-160 Fuchs, Dorfman and Floch (1976) ND. No data. Source: John Cummings (British Medical Research Council's Dunn Nutrition Unit, University of Cambridge) compiled the information contained in the table. a. Subjects were on ad fib. diets except where indicated b. Full citations of sources in this and subsequent tables appear in the reference lists. 6 HEALTH HAZARDS OF EXCRETA other words, a solids content of 2.8 percent. If paper is whatever BOD5 contribution is made by the paper or used for anal cleansing, the solids content will increase other material used for anal cleansing. In the United to around 5 percent. The solids content of night soil is States, Laak (1974) has found that urine contains 8.6 therefore similar to that of primary sewage works grams of BOD5 per liter and that feces contain 9.6 grams sludge. Data from Japan, the island of Taiwan, and of BOD5 per 100 grams. As fecal weights increase and Thailand indicate a solids content for night soil in the moisture content rises, the BOD5 contribution per unit range 2.0-4.2 percent, with mean figures of 2.7-3.7 weight of wet feces clearly will fall. In addition, it is percent (Pescod 1971). possible that higher fecal weights will be associated with a higher fiber content that may not be readily Chemical composition biodegradable, causing the higher fecal weights to be accompanied by lower BOD5 contributions per unit Excreta, especially feces, are of complex and variable weight of dry feces. composition. Typical figures of some constituents are Possible ROD5 contributions at different fecal given in table 1-2. Of particular interest to the sanitary weights are given in table 1-3. These are speculative engineer are the data on carbon and nitrogen content calculations and require confirmation by field testing. indicating that the C:N ratio in feces is in the region of Laak (1974) has found that the daily BOD5 contri- 8, whereas in urine it is under 1. These figures have bution of toilet paper in the United States is 3.5 grams considerable bearing on the design of composting per capita, and this figure may be lower in some systems in which the C:N ratio must be around 20-30 developing countries where water or non- for the process to proceed efficiently (Gotaas 1956). biodegradable material is used. Where heavy paper Of equal importance to the public health engineer is (cement bags or newspaper), corncobs, or leaves are the concentration of organic material, measured by the used, however, the contribution of anal cleansing biochemical oxygen demand (BOD) or other similar material may be as in the United States. Figures have index (such as chemical oxygen demand, or total been added in table 1-3 to account for the contribution organic carbon).' In a night soil system, the per capita of anal cleansing material to the BOD5 in night soil. BOD5 contribution is equal to the BOD5 in excreta plus If a total daily volume of excreta and anal cleansing material of 1.5 liters per adult is assumed, it is possible to calculate the BOD5 strength of adult night soil (table Table 1-2. Composition of human feces 1-3). Although the weights of BOD5 for children will be and urine lower, the volumes will also be lower, so that the concentration will be similar to that for adults, and the Approximate composition final night soil strength may be as calculated. Pradt (percent of dry weight) (1971) found a night soil BODs content of 10,000 milligrams per liter in Japan, and Hindhaugh (1973) Constituent Feces Urine found 46,000 milligrams per liter of HOD5 in night soil in Lagos, Nigeria. This last figure is extremely high and Calcium (CaO) 4.5 4.5-6.0 may reflect the practice in Lagos of disposing of Carbon 44-55 11-17 garbage in the night soil buckets.2 However, the daily Nitrogen 5.0-7.0 15-19 volume of night soil produced in Lagos is about 1.5 Organic matter 88-97 65-85 Phosphorus (P205) 3.0-5.4 2.5-5.0 liters per capita, the figure assumed in table 1-3. Potassium (K20) 1.0-2.5 3.0-4.5 In a sewerage system the per capita BOD5 contribution is augmented by sullage, which contains Source: Adapted from Gotaas (1956). organic wastes and thus will also exert an oxygen demand. Typical figures for sewage that includes sullage are presented in table 1-4. Further data on the 1. The BOD is the mass of oxygen required by microorganisms to BOD5 in sullage can be found in the section oxidize the organic content of the waste. It is an indirect Characteristics of Sullage" in this chapter. measurement of the concentration of biodegradable material present. BOD5 denotes the oxygen demand exerted during the standard test, which is conducted at 20'C over 5 days. The chemical 2. Garbage may be placed in the night soil buckets because of the oxygen demand is the mass of oxygen consumed when the organic lack of an adequate refuse disposal system. Huponu-Wusu and matter present is oxidized by strong oxidizing agents in acid solution. Daniel (1977) found that only 39 percent of 1,099 randomly sampled It includes some substances (such as cellulose) that are not available households in metropolitan Lagos are reached by the refuse to microorganisms but excludes some (such as acetic acid) that are. collection service of the city council. Table 1-3. Possible standard biochemical oxygen demand (BOD5) content of excreta and night soil BOD5 content Assumed Per adult Strength Assumed adult urine Estimated In wet Total in anal- oJ night adultfecal weight water feces Per adult Per adult per adult cleansing soil weight (kilograms in feces (0 I" I I infeces in urine in excreta material ( Population (grams daily) daily) (percent) per gram)b (grams da,i l (grams daily) (grams daily) (grams daily) per liter)c Europe and North America 150 1.2 75 96d 14.4 10.3 24.7 3.5d 18,800 Developing country Urban 250 1.2 80 77 19.3 10.3 29.6 3.0' 21,700 Rural 350 1.2 85 58 20.3 10.3 30.6 2.0' 21,700 Notes: This table is speculative and should not be used if actual data are available. a. Fecal weights are taken from the ranges given in table 1-1. b. Calculated by assuming that the BOD5 contribution is constant per unit weight of dry feces. This assumption is unlikely to be accurate because the proportion offiber will increase as fecal weight increases, and fiber is not readily biodegradable. c. Assuming that 1.5 liters are produced by each adult daily. d. From Laak (1974). e. Where water is used for anal cleansing, this figure will be 0. Table 1-4. BOD5 contributions per capita in urban sewage BOD, per capita daily Country or region in sewage (grams) Brazil (Sao Paulo) 50 France (rural) 24-34 India 30-55 > Kenya 23-40 > Nigeria 54 Southeast Asia 43 o United Kingdom 50- 59 United States 45-78 Zambia 36 D Note: These figures were calculated by measuring the BOD5 of raw sewage and multiplying it by the estimated daily water use per capita. This gives a most approximate result because urban sewage may contain a substantial proportion of commercial andindustrial wastes. Domestic water use and BoD5 contributions are not readily derived from data on total urban sewage, and these figures arc not directly comparablc with those in table 1-3. ELEMENTS AND HEALTH RISKS 9 Pathogens in exereta (listed in table 1-5) are particularly important- Part Two of this work contains detailed information adenoviruses, enteroviruses (including poliovirus), about the organisms causing human excreta-related hepatitis A virus, reoviruses and diarrhea-causing diseases; however, a brief summation here of the major viruses (especially rotavirus). Other virus groups are disease agents examined in Part Two may be of also found in feces. Infections with all of these, diseae agets exmine in Prt Tw may e of especially in children, are often subclinical. assistance. Four groups of pathogens-viruses, bac- -sregards theden, tero subelimstpli teria, protozoa, and worms-cause these diseases. In i s r d nte risest any i ica . inss addition, excreta disposal may favor the breeding of Sometimes howeverinecto an lead ild insects, particularly mosquitoes, flies, and cockroaches, inlenikes, illessr, tirs eti s,"nor to mild which will always have Duisance value aDd may act as ifunalk lns,t vrsmnnii, rt whchrs wil humalysehave niagence vhaluetan may acts s paralytic poliomyelitis, which may lead to permanent vectors of human disease agents that may themselves diailt or det.I.setmtdta aayi no be fon in fee *ruie disability or death. It iS estimated that paralytic not be found in feces or urine. poliomyelitis occurs worldwide in only about I out of every 1,000 poliovirus infections, but most children VIRUSES IN EXCRETA. Numerous virusesm in fect become infected in developing countries, and con- thernesina treyact andfet passedmin ,th fe sequently the number of paralysis cases can be high. wherupontheymay nfec newhuma hoss by Echovirus and coxsackievirus infections can cause a ingestion or inhalation. One gram of human feces may contain i09 infectious virus particles, regardless of wide range of diseases and symptoms including simple whether the individua is experiencing any d e fever, meningitis, respiratory illness, paralysis, myocar- whether the individual IS experiencing any discernible diis an.te .oniin se hpe ) illness. Although they cannot multiply outside a d otis, and other viruses apr f i e suitable~~~~~ ~~~~ hscelthexrtdvrssmasviefr Rotaviruses, and other viruses, are found in the feces sutal .hs 'cl,hecetdvuemy s f of a large number of young children suffering from many weeks in the environment, especially if diarrhea and are another important group of excreted temperatures are cool ( <15°0C). Concentrations of 10 .. . viruses. Their precise causative role and epidemiology infectious particles per liter of raw sewage have been remain uncertain, but they are responsible for a reported, and excreted viruses can be readily isolated substantial roportion of diarrhea episodes amon from soil and natural waters at sites which have been c tphpt g young children in many countries (see chapter 11). exposed to fecal discharges (World Health Organiz- Hepatitis A virus is the causative agent of infectious ation 1979). Five groups of pathogenic excreted viruses hepatitis. Infection may lead to jaundice but, especially in young children, is often symptomless (see chapter 3. The term "excreted virus' is used here for comparability with 10). "excreted bacterium," "'excreted helminth," and so on. "Excreted virus" is synonymous with "enteric virus," which must be distinguished from the genus Enterovirtus, which includes polio-, BACTERIA IN EXCRETA. The feces of a healthy person echo-, and coxsackieviruses. contain large numbers of commensal bacteria of many Table 1-5. Viral pathogens excreted injeces Can Chapter symptomless containing infections detailed Virus Disease occuir? Reservoir information Adenoviruses Numerous conditions Yes Man 9 Enteroviruses Polioviruses Poliomyelitis, paralysis and other Yes Man 9 conditions Echoviruses Numerous conditions Yes Man 9 Coxsackie viruses Numerous conditions Yes Man 9 Hepatitis A virus Infectious hepatitis Yes Man 10 Reoviruses Numerous conditions Yes Man and 9 animals Rotaviruses, Norwalk agent and Diarrhea Yes Probably II other viruses man Note: See table 9-1 for more information. 10 HEALTH HAZARDS OF EXCRETA species. The species of bacteria found in the normal are at risk, but the patient is not disseminating bacteria stool, and the relative numbers of different species, will in the community. A paticnt with a mild case, or a vary among communities. The bacteria most com- carrier, by contrast may look relatively healthy and be monly found and an indication of the variations in mobile while excreting up to 106 chloera vibrios per their concentrations in feces are given in table 1-6. gram of feces. In some infections the carrier state may Because these bacteria are ubiquitous and numerous in last for a duration similar to the illness itself, but in the feces of healthy people, they have been used as others it may persist for months or even a lifetime. indicators of fecal pollution.4 The most widely used Some carriers may show symptoms of illness and indicator has been the fecal coliform Escherichia coli, continue to excrete the bacteria, whereas others may be the main constituent of the "enterobacteria" group in healthy throughout infection. A carrier becomes table 1-6, but enterococci (or, more generally, fecal especially dangerous when engaged in food prepara- streptococci), another widespread commensal group, tion or handling or in water supply. are also used as indicators. Anaerobic bacteria also, Some of the pathogens listed in table 1-7 are excreted such as Clostridium, Bacteroides, and Bifidobacterium, entirely (or almost entirely) by man, but others are have served as indicators, and their potential value as excreted by a wide range of animals. This fact limits indicators is currently attracting increased attention disease control through improvements in human (Evison and James 1977). excreta disposal alone, because any changes made will On occasion, some bacteria listed in table 1-6, or likely not affect transmission of pathogens from animal their particular strains, may give rise to disease, as may feces to humans. Three of the major infections listed in other groups of bacteria normally absent from the table 1-7 (typhoid, shigellosis, and cholera), however, healthy intestine. These pathogenic, or potentially are assumed to be exclusively human infections, whose pathogenic, bacteria are listed in table 1-7. They most spread is from one person to another. commonly enter a new host by ingestion (in water, on In summary, all the viral and bacterial pathogens food, on fingers, in dirt), but some may also enter listed, respectively, in tables 1-5 and 1-7 are passed in through the lungs (after inhalation of aerosol particles) the feces of man or animals; they are not free living.5 or through the eye (after rubbing the eye with fecally Infection of a new host normally follows ingestion of contaminated fingers). At some time during the course the pathogens and because transmission is primarily of an infection, large numbers of the bacteria will be through the swallowing of minute quantities of infected passed in the feces, thus allowing the spread of infection feces, the sanitary disposal of all feces (both human and to new hosts. animal) and perfect personal hygiene would largely Diarrhea is a major symptom of many bacterial eliminate these diseases. For many infections, this has intestinal infections. The bacteria may also invade the unfortunately proved an unattainable goal in even the body from the gut and cause either generalized or most affluent societies, and so a more modest target localized infections. This invasion is characteristic of than eradication must be set: the reduction of typhoid infections and other enteric fevers caused by transmission to a manageable level. salmonellae. During infections restricted to the gut, Bacteria of the genus Leptospira have been excluded bacteria will be passed only in the feces. When invasion from the discussion above because they cannot be has occurred, bacteria may be passed in the urine as included in the generalizations made. Although well and will also be found in the bloodstream at some leptospirosis in the majority of human cases gives rise stage. to a benign, self-limiting, febrile illness, it occasionally A carrier state exists in all the infections listed in leads to severe, even fatal disease characterized by table 1-7. Thus, in communities where these infections jaundice and hemorrhage (Weil's syndrome) where- are endemic, a proportion of perfectly healthy upon death may result from kidney failure. Leptospira individuals will be excreting pathogenic bacteria. are excreted in the urine of animal carriers, and usually These carriers play a prominent role in transmitting reach new animal and human hosts through skin the infection they carry because they are mobile, abrasions or mucous membranes contaminated by dispersing their feces widely. Cholera provides an infected urine. Man may be an intermittent carrier for a example of the problem. A patient with severe cholera few weeks (rarely months) after an acute infection. will be in bed for most of the time he or she is excreting Leptospirosis is considered here because of the risk to Vibrio cholerae. Those who nurse the patient clearly workers who handle excreta, which may contain leptospires either from animal carriers (for example, 4. The use of indicator organisms is discussed in more detail in chapters 4 and 13. 5. This may not be true for Vibrio cholerae; see chapter 17. Table 1-6. Bacterial microflo7a of humanfeces by national diet Number of bacteria infeces (mean log,0 per gram) National Entero- Bifido- diet Country bacteriaa,b Enterococcib Lactobacilli Clostridia Bacteroides bacteria Eubacteria Largely Guatemala 8.7 7.9 9.0 9.3 10.3 9.4 ND m carbo- Hong Kong 7.0 5.8 6.1 4.7 9.8 9.1 8.5 i m hydrate India 7.9 7.3 7.6 5.7 9.2 9.6 9.5 m Japan 9.4 8.1 7.4 5.6 9.4 9.7 9.6 - Nigeria 8.3 8.0 ND 5.9 7.3 10.0 ND > z Sudan 6.7 7.7 6.4 4.9 7.8 8.5 ND Uganda 8.0 7.0 7.2 5.1 8.2 9.4 9.3 Mixed Denmark 7.0 6.8 6.4 6.3 9.8 9.9 9.3 _ Western England 7.9 5.8 6.5 5.7 9.8 9.9 9.3 Finland 7.0 7.8 8.0 6.2 9.7 9.7 9.5 m Scotland 7.6 5.3 7.7 5.6 9.8 9.9 9.3 United States 7.4 5.9 6.5 5.4 9.7 9.9 9.3 ND. No data. Sources: England, India, Japan, Scotland, United States, Uganda (Drasar 1974); Denmark, Finland (International Agency for Research on Cancer 1977); Hong Kong (Crowther and others 1976); Nigeria, Sudan (Draser, personal communication); Guatemala (Mata, Carrillo and Villatoro 1969). a. This group mainly contains Escherichia coli. b. These two groups are the most commonly used fecal indicator bacteria. 12 HEALTH HAZARDS OF EXCRETA Table 1-7. Bacterial pathogens excreted in feces Caln Chapter svllptoinless containing illect ion detailed Bacterium Disease occU r? Reservoir informnation Campylobacrer fetus ssp. jejoiii Diarrhea Yes Animals and man 12 Pathogenic Escherichia colia Diarrhea Yes Man' 13 Sulmonella S. typhi Typhoid fever Yes Man 15 S. paratyphi Paratyphoid fever Yes Man 15 Other salmonellae Food poisoning and other Yes Animals and man 15 salmonelloses * ..: spp. Bacillary dysentery Yes Man 16 Vibrio 1: chlolerae Cholera Yes Man 17 Other vibrios Diarrhea Yes Man 17 Versinia enterorolitica Diarrhea and septicemia Yes Animals and man' 18 a. Includes enterotoxigenic, enteroinvasive, and enteropathogenic E. coli. b. Although many animals are infected by pathogenic E. coli, each serotype is more or less specific to a particular animal host. c. Ofthe 30 or more serotypes identified so far, a number seem to be associated with particular animal species. There is at present insufficient epidemiological and serological evidence to say whether distinct serotypes are specific to primates. the sewer rat, Raittus norcegicus) attracted to such agent of human onchocerciasis, or river blindness), are environments or, occasionally, from infected people. not considered.6 Helminths (except for Strongyloides) do not multiply PROTOZOA IN EXCRETA. Many species of protozoa within the human host, and this is of great importance can infect man and cause disease. Among them are in understanding their transmission, the ways they several species that are harbored in the intestinal tract cause disease, and the effects of environmental changes of man and other animals, where they may cause on their control. Helminthic disease is not an all-or- diarrhea or dysentery. Infective forms of these nothing phenomenon. In infections due to viruses, protozoa are often passed as cysts in the feces, and man bacteria and protozoa, where massive asexual repro- is infected when he ingests them. Only three species of duction occurs within the host, once infection occurs its human intestinal protozoa are considered to be severity cannot be related easily to the infecting dose of frequently pathogenic: Giardia lamiblia, Balanitiduntl organisms. One either has measles, or a common cold, coli, and Entamoeba histolytica (see table 1-8). An or not and it is not meaningful to say that someone has asymptomatic carrier state is common in all three and, 'a lot of measles"'. By contrast, with helminthic in the case of Entamoeba histoltica, it is carriers who infections it is essential to think quantitatively. The are primarily responsible for continued transmission. HELM4INTHSIN EXCRETA. Many species of parasitic 6. An exception, discussed in detail in chapter 36, is the HELMtNHS tN XCRETA Many peciesof parsitic bloodborne larva of the filarial worm causing elephantiasis. which worms, or helminths. have human hosts. Some can may be transmitted by Ctlex pipiens mosquitoes. which breed in cause serious illnesses, but a number generate few sewage, sullage. and other polluted waters. Culex pipiens is a complex symptoms. Only those helminths whose eggs or larval of mosquito species and subspecies. The main tropical species. and forms are passed in the excreta are of concern to this the major vector of filariasis in those tropical areas where the infection is Culex-transmitted. is Culex quinquejasciatus (previously study. Only Schistosorala hcaematobitan7l (the agent of also known as Culex pipiens latigan.s. C.p. quinquejasciutus. or C. urinary schistosomiasis) is voided in the urine: Jatigats(. Other important species are C.p. pipien., C.p. ozolestus (the the others examined are all excreted in the leces. vector of filariasis in Egypt), and C.p. pallens. More details on the The helminths that begin a new cycle of transmission complex are provided in chapter 36. 'Culex pipiens" will be used by escaping from a blister on the carrier's skin (guinea throughout the text unless a particular member of the complex is being referred to. Because they are not specifically associated with wormn Dracunculus mediulensis), or by entermg the excreta, othcr inscctborne pathogens (such as trypanosomes and body of a blood-feeding insect to be transmitted I. ,... ... i their vectors, and the diseases they cause are excluded through its bite to a new host (Onchocerca volvulus, the from the purview of this study. ELEMENTS AND HEALTH RISKS 13 Table 1-8. Protozoal pathogens excreted infeces Can Chapter symnptomlness containing infections detailed Proto-oon Disease occur? Reservoir information Balantidium Diarrhea, dysentery and colonic Yes Man and animals (especially pigs 19 coli ulceration and rats) Entamoeba Colonic ulceration, amebic histolvtica dysentery, and liver abscess Yes Man 20 Giardia Diarrhea and malabsorption Yes Man and animals 21 lamblia question is not just whether or not someone has a Because of this quantitative characteristic, the hookworm infection but how many worms has he (in development of pathology in helminthic infections is other words, how "heavy" or "intense" is the infection). usually the result of cumulative worm burdens, often Sometimes worm burdens can be determined by carried over many years as a product of regular and purging the patient immediately after an anthel- repeated reinfection. This further contrasts with the minthic, but more usually the output of eggs in the asexually replicating organisms, which may cause an exereta is determined and used as an index of the overwhelmingly heavy infection and a state of gross intensity of infection. Even though there is a good deal disease within a few days or weeks after a single of variation from day to day, the relation is valid at infective dose enters the body. community level and in any case the egg output is The excreted helminths are listed in table 1-9. Often always a better measure of transmission and the developmental stages through which they pass sometimes a better guide to pathology than the burden before reinfecting man, their life cycles, are very of adult worms. complex (as is shown in the table). The helminths are Worm burdens and levels of egg output are not evenly classified in two main groups: the roundworms or randomly distributed among their human hosts, and (nematodes) and those worms that are flat in cross- within any sex and age group of an infected community section. The flatworms again form two groups: the there will be a few people who are carrying a heavy tapeworms (cestodes), which form chains of helminth worm burden and a much larger number with light 'Isegments," and the flukes (trematodes), which have a intensities of infection. In general, the risk of illness and single flat, unsegmented body. The roundworms may its severity increases with the worm burden. It is cause mechanical obstruction (Ascaris), rectal pro- therefore common in helminth infections to find many lapse (Trichuris), itching around the anus (Enterobils), of the community infected, occasional people (often or anemia (hook-worms). They also divert food to with heavy infections) ill, and a few dying. It is themselves and produce abdominal pain in some cases relatively easy to see the public health importance of (many cases, however, are symptomless). Adult the heavy infections but far harder to assess disability tapeworms create health problems mainly by depriving in the lightly infected majority where consequences are their host of nutrients. Of the trematodes, some inhabit likely tobe nonspecific andeffects cumulative with those and damage the liver (Clonorchis) or lungs (Paragoni- from other infections. nizis). The schistosomes live outside the intestine in The number of heavy infections is not simply small blood vessels; their eggs that fail to escape from proportional to the prevalence of infection. At high the host may damage several organs. The intestinal prevalences, increased transmission will tend mainly to flukes may occur in large numbers, are mostly push up the proportion of heavy infections while at low transmitted through food, and cause relatively mild prevalences there may be few people heavily infected symptoms. and the number may change little with transmission. Most of the roundworms infecting man, and also the Where immunity acquired by the host is unimportant, a schistosome flukes, have separate sexes, so that reduction in transmission due to control of excreta transmission depends upon infection with both male may reduce the number of heavy infections and so and female worms and upon the meeting, mating, and reduce the burden of disease even if it affects the egg production of these worms within the human body. prevalence of infection rather little. A number of individuals may be infected with a single Table 1-9. Helminthic pathogens excreted infeces Chapter containing detailed Helminth Common name Disease Transmission Distribution information Ancylostoma Hookworm Hookworm Man -* soil -man Mainly in warm 22 duodenale wet climates N Ascaris Round worm Ascariasis Man -, soil -- man Worldwide 23 hlimbr icoides Clonorchis Chinese liver Clonorchiasis Man or animal -* Southeast Asia 24 sinensis fluke aquatic snail -* fish -+ man Diphyllobothrium Fish Diphyllobothriasis Man or animal - Widely distributed foci. 25 latum tapeworm copepod - fish - man mainly temperate regions Enterobius Pinworm Enterobiasis Man - man Worldwide 26 vermicularis Fasciola Sheep liver Fascioliasis Sheep -- aquatic snail -; Worldwide in sheep- 27 hepatica fluke aquatic vegetation - and cattle-raising man areas Fasciolopsis Giant intestinal fluke Fasciolopsiasis Man or pig -- aquatic Southeast Asia, 28 buski snail -- aquatic mainly China vegetation -- man Gastrodiscoides n.a. Gastrodiscoidiasis Pig - aquatic snail - India, Bangladesh, 30 hominis aquatic vegetation - Vietnam, Philippines man Heterophyes n.a. Heterophyiasis Dog or cat -+ brackish- Middle East, 30 heterophyes water snail -- brackish- southern Europe, water fish -- man Asia Hymenolepis nana Dwarf tapeworm Hymenolepiasis Man or rodent - man Worldwide 29 Metagonimus n.a. Metagonimiasis Dog or cat -- aquatic East Asia, 30 yokogawai snail -+ freshwater Siberia (USSR) fish -+ man Necator amnericanus Hookworm Hookworm Man -* soil -+ man Mainly in warm 22 wet climates Opisthorchis Cat liver Opisthorchiasis Cat or man -+ aquatic USSR, 24 felineus fluke snail - fish -. man Thailand 0. viVerrini n.a. Paragoniimus Lung fluke Paragonimiasis Pig, man, dog, cat, or Southeast Asia, 31 westernnani other animal -- aquatic scattered foci in Africa snail -+ crab or cray- and South America fish -> man Schistosorna Schistosome Schistosomiasis; Man -- aquatic snail -+ Africa, Middle East, 32 haemnatobiunt bilharziasis man India S. japonictan Animals and man -* Southeast Asia 32 snail -- man S. rnansoni Man -+ aquatic snail -, Africa, Middle East, 32 man Central and South America Strongyloides Threadworm Strongyloidiasis Man -- man Mainly in warm 33 m z stercoralis wet climates Taenia saginata Beef tapeworm Taeniasis Man -,cow --man Worldwide 34 T solium Pork tapeworm Taeniasis Man -'pig Worldwide 34 (or man) man > Tricihuris Whipworm Trichuriasis Man - soil -+ man Worldwide 35 H trichiura n.a. Not applicable. 16 HEALTH HAZARDS OF EXCRETA sex or with unmated worms. These cases are of no for a period of about 4-6 weeks; chronic human epidemiological significance because they do not carrier states are rare. transmit infection. Magnitude of patlhogen excretion Characteristics of Sullage We can dramatize the magnitude of the potential Sullage. also known as gravwater, is domestic health hazard from excreta by considering a typical wastewater not containing excreta-the water discar- load of pathogens excreted by a poor tropical ded from baths, sinks, basins and the like that may be community in a single day. Estimated data on the more expected to contain considerably fewer pathogenic prominent diseases threatening public health and the microorganisms than sewage. Interest and research in large fecal volume, often containing significant the handling of sullage has increased in recent years, concentrations ofpathogenic organisms, produced in a both in developing and affluent countries. In affluent hypothetical community are given in table 1-10. countries there is growing interest in the use of Excreta-related diseases account for some 10-25 sewerless chemical toilets and separate sullage disposal percent of illnesses that reach the health care services, as a way of overcoming environmental problems and cause a vast amount of misery that goes associatedwiththedisposaloflargevolumesofheavily unreported. Given the dangers of poor sanitation, it is contaminated sewage from urban areas. There is also crucial that the engineering profession and the interest in chemical toilets and on-site sullage disposal appropriate governmental agencies of the world take for use in nature parks, where environmental seriously the responsibility to collect, transport, treat, considerations are paramount (Winneberger 1974). and reuse human waste substances in ways that do not There is also a growing realization in developing endanger the public. countries of the financial and other difficulties associated with providing waterborne sewerage sys- tems, and consequent increased interest in dry or on- site techniques such as improved pit latrines, In general, urine is a sterile and harmless substance. composting toilets or cartage systems (Kalbermatten There are, however, occasions when host infections and others 1982). Some of these sewerless technologies cause passage of pathogens in the urine. The three require the separate disposal of sullage when the principal infections leading to the significant ap- volumes of domestic wastewater become too great pearance of pathogens in the urine are urinary simply to drain away in the yard. Furthermore, a schistosomiasis, typhoid, and leptospirosis. Coliform worldwide awareness is dawning that it is extravagant and other bacteria may be numerous in the urine to use up to half of a household's high quality drinking during cystitis and other urinary infections, but they water just to flush excreta along sewers. The need to constitute no public risk. In venereal infections the design a sullage disposal system accompanies the microbial agents will also reach the urine, but they are development of any toilet not flushed by water. so vulnerable to conditions outside the body that excreta are unimportant vehicle of transmission. People infected with urinary schistosomiasis (caused Quantities by Schistosonia haematobium) will pass eggs chiefly in Sullage volumes depend upon domestic water use. their urine. The worms live for years (occasionally Where people use public taps, daily domestic water use decades) and superinfection occurs, so that those may be as low as 10 liters per capita (White 1977). In affected may pass eggs-sometimes accompanied by affluent households with full plumbing, daily water use blood-for much of their lifetimes. In heavy infections, may be 200 or more liters per capita, and all water not 10 millilitres of urine may contain over a thousand eggs used for flushing toilets may be classed as sullage. if the urine is collected near to midday, when eggs are Bennett, Linstedt and Felton (1974). studying homes in most numerous. During the phase of typhoid and the United States. found that the toilet was used 3.6 paratyphoid fevers when bacteria are disseminated in times daily per capita, that the average flush used 15 the blood, the organisms will usually be shed in the liters, and that toilet flushing accounted for 33 percent urine. In cases where S. haematobiunm is also present, of domestic water use. Witt. Siegrist and Boyle (1974), however, prolonged urinary carriage of typhoid may also studying homes in the United States, found occur over many years. An individual with lepto- corresponding figures of 2.3 times daily per capita, 15 spirosis will pass Leptospira intermittently in the urine liters for flush, and 22 percent of water use allocated to Table 1-10. Possible output of se/ected ,'- o H1 in thc feces and sewage o.j]a tropical communitY of 50,000 in a developing counlry prevalence of Average tnumbei oj infection in country organisms per grain 7Ttal excreted daily Concentration per Pathogen I j0. 'il of ffees6 pe- injected persoit lotal excreted dailY by town liter in town sevagd' Viruses Etterorirusesd 5 10o 1o8 2.5 x 101 5,000 Bacteria Pathogenic E. colie lo ,0 10'° ? ? Salmonella spp. 7 106 lo, 3.5 x 10" 7,000 *, spp. 7 106 lo, 3.5 x 101 7.000 l'ibrio cholerae 106 io8 5 x 10i' 1.000 m rn Protozoam Elntatnioeba hiseoirtica 30 15 x 10 15 x 10" 2.25 x 1011 4,500 Z Helmintbs > .Ascoaris lun,bricoides 60 lo4O 10" 3 x 10'° 600 Hookworms" 40 800o 8 x 104 1.6 x 109 32 Schistosomoa rnOtlsoIli 25 40' 4 x 103 5 x 107 1I Toaenic saginiata 1 104 106 5 x 108 10 Irichliris trichiura 60 2 x 10a 2 x 105 6 x109 120 C4 '? Uncertain. Note: [his table is hypothetical, and the data are not taken from any actual, single town. For each pathogen, however, the figures are reasonable and congruous with those tound in the literature. The concentrations derived for each pathogen in sewage are in line with higher figures in the literature, but it is unlikely that all these infections at such relatively high prevalences would occur in any one community. a. The prevalences given in this column refer to infection and not to morbidity. b. It must be recognized that the pathogens listed have different abilities to survive outside the host and that the concentrations of some of them will rapidly decline after the feces have been passed. The concentrations of pathogens per liter in the sewage of the town were calculated by assuming that 100 liters of sewage are produced daily per capita and that 90 percent of the pathogens do not enter the sewers or are inactivated in the first few minutes after the excretion. c. To calculate this figure it is necessary to estimate a mean fecal weight for those people infected. This must necessarily be the roughest of estimates because of the age-specific fecal weights and the age distribution of infected people in the community. It was assumed that people over 15 years old excrete 150 grams daily and that people under 15 excrete, on average, 75 grams daily. It was also assumed that two-thirds of all infected people are under 15. This gives a mean fecal weight for infected individuals of 100 grams. d. Includes polio-, echo-, and coxsackieviruses. e. Includes enterotoxigenic, enteroinvasive, and enteropathogenic E. coli. f. The distribution of egg output from people infected by these helminths is extremely skewed; a few people excrete very high egg concentrations. g. Ancvlostoma diuodeniale atid Necator uriericanus. 18 HEALTH HAZARDS OF EXCRETA flushing. Reviewing data from several studies, Witt and 1974). The sullage contributed 53 percent of the sewage colleagues found that water from toilet flushing was flow, 52 per cent of the BOD5, 43 percent of the chemical between 22 and 45 percent of the total domestic water oxygen demand, about 15 percent of the nitrogen, and usage. Laak (1974) reviewed data from Canada, 45 percent of the phosphates. The data in table 1-12 Sweden, and the United States that show the following further indicate that, if the ratio of chemical oxygen percentage allocations of water use in houses with full demand to BOD5 is used as the criterion, toilet wastes plumbing: are more resistant to biodegradation than sullage. Meani Range Hypes (1974) points out the effect of sink-installed Bathroom 26 12-40 garbage disposal units on the quality of sullage. In his Kitchen 9 5-16 ~~~~~~~test, sullage had a BOD5 of 328 milligrams per liter Kitchen 18 5-16 when without garbage solids and 480 milligrams per Tolanr 18h 4t-2 liter when with garbage. Another report found that in Toilet flushing 47 41-65 Taipei, sullage contributed 40 percent of BOD5 in We have been unable to obtain comparable figures sewage (but in Taipei, scraps were fed to pigs rather from urban households, either with or without sewer than washed down the sewers; World Health connections, in developing countries. Data for rural Organization 1970). households without sewers, however, are available, and Witt, Siegrist and Boyle (1974) examined the examples of water use allocations in Lesotho, Papua bacterial content of sullage in the United States. Their New Guinea, and Uganda are given in table 1-11. results,summarizedintablel-13,showthatwaterused These figures highlight the immense differences in for bathing and showering became less contaminated water use practice, and thus in the kind of sullage with fecal bacteria than water used in washing clothes. produced, in areas varying in culture, environment, Furthermore, 38 percent of the total fecal streptococcal wealth, and other factors. The health implications of isolates were enterococci (Streptococcuis Jaecalis, S. sullage disposal will depend on the technologies used, faecium, and S. duranis); the majority of the bath water which in turn must consider such variables as the enterococci were S. faecalis var. Iiquefaciens (in household volume of sullage, density of housing, local contrast, only a few enterococci isolated from the climate, soil type, and groundwater conditions. clothing waters were of this species, now widely regarded as being nonfecal in origin). S. bovis, a primnarily nonhuman species, accounted for 22 percent Composition of all streptococcal isolates. These findings suggest that The results of surveys of five households in the under half of the streptococci isolated were from United States are shown in table 1-12 (from Laak human feces, and that the bath water was even less Table 1-11. Allocation of water use in sewerless rural households in developing countries Couitry Uganda Papua New Guinea Water use Lesotlio (Enga Province) Lango Kigezi Average total daily use per capita (liters) 18 0.68 18 8 Bathroom (personal hygiene) (percent) 15 0 66 20 Laundry (percent) 22 0 Drinking Animals (percent) 2 8 0 0 Humans (percent) 45 79' 19 6' Kitchen (cooking and utensil hygiene) (percent) J 11 13 74 Vegetable gardens (percent) 6 0 0 0 Other (percent) 10 2 2 0 Sources: Lesotho (Feachem and others 1978); Papua New Guinea (Feachem 1977); Uganda (White, Bradley and White 1972). a. These are very small volumes of drinking water. In Papua New Guinea they may be due to low salt intake and consequent low fluid demand and to water intake from food, especially sugar cane. In Kigezi, Uganda. the practice of eating gruels and other high liquid foods may account for the low drinking water consumption. ELEMENTS AND HEALTH RISKS 19 Table 1-12. Pollution loads of wastewater sampledfrom various plumbingfixtures in the USA (milligrams per capita daily) Biochemical Chemical oxygen oxygen demand (BOD) demand NO3-N NH3-N P04 Wastewater source Mean Percent Mean Percent Mean Percent Mean Percent Mean Percent Bathroom sink 1,860 4 3,250 2 2 3 9 0.3 386 3 Bathtub 6,180 13 9,080 8 12 16 43 1 30 0.3 Kitchen sink 9,200 19 18,800 16 8 10 74 2 173 2 Laundry machine 7,900 16 20,300 17 35 49 316 10 4,790 40 Toilet 23,540 48 67,780 57 16 22 2,782 87 6,473 55 Total 48,690 100 119,410 100 73 100 3,224 i0oa 11,862 100, Source: Adapted from Laak (1974). a. Total percentage rounded to 100. contaminated relative to the clothing water than the coliforns and 326 fecal streptococci per 100 milliliters), total counts suggested. Hypes (1974) found that than those given in table 1-13 (Small Scale Waste coliform counts in sullage were about 1.9 x 107 per 100 Management Project 1978). milliliters irrespective of garbage content. After 24 Although data are lacking, it may be assumed that hours of storage, this count had increased to 5.4 x 108, sullage from bathrooms and laundries will contain indicating that sullage is a favorable medium for small numbers of any pathogenic viruses, bacteria, coliform growth. protozoa, or helminth eggs being excreted by the Available information on the microbiological people who use them. The washing of babies and their quality of sullage is very limited and neither of these soiled clothing may substantially raise the pathogen two data sets (Hypes 1974 and Witt, Siegrist and Boyle content of sullage. It is also possible that some bacteria 1974) may be representative. A more recent study in the find warm sullage a suitable medium for multi- USA reports lower bacterial counts in clothing wash plication. Data on the microbiological quality of water (215 total coliforms, 107 fecal coliforms and 77 sullage from the tropics might verify this possibility, fecal streptococci per 100 milliliters), and higher counts and its collection should be a priority of sanitation in bath water (1,810 total coliforms, 1,210 fecal research. Table 1-13. Bacterial content of sullage in the USA (per 100 milliliters) Total coliforms Fecal coliforms Fecal streptococci Geometric Geometric Geometric Sullage source mean Range mean Range mean Range Bath and shower water 1.100 70-(8.2 x 103) 220 1-(2.5 x 103) 44 1-(7 x 104) Clothing washwater 18,000 85-(8.9 x 105) 1,400 9-(1.6 x 104) 210 1-(1.3 x 106) Clothing rinsewater 5,300 190-(1.5 x 105) 320 35-(7.1 x 103) 75 1-(2.3 x 105) Source: Adapted from Witt, Siegrist and Boyle (1974). 20 HEALTH HAZARDS OF EXCRETA Sullage disposal and health But in areas of seasonal rainfall, and where the drains are liable to blockage and ponding, the addition of Theresal ar fiveind wastewofer sullptaglesdisposa casul sullage will create year-round standing water and thus disposal by tipping wastewater receptacles in the yard; errudClxbedn hr nysaoa garden watering on-site disposl by soakaway' year-round Culex breeding where only seasonal grardenageinto opendrain-siten draissal byto soakaw; breeding may previously have occurred. It is not, drains or sewers. Each of these has different health therefore, the quality of the sullage that poses a health drplicatinsornss. Each of these has different health risk, since ponded stormwater will also be sufficiently implications. Tipping in the yard may create breeding sites for polluted to allow Culex breeding, but the continuous insects such as Culex pipienis as well as muddy and addition of sullage to storm drains subject to ponding conditions close to the dwellings. Because it that converts wet season breeding into year-round unesanitaofery concealment, a clean, dry yard is less breeding. In this case the rise in Cutlex populations may does not offer concealment, a clean, dry yard IS less ledtinradfirassrnmsioadthso likely to be used by children for defecation, and any lead to increased filariasis transmored thus to worm eggs their feces might contain will be less likely to Aeme of isfect an be foundinearec mature (nematode eggs require a moist environment to develop).7 Sullage containing pathogens from babies' resurgence of Bancroftian filariasis as a major public bath water or adults' ablution water may also infect health problem in Egypt (Southgate 1979). Since children playing in the yard. In well-draining soils, approximately 1965 a complex of factors-including wheldren sulaynge p uion oard. hsIng w -deinsit oilslw, major changes in irrigation practice, a proliferation of where sullage production or housmig unliky to bewa poorly maintained water supplies, and inadequate tipping of sullage outside the home Is unlikely to be a exrt .dsoa faiite cotmntn.ufc excreta-dis osal facilities contaminating surface major health hazard. Where soils are less permeableg manr whereth wazaerd useore housine densis high, water-has increased C. pipiens breeding in parts of the a Nile Delta. Consequently, the prevalence, intensity, however, an adequate method of sullage disposal is and geographic spread of Bancroftain filariasis have essential. (It should be noted that high housing increased. It has also contributed to explosive densities are generally associated with poverty and epidemics of Rift Valley fever in Egypt during 1977 and thus with low water use and sullage production.) 1978 (Hoogstraal, Meegan and Khalil 1979). Sullage disposal by watering vegetable gardens near U the house is likely to create few if any health hazards, lrge-saleasulae sposal sinto oen rins whea provided that prolonged ponding of wastewater is prevented (to discourage mosquito breeding) and that tendency to blockage. Too often sullage makes its way children are dsuato streams by natural gullies, and no formally defined children are discouraged from defecating in or near the dang ytmeit.Teslto oteepolm gardens. Sullage disposal by soakaway provides a low . isae to usea. aTernative method pof lem riskof goundate conamintio; th ris of IS either to use an alternative method of sullage risk ogrudae cnaia . disposal or to prevent drains from blocking by microbiological groundwater pollution is much lower c with sullage than it is with sewage.' The same is true of g y g high nitrate pollution (as indicated in table 1-12, clear. The latter approach is the more realistic and ' labor intensive and can be Implemented by the sullage contains little nitrogen compared with sewage). empl oyent o nicia we bypsubcntractin Drainage of wastewater into open drains, perhaps temjobet ot privat sor,eor by sorgani inga into~ ~ ~ ~~~. str dris.rvdstems edl the Job to the private sector, or by organizing and into~~~~ str dris prvdstems.edl motivating community effort on a neighborhood basis. identifiable health risk, namely that of promoting the breeding of C. pipiens and other mosquitoes. In areas of Finally, sullage may be disposed of into a sewerage system, as is sewage, except that smaller-bore pipes are yer-ondrinal,str daiswilcotanwae used. This means of disposal raises no special health continuously. If they are kept free of garbage and are poems and onvnional ratment beforeadis well designed, the drains will flow freely and provide few sites for mosquito breeding, and the presence or charge or reuse should be highly effective. The load of absence of sullage will not affect community health pathogenic microorganisms in sullage will be small, so that discharge or reuse can take place without tertiary 7. Some of the classic studies on nematode infections tfor instance, treatment. Cort, Otto and Spindler 1930: Otto, Cort and Keller 1931: Otto and Spindler 1930; and Winfield 1937) suggest that, among households of similar socioeconomic status, the contamination ofthe yard by the Literature Cited feces of young children is associated with increased Ascarts prevalence and intensity in the family (see chapter 23). Balasegaram, M. and Burkint. D. P. ( 1976). Stool 8. See chapter 7. characteristics and Western diseases. Lancer, 1, 152. ELEMENTS AND HEALTH RISKS 21 Bennett, E. R., Linstedt, K. D. and Felton, J. T. (1974). Rural Amnerican Journal oj Clinical Altirition, 29, 1480-1484. home wastewater characteristics. In / '. ., of the Gray, H. and Tainter. M. L. (1941). Colloid laxatives National Home Sewage Disposal Symposimi, Chicago, Dec. available for clinical use, American Journal oj'Digestive 9-10, 1974, pp. 74-78. St. Joseph, Mich.: American Society Diseases, 8, 130-139. of Agricultural Engineers. Greenberg, C. J. (1976). Studies on the Fibre in Human Diets. Burkitt, D. P., Walker, A. R. P. and Painter, N. S. (1972). Ph.D. dissertation. Cambridge: University of Cambridge. Effect of dietary fibre on stools and transit-times, and its Hindhaugh, G. M. A. (1973). Nightsoil treatment. The role in the causation of disease. Lzancet, 2, 1408-1412. Consiulting Engineer, 37, 47 and 49. (1974). Dietary fiber and disease. Journal ot the Hoogstraal, H., Meegan, J. M. and Khalil, G. M. (1979). The American Medical Association, 229, 1068-1074. Rift Valley fever epizootic in Egypt. 1977-78: ecological Connell, A. M. and Smith, C. L. (1974). The effect of dietary and entomological studies. Transactionzs oJ the Royal fibre on transit times. In Proceedings of' the Fourth Society of Tropical Medicine and Hygiene, 73, 624-629. International Symposium on Gastrointestinal Motility, Huponu-Wusu, 0. 0. and Daniel, S. 0. (1977). Public health Banif, Alberta, 1973; eds. Daniel, E. E. and others, pp. aspects of housing in Nigeria: observations on the human 365-368. Vancouver: Mitchell Press. factors in refuse disposal in Lagos. Health and Hygiene, 1, Cort, W. W., Otto, G. F. and Spindler, L. A. (1930). 153-158. Investigations on Ascaris lumbricoides and the associated Hypes, W. D. (1974). Characterization of typical household intestinal helminths of man in southwestern Virginia. gray water. In Man nal of'Gray Water Treartment Practice, Anmerican Journal of Hygiene, 11, 1-55. ed. Winneberger, J. H. T., pp. 79-88. Ann Arbor, Mich.: Cranston, D. and Burkitt, D. P. (t975). Diet, bowel Ann Arbor Scicncc Publishers. behaviour and disease. Lancet, 2, 37. International Agency for Research on Cancer, Instestinal Crofts, T. J. (1975). Bowel-transit times and diet. Lancet, 1, Microecology Group (1977). Dietary fibre, transit time, 801. faecal bacteria, steroids, and colon cancer in two Crowther, J. S., Drasar, B. S., Hill, M. J., MacLennan, R., Scandinavian populations. Lancet, 2, 207-211. Magnin, D., Peach, S. andTeoh-Chan, C. H. (1976). Faecal Kalbermatten, J. M., Julius, D. S., Gunnerson, C. G. and steroids and bacteria and large bowel cancer in Hong Mara, D. D. (1982). Appropriate Sanzitation Alternatives: A Hong by socio-economic groups. British Journal of Planning and Design Manual. World Bank Studies in Cancer, 34, 191-198. Water Supply and Sanitation 2. Baltimore, Md.: Johns Drasar, B. S. (1974). Some factors associated with Hopkins University Press. geographical variations in the intestinal microflora. In Laak, R. (1974). Relative pollution strength of undiluted Nomnal Microbiological Flora of'Man, Society for Applied waste materials discharged in households and the dilution Bacteriology Symposium no. 3; eds. Skinner, F. A. and waters used for each. In Manual of'Grey Water Treatinent Carr, J. G., pp. 187-196. London: Academic Press. Practice, ed. Winneberger, J. H. T., pp. 68-78. Ann Arbor, Evison, L. M. and James, A. (1977). Microbiological criteria Mich.: Ann Arbor Science Publishers. for tropical water quality. In Water, Wastes and Health in McGarry, M. G. and Stainforth, J. (1978). Co0npost, Hot Clim71ates; eds. Feachem, R. G. A., McGarry, M. G. and Fertilizer, adl Biogas ProduLctionfrom Humnan and Farm Mara, D. D., pp. 30-51. London: John Wiley. Wastes in the People's Republic of China. Ottawa: Feachem, R. G. A. (1977). Environmental health engineering International Development Research Centre. as human ecology: an example from New Guinea. In Mata, L. J., Carrillo, C. and Villatoro, E. (1969). Fecal Subsistence and Survival-Rural Ecology in the Pacific, eds. microflora in healthy persons in a preindustrial region. Bayliss Smith, T. and Feachem, R. G. A., pp. 129-182. Applied Microbiology, 17, 596-602. London: Academic Press. Otto. G. F., Cort, W. W. and Keller, A. E. (1931). Feachem, R.,G. A., Burns, E., Cairncross, A., Cronin, A., Environmental studies of families in Tennessee infested Cross, P., Curtis, D., Khalid Khan, M., Lamb, D. and with Ascaris. Trichuris and hookworm. American Journal Southall, H. (1978). Water, Healthz and Development: An of Hygiene, 14, 156-193. Interdisciplinary Evaluation. London: Tri-Med Books. Otto, G. F. and Spindler, L. A. (1930). Effect of partial Fuchs, H.-M., Dorfman, S. and Floch, M. H. (1976). The sanitation on infestation with intestinal parasites in effect of dietary fiber supplementation in man. II. southwest Virginia. Southern Medical Journal, 23, Alteration in fecal physiology and bacterial flora. 556-560. American Journal oj Clinical Nuttritionz, 29, 1443-1447. Pescod, M. B. (1971). Wastewater solids utilization and Goldsmith, H. S. and Burkitt, D. P. (1975). Stool disposal in tropical developing countries. In W"ater Supply characteristics of black and white Americans. Lancet, 2, and Wastewater Disposal in Developing Cotuntries: 407. Proceedings of a Water Slupply and Sanitation Seminar. Gotaas, H. B. (1956). Compostinig: Sanitary Disposal anid Bangkok, January 19-23, 1970, eds. Pescod, M. B. and Reclamation of' Organic Wastes. Monograph Series 31. Okun, D. A., pp. 208-226. Bangkok: Asian Institute of Geneva: World Health Organization. Technology. Goy, J. A. E., Eastwood, M. A., Mitchell, W. D., Britchard, J. Pradt, L. A. (1971). Some recent developments in nightsoil L. and Smith, A. N. ( ! r., Fecal characteristics contrasted treatment. Wl'ater Research, 5, 507-521. in the irritable bowel syndrome and diverticular disease, Small Scale Waste Management Project (1978 ). Management 22 HEALTH HAZARDS OF EXCRETA oJ Small Waste Flows. Report EPA-600/2-78-173. diseases in North China. III. Family environmental factors Cincinnati, Ohio: US Environmental Protection Agency. affecting the spread of Ascaris lumbricoides in a rural Southgate, B. A. (1979). Bancroftian filariasis in Egypt. population. Chinese Medical Journal, 51, 643-658. Tropical Diseases Bulletin, 76, 1045-1068. Winneberger, J. H. T. (1974). Manual oJ Gray Water Treat- Tandon, R. K. and Tandon, B. N. (1975). Stool weights in ment Practice. Ann Arbor, Mich.: Ann Arbor Science North Indians. Lancet, 2, 560-561. Publishers. Walker, A. R. P. (1975). Effect of high crude fiber intake on Witt, M., Siegrist, R. and Boyle, W. C. (1974). Rural transit time and the absorption of nutrients in South household wastewater characteristics. In Proceedings of African Negro schoolchildren. American Journal of the National Home Sewage Disposal Symposium, Chicago, Clinical Nutrition, 28, 1161-1169. December 9-10, 1974, pp. 79-88. St. Joseph, Mich.: White, A. U. (1977). Patterns of domestic water use in low- American Society of Agricultural Engineers. income communities. In Water, Wastes and Health in Hot WHO (1970). Sewerage Planning in the Greater Taipei Area: Climates, eds. Feachem, R. G. A., McGarry, M. G. and A Master Plan Report, Report no. Mara, D. D., pp. 96-112. London: John Wiley. WHO/UNDP/SF/CHA-27. Geneva: World Health White, G. F., Bradley, D. J. and White, A. U. (1972). Drawers Organization. of Water: Domestic Water Use in East Africa. Chicago: (1979). Human Viruses in Water, Wastewater and Soil. University of Chicago Press. Technical Report Series no. 639. Geneva: World Health Winfield, G. F. (1937). Studies on the control of faecal-borne Organization. 2 Environmental Classification of Excreta-related Infections VARIOUS DISEASES are related to excreta, and the environment, and the infective dose for humans-and engineer, administrator, and community development these and other key concepts are discussed before the worker cannot consider each disease separately in environmental classification is set forth. selecting improved excreta disposal technologies. Rather, a conceptual framework that links various kinds of excreta-related infections to the design and Understanding Excreta-Related implementation of particular disposal or reuse Infections technologies is required. Yet a biological classification grouping the excreted viruses, bacteria, protozoa, and Excreta may be related to human disease in two helminths may be less helpful to understanding the ways (figure 2-1). The agents of many important health aspects of alternative approaches to excreta infections escape in the body's excreta eventually to disposal than a classification of infections based upon reach others-the first means of relation-and these transmission routes and life cycles. Such a classification are "excreted infections." In some cases the reservoir of would be an "environmental" one. In fact, the infections escape in the body's excreta eventually to resemblance between a biological and an en- Because such infections cannot be controlled through vironmental classification is much closer in the case of changes in human excreta disposal practices, this study the excreta-related infections than in the case of the does not examine them. (A number of infections for water-related infections (see Bradley 1977). which both man and other animals serve as a reservoir, The purpose of an environmental classification is to however, have been included.) group infections in such a way that the efficacy of The second way in which excreta relate to human different preventive measures is made clear. An disease is through the insect breeding that waste environmental classification for the water-related disposal often encourages. Insects may be a nuisance in infections has already been proposed (Bradley 1977; themselves (as are flies, cockroaches, mosquitoes), but Feachem, McGarry and Mara 1977); the object here is they may also mechanically transmit excreted pa- to propose an environmental classification for the thogens either on their bodies or in their intestinal infections associated with excreta. The devising of such tracts (as do cockroaches and flies), and sometimes a classification encounters two major limitations. The first is that remarkably little is known precisely about (a) Infected excreta the transmission of several of these infections and the numbers of microbes needed to pass on the infections New infections to susceptible people. The second is that the bulk of the excreted viruses, bacteria, and protozoa differ quanti- (b) Excreta - Vector breeding/ tatively rather than qualitatively in their transmission Figure2-1. Thelinksbetweenexcretaandinjkction.In characteristics, making it easy to end up with a large, (a), the excreta themselves contain the pathogens which relatively uninformative category containing the may be transmitted by various routes to a new host. In majority of infections. Understanding these infections (b), the excreta (or sewage) permits the breeding of depends on some basic facts of transmission- certain flies and mosquitoes that may act as vectors of especially latency, persistence of pathogens in the excreted and other pathogens 23 24 HEALTH HAZARDS OF EXCRETA they may be vectors for pathogens that circulate in the blood (as are mosquitoes). The capacity of flies or Excreted load Lrtency Excreted loadPersistence -*-Infective dose cockroaches to serve as mechanical vehicles for lictlon excreted pathogens represents one of the many ways in which excreted disease agents are transmitted from anus to mouth. Careful disposal of human wastes, Figure 2i2 Fctors un1 'r the transmissio n of a precautions in food storage and handling, and controlfectiLe dose measures directed against flies and cockroaches would minimize the threat to health of these pests. The blood- feeding nature of the mosquito, however, poses a more Ex-creted load complex problem. The mosquito ingests agents of the diseases it transmits through biting already infected The concentration of pathogens passed by an persons and perpetuates the cycle of infection to new infected person, or excreted load, varies widely. A hosts by the same means. The pathogens it carries are person infected by a small number of nematode worms, therefore nonexcreted, and the concepts discussed in for instance, may pass only a few eggs per gram of feces, this chapter have little relevance; the important factors whereas a cholera carrier may excrete 106 vibrios per are those which determine the breeding habits of those gram, and a patient with an acute attack of cholera particular mosquito vectors that breed in sewage or may pass 1013 vibrios in a day. In areas where large sullage.' numbers of pathogenic organisms are being passed in The distinction between the state of being infected the feces, high pathogen concentrations in sewage are and the state of being ill must be kept in mind in common (see table 1-10). Even in a developed, considering the transmission of excreted infections. temperate country such as England, where water use is The most important segment of the population relatively high and salmonellosis relatively rare, raw involved in transmitting an infection frequently shows sewage may contain 104 salmonellae per liter. At these few or no signs of disease; conversely, individuals in concentrations a removal efficiency of 99 percent in advanced states of disease may be of little or no sewage works will still leave 102 pathogenic organisms importance in transmission. Schistosomiasis is a good per liter of effluent. The health implications of these example: as much as 80 percent of the total egg output in pathogens will depend upon the effluent disposal feces and urine reaching water from a human method, the pathogens' ability to survive or multiply. population may be produced by children 5 to 15 years and the infective dose required. old, many of whom will show minimal signs of disease. Conversely, middle-aged people in terminal stages of schistosomiasis may produce few or no viable LatencY schistosome eggs. If an excreted infection is to spread, an infective dose Latency is the interval between the excretion of a of the disease agent has to pass from the excreta of a pathogen and its becoming infective to a new host. patient, carrier, or reservoir of the infection to the Some organisms-including all excreted viruses, mouth or some other entryway of a susceptible person. bacteria, and protozoa-have no latent period and are Spread will depend upon the numbers of pathogens immediately infectious in raw excreta. The require- excreted, upon how these numbers change during the ments for the safe disposal of excreta containing these particular transmission route or life cycle, and upon agents are different from those for helminthic infections the dose required to infect a new individual. Infective which have prolonged latent periods. Latency can dose is in turn related to the susceptibility of the new affect the choice of disposal systems: infections that host. Three key factors intervene to govern the have a considerable latent period are largely risk free in probability that, for a given transmission route, the carted night soil, whereas the others constitute a major numbers of excreted pathogens (excreted load) from health hazard in fresh night soil. In the environmental one host will form an infective dose for another: classification that follows, therefore, the first two latency, persistence, and multiplication. These concepts categories, in which no latency is observed, are will be discussed in turn; their relation is expressed in separated from the remaining categories, in which a figure 2-2. definite latent period occurs. 1. See category \i in the next main section of this chapter. The Among the helminthic infections (see table 1-9), only relation of insects to excreta and disease is examined in detail in three have eggs or larvae that may be immediately chapters 36 and 37. infectious to man after being passed in the feces. These ENVIRONMENTAL CLASSIFICATION OF INFECTIONS 25 are the pinworm (Enterobius vermicularis), a dwarf bacterial infections. This may determine the usual tapeworm (Hylnenolepis uiana), and occasionally a mode of infection, since multiplication in water is rare minute nematode ( -i. 1. stercoralis). All the and limited compared with the massive increases other excreted helminths require a distinct latent possible in food. Excreted viruses and protozoa do not period, either because their eggs must develop into an multiply outside their animal hosts. infectious stage in the environment outside the body, or Among the helminths transmitted by excreta, all the because these parasites have one or more intermediate trematodes infecting man undergo multiplication in hosts through which they must pass in order to complete aquatic snails. This aquatic stage in their life cycles their life cycles. introduces a prolonged latent period of a month or more while the trematodes develop in the snail, Persistenice followed by an output to the environment of up to several thousand larvae for each egg reaching the Viability of the pathogen in the environment, or water. (Category v of the environmental classification persistence, is a measure of how quickly it dies after below contains infections of this sort.) leaving the human body. This single property is the most indicative of the fecal hazard: a highly persistent Infective dose pathogen will create a risk throughout most treatment processes and during the reuse of excreta. In a predictable world the assessment of health risk A pathogen with short persistence outside the body, could simply be calculated from the output of however, must rapidly find a new, susceptible host. pathogens in the excreta of those infected, the median Transmission, therefore, cannot follow a long route infective dose (ID,O) of particular organisms, and the through sewage works and the final effluent disposal efficiency of excreta treatment processes in inactivating site back to man, but will rather involve the family or pathogens. Because of the variable infective dose of other close group, within which infection is transferred most pathogens and the uneven distribution of from one person to another through lax personal infection in the environment, the real world is much cleanliness. More persistent organisms, in contrast, can less calculable than this. Although the minimal readily generate new cases of disease much farther infective dose for some diseases may be a single afield. As persistence increases, so then must concern organism, or very few, the doses required in most for the ultimate means of excreta disposal. Similarly, bacterial infections are much higher. Data on infective pathogens that tend to persist in the general doses are very hard to acquire, since they involve environment will require more elaborate processes to administering a known dose of a pathogen to a human inactivate them in a sewage works. Methods of volunteer. Information is scanty and concerned with sequestering these pathogens, such as sedimentation doses required to infect half those exposed (ID50), into a sludge for special treatment, are often needed. rather than a small proportion, at a single exposure. Measurement of pathogen persistence in a labo- The volunteers generally have been well-nourished ratory is easy. Laboratory results, however, need adults usually from non-endemic areas. Results of this confirmation by field studies which are more difficult. kind must therefore be applied with great caution to Interpreting field results on persistence requires malnourished peasant children continually exposed to knowledge of how many pathogens are being shed in a an infection. It has been found that changes in the community's excreta (relatively easy to determine) and manner of administering experimental doses, such as the infective doses for man (extremely difficult). preceding a dose of cholera vibrios with an alkaline substance to reduce temporarily free gastric acid. may Multiplication lower the tD50 of such organisms by a factor of 103 (Hornick and others 1971). And, although ID50 may be Under favorable conditions certain pathogens will the most reliable gauge of infectivity in human multiply in the environment. Originally low numbers experimental studies, in natural transmission the can thus produce a potentially infective dose (see the infective dose for 5 percent or less of the population next section). Bacteria may multiply on a favored may be of greater epidemiological significance. substrate (for instance, Salmonella on food) and Uncertainty over the size of the minimal infective trematode worms multiply in their molluscan in- dose in nature makes it a difficult criterion to use in termediate hosts. In the former case, light fecal devising a classification; nevertheless, it is too contamination may increase bacterial numbers to the important to be left out. The difficulties are greatest high minimal infective doses required in many excreted with the major excreted bacterial infections and with 26 HEALTH HAZARDS OF EXCRETA protozoa. For excreted viruses there is evidence of low and disease is limited to a few of the youngest children, ID,0s in the laboratory, and in human populations who may suffer chronic paralysis. If sanitation is (World Health Organization 1979). In helminthic improved, infection is deferred to later in life, when its infections a single egg or larva can infect if ingested, pathological consequences are more serious. Thus, even though a high proportion of worms can fail to although poliovirus transmission may be reduced by mature (especially in locations where immunity is improving sanitation, improvements will not neces- present). sarily curtail the disease, a result achieved in practice by immunization. This pattern may also apply to other excreted infections such as infectious hepatitis, and it Host response has been proposed for typhoid. There are several other Host response is important in determining the effect excreted infections, however, in which human im- once an individual has received a given dose of an munity is of importance in regulating the amount of infectious agent. Acquired immunity, and the relation disease. Immunity tends to diminish the health of age to pathology, are particularly important in significance of moderate sanitary improvements, and predicting the effects of sanitation. At one extreme may in part explain the disappointing effects of some would be infection with a short-lived parasite to which sanitary programs (table 2-1).2 little immunity develops and for which the relation In other words, the balance between exposure to between infection and disease is not age dependent. A infection and host response to it will determine the close, almost linear relationship between exposure and pattern of the excreta-related disease. If transmission, disease might be expected in this case, with appropriate creating exposure to a particular infection, is limited, improvements in sanitation yielding health benefits then most people will not have encountered the proportional to effect. Ascaris closely approximates infection and will be susceptible. If a sudden increase in this model. transmission of the disease occurs, it will affect all age At the other extreme would be infection with viruses groups in the form of an epidemic. Under these or bacteria to which long-lasting immunity develops circumstances improvements in sanitation that strike and for which the chance of overt, symptomatic disease at pathogen transmission will have a considerable in those infected rises with increasing age. An example of this case is infection with poliovirus (see table 1-5). Under poor sanitary conditions all persons are infected 2. See also chapter 3 for a detailed discussion of the health benefits at a young age, older children and adults are immune, from improvements in sanitation. Table 2-1. Summary of selected literature on the effect on health of imnprovled excreta disposal Country and type of study Finding Source Brazil In a village of 1,041 inhabitants, a socioeconomic From 1961 to 1968, Schistosoma mansoni Barbosa, Pinto and Souza and schistosomiasis survey in 1961 was prevalence rates fell from 7 to 0 percent among (1971) followed by introduction of schistosome control 0-4 year olds, from 27 to 4 percent among 5-9 measures, including latrines, water supplies, year olds and from 56 to 9 percent among laundry facilities, showers and health education. 10-14 year olds. The prevalence of S. mansoni Fecal surveys were carried out in 1961, 1966, infection in domestic rodents and snails also fell 1967 and 1968. Other villages without these considerably. The cost of the control measures interventions were surveyed in 1963 and 1969. was US$0.98 per month per protected person over 7 years. Colombia 15 municipal primary schools in a poor suburb of Diarrhea and vomiting were more common Koopman (1978) Cali were visited and 8,444 schoolchildren were among children in schools with lower hygienic interviewed. The school's toilet facilities were scores. The individual factors most associated inspected and the children were asked if they with diarrhea prevalence were feces in the toilet had had diarrhea, vomiting, colds or headlice bowl, and an absence of toilet paper, towels, over the past week. The observations of toilet soap or taps for hand washing. Hygienic scores facilities were used to compute a "hygienic were not related to colds or headlice, and score" for each school. classroom crowding was weakly related to vomiting, colds and headlice. ENVIRONMENTAL CLASSIFICATION OF INFECTIONS 27 Table 2-1 (continued) Country and type of study Finding Source Costa Rica Diarrheal morbidity, intestinal bacteria, parasites, Ascaris prevalence decreased as the type of Moore, de la Cruz and Vargas- quality of water, meat and milk and the fly excreta disposal improved. Trichuris prevalence Mendez (1965) population were surveyed among 1,202 houses. was the same among individuals with or Three types of excreta disposal facility were without a latrine but was lower among distinguished: none (12 percent of houses), pit individuals having a septic tank. Shigella latrine (76 percent of houses) and flush toilets organisms were not recovered where a septic with septic tanks (12 per cent of houses). tank was present. Diarrhea morbidity was least amongst those living in houses with no latrine. Excreta disposal facility was not associated with protozoal prevalence. An outbreak of 167 cases of infectious hepatitis Infectious hepatitis cases occurred in 1.6 percent Villarejos and others (1966) was investigated between December 1963, and of houses with a flush toilet, 2.7 percent of July 1964. The outbreak occurred during a houses with an outdoor latrine and 2.6 percent severe drought. Person-to-person contact was of houses with no facility. considered the likely mode of spread. Egypt Surveys were made in 1952 of helminthic and Protozoal prevalence rates and the mean number Chandler (1953 and 1954) protozoal infections in two neighboring of protozoal infections per person were not villages: A and B. Village A had been surveyed reduced in Village A. Ascaris and hookworm in 1950. Village A had improved water supply, prevalence rates and intensities were reduced. a borehole latrine in 90 percent of houses, a refuse collection service and visiting nurses. Village B was untouched. Prisoners used bucket latrines and treated Nile Schistosomiasis and hookworm prevalences in the Khalil (1931) water. Nearby villagers had no latrines and local population were approximately 75 percent used untreated Nile water. Parasite infections and 70-88 percent respectively. Among of the villagers were compared with those of prisoners, the rates fell from 30 percent and 68 the prisoners after various periods of percent respectively to less than 20 percent in incarceration. both cases after 5 years of incarceration and to about 10 percent after 12 years. Reinfection with Ascaris occurred regularly owing to contamination of sewage-irrigated vegetables. Various combinations of latrines and drug Latrines had no impact on Ascaris, hookworm or Scott and Barlow (1938) therapy were investigated in villages for 6 years schistosome infections. from 1928. Various combinations of water supply, latrines, The installation of water supply and latrines did Weir and others (1952) refuse disposal, fly control and therapy were not alter the infant mortality or crude death investigated in 5 villages during 1948-51. rates and did not change the fly status in any of the villages. Guatemala Acute diarrheal rates among families having a In those families having a latrine, diarrheal rates Gordon and others (1964) latrine were compared with rates amongst were somewhat lower for those over 2 years those with no latrine. old, but not for those under 2. Two lowland villages were studied during The results of this study have not yet (mid-1981) Schneider, Shiffman and 1973-76. In-house water supply and sanitary been fully published. Preliminary reports Faigenblum (1978); Shiffman education were implemented in one village; the indicate that malabsorption was somewhat and others (1979) other village provided a control. lower in the intervention than the control village, that there were no differences in overall diarrhea incidence but that there was less diarrhea among 2-7 year olds in the intervention than the control village. 28 HEALTH HAZARDS OF EXCRETA Table 2-1 (continuied) CountrY and type of study Finding Source 'itzdti The impact of a bored-hole pit latrine and health The authors state that the invervention was Kumar. Sehgal and Singh (19701 education program on the incidence of diarrhea related to "a declining trend in diarrhoeal in children in the village of Bharwara, near morbidity", but the data presented do not Lucknow, was investigated. support this. A single stool examination on 13.267 hospital The prevalence of Eniroinoehu histolytica excretion Mathur and Kaur (19721 patients and their contacts was carried out at among those living in homes with no latrines Karnal. Haryana State. A sanitary inspector (38.3 percent) was a little higher than for those was sent to the homes of the patients to collect using latrines j31.6 percent) (p<.01). The information on hygiene and domestic facilities. authors point out that this difference cannot necessarily be attributed to the latrines. Iran Impact of mass treatment, sanitation and Mass treatment was highly effective tn reducing Arfaa and others (19771 sanitation plus mass treatment on soil- both the prevalence and intensity of transmitted helminths was studied in 15 villages Aclcylostonia and Ascaris. Sanitation, added to in southwest Iran. Sanitation was one pit mass treatment, contributed nothing. Sanitation latrine per family and a communal water atone had an impact upon the intensity of both supply. hookworm and roundworm and had a little impact on the prevalence of roundworm only. Ascariasis was studied in a village of 850 people The prevalence of infection fell from 67 percent to Sabba and Arfaa 11967) in southwest Iran before and after the 57 percent over the study period (February construction of a water supply, a public bath- 1963 to December 1965J. Mean egg output fell house, a laundry and 114 pit latrines (nearly from around 11 per milligram of feces to 4. The one for every household). pit latrines cost US$0.5 per capita and were the major cause of the reduced ascariasis. Japan A program of heat treating (with firev-ood) of The prevalence of hookworm and A.scori.s Katayama (19551 night soil (up to 601C) prior to agricultural declined "strikingly" in the intervention village application was implemented in a village in and there was a marked decrease in the count Shiga Prefecture. A control village was left of Ascaris eggs found in the soil. These changes untouched. were not observed in the control village. Heat treating of night soil (with surplus night Night soil treatment alone had only a slight effect Kawagoe and others (195S) electricity) was implemented in a village near on the prevalence of parasite infections. When Osaka city. mass chemotherapy was carried out. prevalences fell markedly (hook"orm from 52 percent to 11 percent, Ascaris from 33 percent to 12 percent) and remained at this low level throughout the 5 month observation period. Night soil treatment with thiabendazole was The prevalence of ascariasis fell by 50 percent in Kutsumi 11969) implemented in a village of 5,000 people near Area A, by 30 percent in Area B and hardly at Tokyo. Three areas were distinguished: Area A, all in Area C. The rate of new infections with night soil treatment + chemotherapy: Area B. Tricltris was one-third. and that of hookworm night soil treatment only; Area C. was one-half in Area A compared with Area C. chemotherapy only. Parasite prevalence was surveyed between July 1964 and March 1966. Alucufritius Diarrheal rates in households with differing Compared with families with an indoor toilet, van Zijl (1966) sanitation facilities were studied in 1960, families with an outdoor toilet had 4 times the diarrhea incidence and families with no toilet had 10 times the diarrhea incidence. Pauoi lest A series of egg counts were made in two villages. Reinfection after mass treatment was rapid, but Cort, Schapiro and Stoll (1929) one partially sanitated and the other entirely reinfection with hookworm was delayed in without latrines, before and after mass those groups with more and better maintained chemotherapy. latrines. ENVIRONMENTAL CLASSIFICATION OF INFECTIONS 29 Table 2-1 (continued) Country and type of study Finding Source Panama (cont.) Children presenting at a clinic in Panama City The three pathogens were absent from children Kourany and Vasquez (1969) were examined for excretion of coming from the best housing type, whereas for enteropathogenic Escherichia coli. Shigella and other housing types, about 8 percent of Salmonella. These data were related to children had one or more of the pathogens in information about type of housing and sanitary their feces. facilities. Surveys were conducted over 7 years into In villages without latrines, the prevalence and Sweet and others (1929) environmental conditions and helminthiases. intensity of hookworm rose to, or above, original levels within 3 or 4 years after a mass drug campaign. In villages with latrines, prevalence and intensity also rose again following drug treatment but a degree of protection against reinfection was observed among women. Philippines A region with endemic cholera was divided into 4 The apparent reductions in cholera incidence Azurin and Alvero (1974) areas: Area A, control area having poor water were 73 percent in Area B, 68 percent in Area and sanitation facilities; Area B, improved C and 76 percent in Area D. water supply; Area C, pour-flush pit latrines; Area D, improved water supply and communal latrines. Singapore 159 families living in modern flats and 169 Ascaris, hookworm and Trichuris prevalence rates Kleevens (1966) families living in squatter housing were studied. were 9, 1 and 28 percent, respectively, among The people in the flats had previously lived in flat dwellers and 63, 2 and 58 percent among the squatter housing but had been rehoused squatters. The high Trichuris prevalence among following a fire in 1961. Average family income flat dwellers was attributed to the longevity of of flat dwellers was S$165 per month whereas this worm. for squatters it was SS130 per month. Stool samples were collected from all children under 13 years old in the selected households. St. Lucia A longitudinal study of 229 children in three Children in the valley with improved water and Henry (1981) valleys. Weights and heights were recorded the valley with improved water and latrines had monthly; stools were examined for worm eggs less ascariasis. trichuriasis and diarrhea, and every 6 months, and parents kept diarrhea grew better, than children in the valley with no diaries for their children. The children were 0-6 improvements. months old at the start of the study and were followed for 2 years. Sudan Diarrhea incidence in households with differing In one particular month, families having a van Zijl (1966) sanitary facilities were studied in 1961. communal unsanitary privy experienced a higher diarrheal morbidity rate than similar families having no toilet. Union ol Soniet Socialist Republics A village of 1,600 people was studied before and Before the intervention, the prevalence of Ascasis Rosenberg (19601 after the abolition of untreated night soil as a eggs was 100 percent in soil samples and 71 fertilizer and a campaign of "improving general percent in fruit samples. 41 percent of soil eggs hygiene." and 19 percent of fruit eggs were viable. After the intervention, 35 percent of soil samples and 25 percent of fruit samples contained eggs. No eggs were viable. 30 HEALTH HAZARDS OF EXCRETA Table 2-1 (continued) Country and type of study Finding Source United States 400 patients at a veterans' hospital in Georgia The overall prevalence of infection with Brooke, Donaldson and Brown had stool examinations for intestinal protozoa Entamoeba histolytica was 9.3 percent. Among (1954) and helminths, and completed questionnaires those not infected, 22 percent had outside on their military service and living conditions. toilets, whereas among those infected, 55 percent had outside toilets (p <.01). Income was not significantly associated with Ent. histolytica infection. A survey of 357 people in 4 areas near Little The overall prevalence of infection with one or Brooke and others (1963) Rock, Arkansas, was carried out in 1961. Stools more protozoon (APR) was 33 percent. Among were examined for intestinal protozoa. all individuals served with piped indoor water supply the APR was 31 percent, whereas among those using well water it was 35 percent (no significant difference). However, among 0-4 year old piped water users the APR was 13 percent, whereas among 0-4 year old well- water users it was 37 percent (p<.05). Many of the houses with piped water also had sewerage, whereas well-water houses had septic tanks or outside pit latrines. 2,657 people living in a rural area of West Entamoeba histolytica and Ascaris prevalence Eyles, Jones and Smith (1953) Tennessee were surveyed for intestinal parasites. rates were 19 and 8 percent, respectively, 90 percent were black. Details of family size, among those with clean latrines, 36 and 11 cleanliness, housing, water supply and excreta percent among those with dirty latrines, and 29 disposal were also collected. and 15 percent among those with no latrines. Parasite prevalence was also found to be associated with family size, fecal contamination of the premises, cleanliness of house and person but not with water pollution. A survey of shigellosis among children under 10 The prevalence rates of Shigella excretion were 1.6 Hollister and others (1955) years old in farm labor camps in California was percent in cabins with inside water, shower and conducted. toilet, 3.0 percent in cabins with inside water but shared shower and toilet facilities, and 5.8 percent in cabins with all services shared. White females (age 18-76 years) at a mental The percentage of people infected with Ent. Jeffery (1960) institution in California were studied during histolytica and Giardia lamblia rose steadily 1954-57. They were originally housed in an old during the survey, indicating that transmission building in which standards of sanitation were was continuing throughout the period. poor. They were then rehoused in a new, However, although the percentage of people modern hospital building with excellent infected with hookworm (73 percent) and sanitary facilities. Stool examinations were Trichuris (83 percent) remained constant, as made on 110 patients prior to rehousing and would be expected in the absence of mass on 8 subsequent occasions. chemotherapy, no new cases of hookworm and only 3 new cases of Trichuris were reported while the patients were in the new building. Thus, the move to the new building interrupted the transmission of the helminths but not the protozoa. ln 1952 a program of borehole latrines was The latrine program was associated with a McCabe and Haines (1957) implemcnrted in Boston, Georgia. The reduction in the detection of Shigella from prevalence of Shigella excretion, in Boston and rectal swabs from 4.7 percent to 2.8 percent. control towns, was surveyed in children under Rates in control towns did not fall over this 10 years old. period. ENVIRONMENTAL CLASSIFICATION OF INFECTIONS 31 Table 2-1 (continued) Country and type of study Finding Source United States (cont.) Excretion of Entamoeba histolytica among 1,115 Ent. histolytica prevalence rates were 6 percent for Mackie and others (1956) urban school children in North Carolina was those with an inside flush toilet, 12 percent for studied. These data were related to excreta those with a shared flush toilet and 58 percent disposal, water supply and garbage disposal for those with a pit latrine. Infection with Ent. facilities in the homes of the children. histolytica was also associated with type of water supply and garbage disposal facilities. Hookworm and Ascaris surveys were conducted The introduction of pit privies in the Otto and Spindler (1930) in Virginia. mountainous areas of Virginia was effective in reducing the hookworm prevalence, but not Ascaris. Environmental studies were made of 329 families Ascaris and Trichuris infections were confined Otto, Cort and Keller (1931) in the mountain region of Tennessee and 202 largely to the mountain areas. Yard pollution. families living in the central basin, western and with it heavy Ascaris infection, were plains and lowlands of the state. present regardless of the presence or absence of latrines. Studies were conducted in 11 mining camps in Shigella and Ascaris prevalence rates were 1.1 and Schliessmann and others (1958) eastern Kentucky from 1954 to 1957. Reported 7 percent, respectively, among those with water diarrheal disease rates, Shigella isolations from and flush toilet inside, 2.4 and 25 percent rectal swabs of pre-school children and parasite among those with water inside and latrine prevalence were investigated. outside, and 5.9 and 42 percent among those with water and latrine outside. Shigella infection data from 28,000 rectal swabs The rates of new Shigella infections occurring Stewart and others (1955) were analysed according to the type of housing. during the study period were: Housing was divided into 4 categories (poor, 6.2 percent among those in "poor" houses, fair, good, very good) according to water 2.2 percent among those in "fair" houses, supply, excreta disposal, fly population and 0.6 percent among those in "good" houses and esthetic and structural quality. 0.3 percent among those in "very good" houses. Note: The limitations of the literature on health benefits from sanitation and the difficulties in assessing these benefits are discussed in chapter 3. effect in reducing an epidemic's likelihood and its and of water supplies, and poliomyelitis, which can be magnitude if one occurs. prevented only by immunization. By contrast, if transmission is vigorous, most people The consequences of a disease's juvenile will be repeatedly exposed to an infection, having first prevalence-not only that children chiefly suffer, but acquired it in childhood. Subsequent exposures may be also that children are the main sources of infection- without effect if immunity is developed after the first presents a further challenge to sanitation. The acute attack, or immunity may develop cumulatively from a need for better community excreta disposal must focus series of attacks. The infection will nevertheless always on young children, the group perhaps least inclined to be present, and can be described as endemic. Under use any facilities that are made available. these conditions much of the transmission is ineffective because of human acquired immunity, and reduced transmission through improved sanitation will only Nonhuman hosts delay the occurrence of infection somewhat, so that older children exhibit symptoms. Extensive sanitary Some excreted infections (for example, shigellosis) improvements will either render the infection rare or, if are confined strictly to humans, and the control of the disease was originally highly transmitted, make it human excreta alone is required for their prevention. an adult disease. Diseases exemplifying this state of Many others (for example, salmonellosis) involve wild affairs are typhoid, which can be completely prevented or domestic vertebrate animals as well as man. Such an in a community by adequate management of excreta infection is called a zoonosis. 32 HEALTH HAZARDS OF EXCRETA Zoonoses infective dose, persistence, multiplication, and trans- mission. Further data on specific excreted pathogens- A,1n/ma/s arranged by category and epidemiological feature- g > Animal are provided in table 2-3.3 Control measures in parallel appropriate to each environmental category of pathogen are indicated in table 2-2, and data on immunity and pathogen concentrations in excreta, Aoimcs \which vary with each organism, are contained in table Animal 2-3. in There is a clear difference between the first five series categories of excreted pathogens and the last, which Man contains exereta-breeding insect vectors of disease, in Figure 2-3. Involvement of other vertebrates it? that the insects themselves are not pathogens and that a transmission oj human excreted inJections. Examples of variety of sanitation methods and additional specific zoonoses in parallel are salmonellosis and balan- measures can be directed against these vectors. For tidiasis; examples of zoonoses in series are beef and these reasons category vt Is not Included in table 2-3. pork tapeworm infections The excreted infections are divided on the basis of There are two groups of zoonoses, and each has the presence (categories in to v) or absence (categories quite different implications for sanitation (figure 23). and II) of a latent period (health problems associated In the first group, animals act as hosts alternative to with fresh feces or night soil occur primarily in these first two categories). The distinction between cate- man: even If human excreta IS under completely safe gre adI n aeoisH oVi udmna n control, the excreta of other animals can continue to gories i and II and categones iii to v IS fundamental and transmit the infection. In effect, the animal involved is clear-cut, correspondig closely to the biology f th 'in parallel" with man, and it is necessary to control pathogens (in that all infections in categories jn to v are both human and animal excreta. In the second group. helminthic). The subdivisions of the infections having latency are the animal is an essential step in the transmission of the disease from one human to another (figure 2-3, "in also clear, with category III containing the soil- series"). In this case control of either human excreta transmitted worms, Iv the tapeworms, which depend alone or the animal infection alone will suffice to end on the access of cattle and pigs to human feces, and v transmission. In the environmental classification the trematodes and other worms requiring aquatic below, this second group which contains the human intermediate hosts. The subdivision of categories I and tapeworm of. the genus Taenia,is therefore separated II, however, is difficult and somewhat arbitrary because tapeworm s of ther tgreus Thenia,is therefore separated the various concepts discussed above can arrange the from the other categories. ~infections of these categonies in different ways. If Some excreted helminthic infections have in- categories anddffarctgwy catgores an 11arcdivided, for instance, on thc basis vertebrate intermediate hosts (see table 1-9); they will ofies Ith th gre limitatinstof the bdata be controlled if excreta are prevented from reaching on iti doe kept inimind, the aprimate the intermediate hosts, or the intermediate hosts are on infective dose kept in mind, the approximate controlled, or if people do not eat the intermediate host ranking of pathogens (in order of increasing ID50) uncooked . do not. have contact with thewaterin shown in table 2-4 emerges. But if the infections are unicoohed ontermedoothe ontact withs thepen g wather listed in the order of increasing persistence outside whrtichlar thegintermediae hoste) l .(dependingonth their animal host, the approximate ranking shown in table 2-5 is appropriate. Another important factor in Categories of Excreta-related Infections predicting the effects of improved exereta disposal facilities is whether or not a significant nonhuman There are several ways in which the excreted reservoir of infection (see figure 2-3) exists for a infections can be grouped according to the epide- miological features discussed above, but a 3. Part Two of the book is devoted to detailed analyses of classification that considers the effects of excreta individual pathogens and diseases according to these and additional disposal and changes in disposal facilities and environmental factors. But it was thought that, for easier reference, technologies has been chosen, and is given in table 2-2. Part Two should group the pathogens by kind and not by the categories described in this chapter. Part Two is divided into section Six categories of infection have been distinguished In ............ L the excreted viruses; section II, the excreted bacteria, section III, the table, and the relevant environmental or epidemio- the excreted protozoa: section IV, the excreted helminths; and logical features broadly considered are latency, section V, the exereta-breeding insects and the diseases they transmit. ENVIRONMENTAL CLASSIFICATION OF INFECTIONS 33 Table 2-2. Environmental classification of excreted infections Category and Emnironmental Major control epidemiological ftatures3 Infection transmission Jbcus measure t. Non-latent; low Amebiasis Personal Domestic water supply infective dose Balantidiasis Domestic Health education Enterobiasis Improved housing Enteroviral infections' Provision of toilets Giardiasis Hymenolepiasis Infectious hepatitis Rotavirus infection n. Non-latent; medium or Campylobacrer infection Personal Domestic water supply high infective dose; Cholera Domestic Health education moderately persistent; Pathogenic Escherichia Water Improved housing able to multiply coli infection' Crop Provision of toilets Salmonellosis Treatment of excreta Shigellosis prior to discharge Typhoid or reuse Yersiniosis iii. Latent and persistent; Ascariasis Yard Provisions of toilets no intermediate host Hookworm infectiond Field Treatment of excreta Strongyloidiasis Crop prior to land Trichuriasis application iv. Latent and persistent: Taeniasis Yard Provision of toilets cow or pig as Field Treatment of excreta intermediate host Fodder prior to land application Cooking, meat inspection v. Latent and persistent; Clonorchiasis Water Provision of toilets aquatic intermediate Diphyllobothriasis Treatment of excreta host(s) Fascioliasis prior to discharge Fasciolopsiasis Control of animal Gastrodiscoidiasis reservoirs Heterophyiasis Control of intermediate Metagonimiasis hosts Opisthorchiasis Cooking of water plants Paragonimiasis and fish Schistosomiasis Reducing water contact iv. Spread by excreta-related Bancroftian filariasis Various fecally Identification and insects (transmitted by Culex contaminated sites elimination of pipiens) in which insects breed suitable insect All the infections in breeding sites i-v able to be transmitted mechanically by flies and cockroaches a. See table 2-3 for data on additional epidemiological features by pathogen. b. Includes polio-, echo-, and coxsackievirus infections. c. Includes enterotoxigenic, enteroinvasive, and enteropathogenic E. coli infections. d. Ancylostoma duodenale and Necator aonericanus. Table 2-3. Basic epideiniologicalifeatures oJ excreted pathogens by environmental category Median Mtiltiplication injective Major Excreted outside human dose Significant nonihuman Intermediate Pathogen load' Latenctb Persistencec host (ID50) immunity? reservoir? host CATEGORY I Enteroviruses' 107 0 3 months No L Yes No None Hepatitis A virus 106?) 0 ? No I(?) Yes No None Rotavirus 106(?) 0 ? No L(?) Yes No(?) None Balartidium coli ? 0 ? No L(?) No(?) Yes None Entamoeba hisiolytico l0o 0 25 days No L No(?) No None Giardia lamblia t05 0 25 days No L No(?) Yes None Enterobius vermiciilaris Not 0 7 days No L No No None usually found in feces Hymenolepis nana ? 0 1 month No L Yes(?) Not'?) None CATEGORY 11 Campylobacter fetus N ssp. jejuni l0o 0 7 days Yese H(?) ? Yes None Pathogenic a Escherichia coli' i0, 0 3 months Yes H Yes(?) No(?) None Salmonella m S. typhi ol 0 2 months Yesc H Yes No None Other salmonellae 108 0 3 months Yes' H No Yes None Shigella spp. 107 0 1 month Yes' M No No None i Vibrio cholerae 107 0 1 month(?) Yes H Ycs(?) No None Yersinia enterocolitica l05 0 3 months Yes H(?) No Yes None CATEGORY III Ascaris lumbricoides 104 10 days 1 year No L No No None Hookwormsg 102 7 days 3 months No L No No None Strongyloides stercoralis 10 3 days 3 weeks Yes L Yes No None (free-living stage much longer) 7richuris trichlira 103 20 days 9 months No L No No None CATEGORY IV Taenia sagilrata and 104 2 months 9 months No L No No Cow T solium1i (7: saginata) or pig (T soliun) CATEGORY V Clonorchis sinensis' 102 6 weeks Life of fish Yesi L No Yes Snail and fish Diphyllohothrium 104 2 months Life of fish No L No Yes Copepod and latumi fish Fasciola hepaticah ? 2 months 4 months Yesi L No Yes Snail and aquatic plant Fasciolopsis buskih 103 2 months ? Yes' L No Yes Snail and aquatic plant Gastrodiscoides homibish ? 2 months(?) 7 Yesi L No Yes Snail and aquatic plant Heterophyes heterophyes' ? 6 weeks Life of fish Yes' L No Yes Snail and z fish C Metagonimus 7 6 weeks(?) Life of fish Yesi L No Yes Snail and 0 yokogawai' fish Paragonimus ? 4 months Life of crab Yesi L No Yes Snail and westermani' crab or - crayfish r Schistosoma S. haematobium' 4 per 5 weeks 2 days Yesi L Yes No Snail ;> milliliter of - urine S. japonicumh 40 7 weeks 2 days Yesi L Yes Yes Snail H S. mansoni" 40 4 weeks 2 days Yesi L ? No Snail C S~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Leptospira spp. urine(?) 0 7 days No L Yes(?) Yes None L Low (106). ° ? Uncertain. a. Typical average number of organisms per gram of feces (except for Schistosoma haematobium and Leptospira, which occur in urine). b. Typical minimum time from excretion to infectivity. c. Estimated maximum life of infective stage at 20°-30°C. d. Includes polio-, echo-, and coxsackieviruses. e. Multiplication takes place predominantly on food. f. Includes enterotoxigenic, enteroinvasive, and enteropathogenic E. coli. g. Ancylostoma duodenale and Necator americaons. h. Latency is minimum time from excretion by man to potential reinfection of man. Persistence here refers to maximum survival time of final infective stage. Life cycle involves one intermediate host. i. Latency and persistence as for 'Taenia. Life cycle involves two intermediate hosts. j. Multiplication takes place in intermediate snail host. k. For the reasons given in chapter 1, Leptospira spp. do not fit any of the categories defined in table 2-2. 36 HEALTH HAZARDS OF EXCRETA Table 2-4. Category I and 11 pathogens Table 2-5. Category I and II pathogens (from table 2-2) (from table 2-2) rcanked by median infective ranked by persistence outside host diose (ID5s) Pathogen Persistence Balantidium coli Balantidium coli (?) Campylobacterfetus spp. jejuni ?) Entamoeba histoitrica Entamnoeba histolytica L Enterobius cermnicularis Enterobius rermicularis L Enterovirusesa Giardia lamblia Giardia lamblia L HyGiearolepis nana Hepatitis A virus (2/ Salmonella typhi Hymenolepis nana Shigella spp. M Rotavirus (?) Vibrio cholerae J Shigella M Enterovirusesa Campylobacterjetus ssp. jejuti /i) Pathogenic Eschiericliia coli' H Pathogenic Escherichia colib 1 Salmonellae Salmonella | Yersinia enterocolitica S. tvphi H Other salmonellae L Low (<1 month): M medium I month): H high (> I Vibrio cholerae I month). Yersinia enterocoiitica (?) J ? Uncertain. a. Includes polio-, echo-, and coxsackieviruses. L Low ( < 102; M medium t 104): H > 106). b. Includes enterotoxigenic, enteroinvasive, and enteropatho- ? Uncertain. genic E. coli. a. Includes poaio-, echo-, and coxsackieviruses. b. Includes enterotoxigenic. enteroinvasive, and enteropathogenic E. coli. Table 2-6. ID50 and persistence oj categorv I anid If pathogens (from table 2-2) commonly' and rarely particular pathogen; four of the pathogens in transmitted in European communities categories I and it (Campylobacter, salmonellae Balantidiuim coli and Giardia lamblia) have significant P"" ID50 Persistetnce animal reservoirs (table 2-3). Socioeconomic considerations would divide the Common/t transmitted Camp[v/obacte? litus SSp. jejani H('') L(?) infections in categories t and II in yet another way. Enterobius term/cularis L L Infections that are commonly transmitted in affluent Enteroviruses, L H communities (in Europe, for instance) that enjoy high Pathogenic Escheric/ria coli' H H standards in sanitary facilities and hygiene might be Giardia lamb/ia L L expected to be reduced insignificantly by the Rotavirus L(?) 2 introduction of limited sanitary improvements in poor Salmonellae H H communities of the developing countries. An approxi- Shigel/o sonnei M M mate division on these grounds is shown in table 2-6. Yersinia enterocolitica H(?) H In some cases the reasons for this division are clear (the Rare/c transmitted salmonellae, for instance, continue to be transmitted Balantidium coli L (?/ L from animals to man in affluent communities through Entamoeba histoictica L L contaminated foodstuffs), whereas in other cases (such Hy.menolepis nana L L as the continued transmission of Shigella sonnei Salmonella typhi H M throughout Europe) they are obscure. Shigella (other than sonnei) M M The most useful division of categories I and II has Vibria cholerae H M nevertheless proved to be one based on ID50, even though knowledge of the ID50 for infections affecting L LowU M medium H high. malnourished peasant children in the tropics is a. Includes polio-, echo-, and coxsackieviruses. nonexistent. With ID50 as the criterion, categories I and b. Includes enterotoxigenic. enteroinvasive. and enteropatho- II break in a way that makes theoretical sense and also genic E. co/i. ENVIRONMENTAL CLASSIFICATION OF INFECTIONS 37 correlates in some degree with the likely effects of hygiene are not ideal (see figure 2-5). It is therefore improved excreta disposal facilities. likely that changes in excreta disposal technology will The transmission characteristics of the first five have little effect on the incidence of these infections if categories are illustrated in figure 2-4, in which the such changes are unaccompained by sweeping changes typical survival, latency, and multiplication features of in personal cleanliness, which, in turn, may require the groups of infections are shown. These factors, in major improvements in water supply and housing, and turn, affect the "length" of particular transmission major efforts in health education. cycles. Length has spatial as well as temporal But what subsequently happens to excreta-how implications, in that a long transmission cycle increases they are transported, treated, and reused is of less the opportunity of an infection's spreading over a wider importance for this group than the transmission of area, thus changing the pattern of risk. These issues are infection in the home. Although transmission can and developed in the next chapter, and are represented here does occur by more complex routes, most transmission in figure 2-5, in which the relative efficiency of in category I is direct, from person to person, and thus sanitation improvements in controlling the various the provision of hygienic toilets alone will have categories of infection is also indicated. Each category negligible impact. A qualification of category I must in table 2-2 implies some minimum sanitary require- follow this statement: categories I and ii grade into ments for control of the diseases within it and often each other and actually form a continuum (see a control measures ancillary to excreta disposal facilities further explanation in the next section). In particular, that further contribute to success. These requirements the parasitic protozoa have some features of both are elaborated in the discussion that follows. groups. One extreme of the category I parasites is the pinworm, Enterobius, whose sticky eggs are laid on the Categorv I anal skin by emerging females, so that transmission is by way of scratching fingers rather than by excretion of These are the infections that have a low ID50 (<102) eggs in the feces. At the other extreme is Giardia, and are infective immediately upon excretion. We associated with well-documented, waterborne out- argue that these infections may spread easily from breaks of diarrhea, and therefore presumably subject person to person whenever personal and domestic to partial control by excreta management. Infective organisms Category 11 m The infections in this category are all bacterial. They II Lying. bL as yet2ninfect;ve stages (latency). L'vng bt c yt niTeciv sags (laeny) have medium or high ID50S () 10 ), and so are less Environmentacl likely to be transmitted by person-to-person contact category X than are category I infections. The bacteria are TandI ~persistent and can multiply, so that even the small land TT' numbers remaining a few weeks after excretion can, if they find a suitable substrate (such as food), multiply to form an infective dose. Direct transmission routes are important, but so too are others with longer environmental cycles, such as the contamination of water sources or crops with fecal material (see figure 2- 5). The control measures listed in table 2-2 for category 1V ' IN DOMESTIC ANIMALS I are important with the added provisions of sound IN DOESI _N excreta treatment and reuse practice. But, as in category I, changes in excreta disposal and treatment " St practices alone may have little effect on transmission. Numbers A " Control measures may most affect those infections of .' > LS ___ X///S/ that-as noted earlier are not normally transmitted organisms L among affluent groups in Europe or elsewhere: Ttme > cholera, typhoid, and shigellosis (other than S. '- -o. : Any monitoring or evaluation program would do well Figure 2-4. Persistence outside the host oJfexcreted to examine these, rather than infections with pathogens (categories I- VJiom table 2-2) over time nontyphoid salmonellae or pathogenic E. coli. 38 HEALTH HAZARDS OF EXCRETA 'Sanitary barrier' <\\//X~~~~~~~~~~~~~~~~ \J VI Figure 2-5. Lengthanddispersionoftranismission cyclesofexcretedi,fectionis(categoriies I-V.-forom Table2-2). The possible efficacy of improved excreta disposal is indicated by the "sanitary barrier" The criteria used to differentiate categories i and ii II, the role of sanitation improvement is to interfere have been ID50 and length of the environmental cycle, with the efficiency of the longer cycles and thus obtain a factors with predictive value for the efficacy of greater overall benefit than that possible for category 1, sanitation as a control measure. The reason that in which these longer cycles have little significance. categories I and II do not form tidy groups is that the persistences of the pathogens involved vary. The Category III extreme category I case-an environmentally fragile organism with a low ID,,-will clearly tend to be This category contains the soil-transmitted hel- spread in a familial or similar tight pattern and will minths, which are both latent and persistent (see figure depend for its control more on personal cleanliness 2-4). Their transmission has little or nothing to do with than on sanitation. (An extreme example, though not personal cleanliness because these helminth eggs are excreta-transmitted, can be found in the venereal not immediately infective to man. Domestic cleanliness diseases, which do not survive in the environment and is relevant only as it concerns the preparation of depend on intimate contact for their spread.) However, vegetables grown in fields enriched by human excreta an environmentally persistent organism with a low or the maintenance of latrines in conditions that do not ID,0 will lead to infection difficult to reduce either by allow helminth eggs to remain in the vicinity for the sanitation or personal and domestic cleanliness. Many duration of their latency. If eggs are not deposited in excreted viruses exemplify this pattern and pose such soil, or other suitable media, transmission will not major problems of control that induced immunity may occur. Any kind of latrine that contains or removes be the best solution (this is certainly the case for excreta and does not permit contamination of the floor, poliomyelitis and probably also for infectious hepatitis yard, or fields, will therefore limit transmission. and rotavirus diarrhea). For the infections of category Because the persistence of helminth eggs is so long (see ENVIRONMENTAL CLASSIFICATION OF INFECTIONS 39 table 2-3), it is not sufficient simply to prevent infected egg can give rise to many infective larvae. A fresh feces from reaching the yard or fields: any fecal thousandfold multiplication is not uncommon, and product that has not been adequately treated must not effective transmission can continue at low con- reach the soil. In societies that reuse their excreta on tamination levels. The requirements for adequate the land, treatment prior to application is therefore excreta disposal, in terms of the percentage of all feces vital. Effective treatment for the removal of helminth reaching the toilet, may therefore be demanding. eggs generally requires waste stabilization ponds or thermophilic digestion,4 although prolonged storage Category VI will inactivate the eggs of many species. The excreta-related insect vectors of disease form Category IV three main groups. In the first of these, the cosmopolitan Culex pipiens complex of mosquito Category iv is for the beef and pork tapeworms. Any species preferentially breeds in highly contaminated disposal system that prevents untreated human excreta water and is medically important as a vector of the from being eaten by cattle and pigs will control the worm (Wuchereria bancrojti) that causes Bancroftian transmission of these infections (see figure 2-5). Cattle filariasis. The other two groups, flies and cockroaches, are likely to be infected in fields treated with sewage proliferate where feces are exposed. Both have been sludge or effluent and may also eat feces deposited in shown to carry numerous excreted pathogens on their the cowshed. Pigs are likely to become infected by feet and in their intestinal tract, but their role in eating human feces deposited around the dwelling or in actually spreading disease from person to person is the pigpen. The provision of toilets to which pigs and disputed (though their nuisance value is certain). Flies cattle cannot have access, and the treatment of all have been implicated, however, in the transmission of wastes prior to land application, are the necessary eye infections and in infecting and spreading skin control methods. Measures to prevent birds, especially lesions. The control measures implied for insects are gulls, from feeding on trickling filters and sludge drying those sanitary improvements of differing sophisti- beds and subsequently depositing tapeworm eggs in cation which prevent their access to excreta. In general, their droppings on pastures are also required. In the the simpler the facility, the more care is needed to absence of the measures described above, however, the maintain it insect-free. Cockroaches, flies, and Culex thorough cooking of beef and pork is the most pipiens mosquitoes often have breeding places in important control measure. Personal and domestic addition to those associated with excreta disposal and cleanliness, except the use and maintenance of safe will in many cases elude control by disposal toilets, are ineffective controls. improvements alone. Category V Summary This category contains the water-based helminths, The correlation of the environmental features of the which need an aquatic host or hosts to complete their categories with the length and spread of transmission life cycles. Control is achieved by preventing untreated routes has been indicated in figure 2-5, and the excreta or sewage from reaching water in which these discussion has emphasized the importance of com- aquatic hosts live (see figure 2-5). Any land application plementary controls for most diseases. If excreta or dry composting system will therefore reduce disposal alone is improved, however, likely control for transmission. There are two complications. First, in all each category is as follows: cases except Schistosoma mansoni and S. haematobium, Category Control animals are an important reservoir of infection (see I Control tables 1-9 and 2-3), and any measures restricted solely I N Slight to moderate to human excreta can only have a partial effect. Second. II Moderate to great in the case of S. haernatobiuim it is the disposal of urine, IV Moderate to great far more difficult to control than the disposal of feces, v Moderate that is important. Because multiplication of these VI Slight to moderate helminths takes place in the intermediate hosts (except The outstanding difference is between categories I and in the case of the fish tapeworm, Diphyllobothrium), one ii, which depend strongly on personal and domestic cleanliness, and the other categories, which do not. The 4. See the discussion of these processes in chapters 5 and 6. central changes necessary to control infections in 40 HEALTH HAZARDS OF EXCRETA categories ini and iv are relatively simple namely, the Eyles, D. E., Jones, F. E. and Smith, C. S. (1953). A study of provision of toilets which people ol'all ages? will use anid Endamoeha histolytica and other intestinal parasites in a keep clean, and the treatment of fecal products prior to rural west Tennessee community. Aimerican Journal Jo recycling on the land. The reason that reports on the Tropical Medicine and Hygiene, 2, 173-190. effects of latrine programs often do not show a marked 'achem, R. . A., McGarry, M. G. and Mara, D. D. (1977). Water, Wastes and Health in Hot Climates. London: John decrease in the prevalence of the infections in Wiley. categories in1 and 1v6 is that, although latrines have Gordon, J. E., Behar. M., Scrimshaw, N. S., Guzman, M. A. been built, they have typically neither been kept clean and Ascoli, W. (1964). Acute diarrhoeal disease in less nor been used by children or by adults when working in developed countries. Bulletin of the World Health the fields. Organization, 31, 1-28. Henry, F. J. (1981). Environmental sanitation, infection and Literature Cited nutritional status of infants in rural St. Lucia, West Indies. Transactions of'the Royal Society .' 1 I Medicine and Arfaa, F., Sahba, G. H., Farahmandian, 1. and Jalali. H. Hvgiene, 75, 507-513. (1977). Evaluation of the effect of different methods of Hollister, A. C., Beck, M. D., Gittelsohn, A. M. and Hemphill, control of soil-transmitted helminths in Khuzestan, E. C. (1955). Influence of water availability on \',L southwest Iran. American Journal T, I T .. ; Medicine and prevalence in children of farm labor families. American Hygiene, 26, 230-233. Journal oJ'Public Health, 45, 354-362. Azurin, J. C. and Alvero, M. (1974). Field evaluation of Hornick, R. B., Music, S.I., Wenzel, R., Cash, R., Libonati. J. environmental sanitation measures against cholera. P., Snyder, M. J. and Woodward. T. E. (1971). The Broad Bulletin of' the World Health Organization, 51, 19-26. Street pump revisited. Response of volunteers to ingested Barbosa, F. S., Pinto, R. and Souza, 0. A. (1971). Control of cholera vibrios. Bulletin of the New York Academy oJ schistosomiasis in a small northeast Brazilian community. Medicine, 47, 1181-1191. Transactions of the Royal Society' of' Tropical Medicine and Jeffery, G. M. (1960). A three-year epidemiologic study of Hygiene. 65, 206-213. intestinal parasites in a selected group of mental patients. Bradley, D. J. (1977). Health aspects of water supplies in American Journal of Hygiene, 71, 1-8. tropical countries. In Water, Wastes and Health in Hot Katayama, Y. (1955). Sanitary treatment of human excreta Climates, eds. Feachem, R. G. A., McGarry, M. G. and by heating process. 16. Effect of the treatment applied to a Mara, D. D., pp. 3-17. London: John Wiley. farm village (Part 1). Japanese Joturnal of the Nation's Brooke, M. M., Donaldson, A. W. and Brown, E. (1954). An Health, 24, 1-12. amebiasis survey in a Veterans Administration Hospital, Kawagoe, K., Nishi, H., Shibata, E. and Yamada, S. (1958). Chamblee, Georgia. with comparison of technics. On the effect of nightsoil treatment upon heating process American Journal of' Tropical Medicine and Hygienie, 3, utilizing surplus midnight electric power upon the 615-620. incidence of parasitic infection of farmers. Japanese Brooke, M. M., Healy, G. R., Levy, P., Kaiser, R. L. and Journal of'the Nation's Health, 27, 162-165. Bunch, W. L. (1963). A sample survey of selected areas in Khalil, M. (1931). The pail closet as an efficient means of and near Little Rock, Arkansas, to assess the prevalence of controlling human helminth infection as observed in Tura Entamoeba histolytica. Bulletin oJ' the World Health Prison, Egypt, with a discussion on the source of Ascar-is Organization, 29, 813-822. infection. Annals of Tropical Medicine and Parasitology, 25, Chandler, A. C. (1953). An evaluation of the effects, after two 3 5-62. years, of sanitary improvements in an Egyptian village. Kleevens, J. W. L. 11966). Re-housing and infections by soil Journal of'the Egyptian Medical Association, 36, 357-367. transmitted helminths in Singapore. Singapore Medical (1954). A comparison of helminthic and protozoan Journal, 7, 12-29. infections in two Egyptian villages two years after the Koopman. J. S. (1978). Diarrhea and school toilet hygiene in installation of sanitary improvements in one of them. Cali, Colombia. American Journal of Epidemiology, 107, Americani Journal of' Tropical Medicine and Hygiene, 3, 412-420. 59-73. Kourany, M. and Vasquez, M. A. (1969). Housing and Cort, W. W., Schapiro, L. and Stoll, N. R. (1929). A study of certain socioenvironmental factors and prevalence of reinfection after treatment with hookworm and Ascaris in enteropathogenic bacteria among infants with diarrheal two villages in Panama. American Journal of 'Hygiene, 10, disease in Panama. American Journal of' Tropical Medicine 614-625. and Hygiene, 18, 936-941. 5. Otcoursebabiesandveryyoungchildrenareunabletouseatoilet. Kumar, P., Sehgal, B. S. and Singh, R. (1970). Bore-hole Health education programsmust include advice tomothers on how to disposal of excreta of children and diarrhoeal morbidity in dispose of their children's excreta in a suitablv hygienic way. a rural community. Environmental Healtlh, 12, 155-159. Kutsumi, H. (1969). Epidemiological study on the preventive 6. See the next chapter and table 2-t. effect of thiabendazole as an ovicide against human ENVIRONMENTAL CLASSIFICATION OF INFECTIONS 41 hookworm, Trichurtis and Ascaris infections. Japanese Schneider,R.E.,Shiffman,M.andFaigenblum,J. (1978). The Journal of Medical Science and Biology. 22, 51-64. potential effect of water on gastrointestinal infections McCabe, L. J. and Haines, T. W. (1957). Diarrhoeal disease prevalent in developing countries. American Journal of control by improving human excreta disposal. Public Clinical Nutrition, 31, 2089-2099. Health Reports, 72, 921-928. Scott, J. A. and Barlow, C. H. (1938). Limitations to the Mackie, T. T., Mackie, J. W., Vaughn, C. M., Gleason, N. N., control of helminth parasites in Egypt by means of Greenberg, B. G., Nenninger, E. S., Lunde, M. N., Moore, treatment and sanitation. American Journal oJHygiene, 27, L. L. A., Kluttz, J. A. and Taliafero, M. 0. (1956). Intestinal 619-648. parasitic infections in Forsyth County, North Carolina. Shiffman, M. A., Schneider, R., Faigenblum, J. M., Helms, R. IV. Domestic environmental sanitation and the prevalence and Turner, A. (1979). Field studies on water sanitation of Entamoeba histolytica. American Journal of Tropical and health education in relation to health status in Central Medicine and Hygiene, 5, 29-39. America. Progress in Water Technology, 11, 143-150. Mathur, T. N. and Kaur, J. (1972). The epidemiology of Stewart, W. H., McCabe, L. J., Hemphill, E. C. and DeCapito, amoebiasis in an urban area. Indian Journal of Medical T. (1955). Diarrheal disease control studies. IV. Research, 60, 1t34-1137. Relationship of certain environmental factors to the Moore, H. A., de la Cruz, E. and Vargas-Mendez, 0. (1965). prevalence of Shigella infection. American Journal oJ Diarrheal disease studies in Costa Rica. IV. The influence Tropical Medicine and Hygiene, 4, 718-724. of sanitation upon the prevalence of intestinal infection Sweet, W. C., Cort, W. W., Schapiro, L., Stoll, N. R. and Riley, and diarrheal disease. American Journal of Epidemiology, W. A. (1929). A study of the effect of treatment and 82, 162-184. sanitation on the level of hookworm infestation in certain Otto, G. F., Cort, W. W. and Keller, A. E. (1931). areas in Panama. American Journal oJ Hygiene Environmental studies of families in Tennessee infested Monographic Series no. 9, 98-138. with Ascaris, Trichuris and hookworm. American Journal van Zijl, W. J. (1966). Studies on diarrhoeal diseases in seven of Hygiene, 14, 156-193. countries by the World Health Organization Diarrhoeal Otto, G. F. and Spindler, L. A. (1930). Effect of partial Disease Advisory Team. B,,h. ',. of the World Health sanitation on infestation with intestinal parasites in Organization, 35, 249-261. Southwest Virginia. Southern Medical Journal, 23, Villarejos, V. M., Pelon, W., Picado, B., Ortiz, J. G., Jimenez, 556-560. R. and Navas, H. (1966). Epidemiologic investigation of an Rosenberg, A. I. (1960). Sanitary and hygienic measures for outbreak of infectious hepatitis in Costa Rica. American the control of focal ascariasis. Meditsinskaia Parazitologiia Journal of Epidemiology, 84, 457-466. i Parazitarnye Boleznii, 29, 143-149. Weir, J. M., Wasif, I. M., Hassan, F. R., Attia, S. D. M. and Sahba, G. H. and Arfaa, F. (1967). The effect of sanitation on Kader, M. A. (1952). An evaluation of health and ascariasis in an Iranian village. Journal of Tropical sanitation in Egyptian villages. Journal of the Egyptian Medicine and Hygiene, 70, 37-41. Public Health Association, 27, 53-122. Schliessmann, D. J., Atchley, F. O., Wilcomb, M. J. and WHO (1979). Human Viruses in Water, Wastewater, and Soil. Welch, S.F. (1958). Relationship of environmentalJactors to Technical Report Series no. 639. Geneva: World Health the occurrence of enteric diseases in areas of eastern Organization. Kentucky. Public Health Monograph no. 54. Washington, D.C.: Government Printing Office. 3 The Risks of Excreta to Public Health THE DISCUSSION has dwelled at length on the survival mother has had six babies, one of whom died at the age of pathogenic organisms in excreta, on which there is a of 15 months after a sudden attack of diarrhea; a good deal of information. This is the main health- school-age child died in a cholera epidemic that swept related concern of the engineer when he is designing the region 4 years ago. sanitary facilities. The planner and economist have a It is particularly difficult to control excreta in this greater interest in epidemiological risk: if, in a given damp environment-most feces are deposited close to situation specific changes in excreta disposal are made, the house, and the younger children urinate in the how much less disease will there be? This question can nearby canals. Several years ago a government be rephrased in two ways, the first of which can be campaign to provide pit latrines was mounted, and one answered readily and the other only with the greatest was dug near the family's house. They used it for a difficulty. The easier question is: what are the disease while, until the pit flooded over in the monsoon season problems associated with excreta, and thus, by and a large quantity of fecal material was spread implication, with inadequate excreta disposal facilities around the house. It was during the flooding that the or inadequate personal or domestic cleanliness? The cholera epidemic occurred; its sad consequences for difficult question concerns the health benefits of the family, together with the unpleasant mess from the improved sanitation: how much disease will be latrine, discouraged further use of the facility. The next eradicated if a given sanitary improvement is government recommended that a concrete aquaprivy undertaken? These questions are considered in general be built above the ground to avoid the floods, but the terms in this chapter. family could not afford this and returned to defecating close to the house during the day. Nocturnal excreta were collected in a bucket and deposited in a nearby Illustrative Sketches fishpond. How does this situation affect the family's health? The effects of the diseases accompanying unsafe All the children get diarrhea several times a year, the exereta disposal are dramatized in the sketches of two parents less regularly. The worst occasion was when imaginary settings that follow. Formal case studies of two of the girls got it at the same time. The younger sanitation and health are then outlined before a one, 15 months old, seemed to wither overnight, and discussion of the benefits of sanitation improvements. she died the next day. Death was from rotavirus infection. (Why it is more often lethal in the tropics than in temperate countries is unclear: perhaps the poor sanitary facilities in this case gave the child an In areas of Southeast Asia with high rainfall, a overwhelming dose of the virus; perhaps malnutrition, perennially hot climate, and a main cereal crop of ubiquitous during the weaning period in communities irrigated rice, the diverse health hazards from excreta such as this one, complicated the attack?) Most of the are illustrated by the following case history, a diarrheas are watery, sudden attacks, but last year the composite of several real sites and people. A family lives grandmother who shares the house with the family, in a palm-roofed, wooden house surrounded by rice was one of several people in the village who came down paddies and small irrigation channels, one of which, with a more painful diarrhea with bloody stools, from flowing near the house, acts as the domestic water which she nearly died. Medicine from the dispensary supply. There are four children in the family: the four miles away helped initially, but she remained ill for 43 44 HEALTH HAZARDS OF EXCRETA weeks. This attack was from bacillary dysentery temperatures are at least as high as in the Asian village (shigellosis), though to distinguish it from amebiasis just visited. The houses cluster on a mound rising from would have required laboratory diagnosis. surrounding irrigated areas. The irrigation is from All these illnesses were dramatic, but the family has water brought from afar by great rivers, not from heavy several health problems of which they are barely aware. rainfall, and the ground is baked hard where it has not The eldest son has not grown properly: although he is recently been irrigated. Within the village the streets 23, he looks as if he were in his early teens; his belly is are narrow and unpaved, and large quantities of debris always grossly swollen, and the dispensary attendant lie around. can feel his hard liver and spleen under the taut skin of The family selected consists of the parents, three his abdomen. His condition is caused by schistoso- children, and some elderly relatives. This family has miasis, which is spread from one person to another by a also suffered the death of children from diarrheal tiny snail living in the damp grass beside the canals and disease. (Indeed, it would be difficult to find a tropical in the water itself. Several members of the family are or subtropical area in which this is not a problem.) infected, but only this boy shows signs of the disease. As in Asia, schistosomiasis and elephantiasis are In this region of paddies and canals, fish present. These are of somewhat different varieties, but sometimes cooked, sometimes pickled raw in create disability in similar ways. Although intestinal vinegar is an acceptable and available food. A schistosomiasis occurs here, two of the younger portion of the fish consumed is from ponds fertilized children have a urinary form of the disease and pass with human feces, and this practice has caused some of blood in their urine every day. This looks more serious the family to be infected by the liver fluke Cloniorchis than it is (in fact, the blood loss is small); however, the sinensis. Another helminth that the family harbors in children do suffer the pain and inconvenience of having large numbers is Fasciolopsis buski, an intestinal fluke to get up frequently to urinate at night. Not too long acquired from eating raw aquatic vegetables. Neither ago their uncle had to go to the hospital in the nearby of these parasites causes catastrophic illness, but the city, where he was told that he had inoperable cancer of diversion of nutrients to the parasites and their other the bladder. He died a very painful death, and the insidious effects make life less satisfactory than it surgeon told the family his death may have been a late otherwise would be. The family also suffers from other consequence of the same infection causing blood in the intestinal worms occurring in even greater numbers urine of the children, but that only a few unfortunate and causing more illness (these are discussed in relation people developed cancer from the infection. to another family, below). The helminths associated with fish and aquatic One more infection attends the family's lack of safe plants that plagued the previous family are absent from excreta disposal. Within the pits of the latrines that this environment, but microscopic examination of the have been flooded and abandoned, the liquid waste is feces of the family show hookworm (Ancylostoma), colonized by mosquito larvae of the Culex pipiens roundworm (Ascaris) and whipworm (Trichuris) eggs group. When the adult mosquitos bite the members of in large numbers. The hookworm eggs are especially the household, they transmit into the bloodstream the numerous the infection has been picked up by larvae of a parasitic worm (Wuchereria bancrofti) that walking barefoot on land that has been used for lives in the tissues under the skin of the legs and defecation and that has been kept moist enough by the elsewhere, particularly in the lymph nodes, where it nearby drains and canals for the worm larvae to blocks the lymphatic flow. Tissues near the blockage develop in the soil. The mother has a particularly heavy consequently become swollen from the accumulation infection. The worms inhabit the small intestine where of lymph, and some affected people develop massive they attach themselves to the intestinal wall; they are elephantiasis. The father of the family is troubled by messy feeders, and a large amount of the blood they this in his right leg, which is so swollen that he cannot suck for their growth and production of their eggs work in the fields as productively as he could before. passes straight through their bodies and is lost into the intestinal lumen. As a result the blood losses from this infection are high-indeed. the mother's loss is twice as A Nor-th African fiimily heavy as that from menstruation and, because her diet The next region visited is quite different in general is not overly rich in iron, she has become anemic and appearance, but behind this exterior are certain unable to work as hard as a fit person. The same is true similarities in the disease pattern. The village entered is of one of the children: his abdomen is swollen; he a cluster ofmud brick houses located in the subtropics. cannot run fast enough to keep up with the other It is quite cold in the winter though summer children, and his condition gives considerable cause for RISKS TO PUBLIC HEALTH 45 anxiety. Some other infection in addition to the their way onto vegetables that are eaten raw. Eggs also hookworm might well claim his life. occur in the mud and sand of the compound, where All the family have roundworms. These parasites are they readily contaminate the hands of crawling babies. quite large (over 100 millimeters long), and every now Another intestinal worm somewhat important in and then one of the younger children passes one in the this milieu is the beef tapeworm (Taenia saginata), stool. This elicits little more than comment, since there which is acquired from an infected cow by eating its is no obvious illness except pain in the abdomen, a beef undercooked (this readily occurs when a large complaint difficult to ascribe to a specific cause. What piece of meat is roasted). The adult tapeworm matures is certain is that the worms are absorbing a good in the intestines, adding segments to its length and percentage of the nutrients the children need, and there competing for the family members' limited nutrients; is also the risk that the worms will get stuck in the its eggs, often contained in its swollen segments, are narrowest part of the intestine and block it, thus shed in large numbers when a tapeworm segment necessitating a faraway surgeon's attention. The family wriggles out of the anus. These worm segments are are well aware of the problem, and have often visited frequently ingested by browsing cattle; the worm the dispensary to get medicine. But in the absence of undergoes further development within the muscles of instruction and better methods of disposing of their the cow; the beef is inadequately cooked and eaten, and excreta, the infection comes back every few months. the cycle of infection is resumed. The family's religion The adults seem to have become somewhat immune to prohibits the eating of pork and so they are spared its reinfection, and the children carry the brunt of the tapeworm (Taenia soliuin), whose larvae can develop in recurrence. human muscles-an added and sometimes fatal hazard. Most of those, especially the children, who have Except in the case of hookworm infection with its roundworms also have whipworm infections. These dramatic blood loss, all these helminth infections are so little worms, found mostly on the wall of the colon and long lasting and ennervating that it is difficult to assess rectal passage, have an uncertain effect on most of the their specific damage; they are all infections that are family, generally adding to the burden of other often underrated because of their widespread occur- parasites. Some while ago a neighbor's child picked up rence and insidious, drawn-out course. The family also a very heavy infection with the whipworm. The rectal suffers from several acute infections, not only diarrheas passage gradually prolapsed (that is, got partly pushed but also typhoid and hepatitis. The incidence of out of the anal orifice), which was both painful and typhoid in the village is particularly high because of unsightly, while an intractable diarrhea that had begun inadequate excreta disposal. In addition, the presence some months earlier persisted and made the child very of schistosomiasis in the inhabitants modifies typhoid anemic. A concurrent amebic infection led to some and lengthens its course, and up to one in every twenty- confusion over what was causing which symptoms, but five people may become a typhoid carrier in some of the prolapse was certainly not a regular feature of these villages, a rate which is an order of magnitude amebiasis and the diarrhea could have been due to higher than seen elsewhere. Consequently, typhoid is either cause. extremely common, no less severe than elsewhere, and What arrangements are made for excreta disposal an appreciable cause of mortality. Hepatitis also here? Bore-hole latrines were made for each family's occurs frequently: in the younger children it rarely use but they filled up rather quickly and were then so produces serious symptoms, but in adults the patient unpleasant that no one wanted to use them. In any may be bedridden for weeks or months, and sudden case, the latrines were in or near the houses and, death is not unknown. because the families spend much of the day in the fields One feature that clearly emerges from the account of working on their rice and other crops most felt that it this family in North Africa is the extent to which it would be an unreasonable waste of their time to come shares in the excreta-related health problems of the all the way back to the house to defecate. It is also more family in Southeast Asia. Indeed, as in few other disease convenient to relieve themselves in the field because patterns, there is a sameness to most of the serious, their religion insists that they wash the anus after frequently transmitted, excreted infections that cannot defecation, and there is no water readily available for be avoided: certain infections are peculiar to particular this purpose within the compound. Because of the localities, but the pattern of diarrheal disease, enteric varying sites for defecation, roundworm and whip- fever, numerous viral infections, and intestinal worms worm eggs are spread widely throughout the is repeated worldwide. Of the major excreted environment. The eggs are extremely resistant, even in infections, only cholera and schistosomiasis have the harsh climate of this part of the world, and find variable and patchy distributions. 46 HEALTH HAZARDS OF EXCRETA Table 3-1. Maximum prevalence of excreted pathogens (from table 2-2) bv age in indigenous populations of endemic areas Age group of highest prevalence of infection (years) Babies C ii., Teenagers Adults Patlhogen (0-2) (3-12) (13-19) (20+) CATEGORY I Balantidium coli * Entamoeba histolytica * * Enterobius vermiclularis * * Enterovirusesa * * Giardia lamblia * Hepatitis A virus * * * Hymenolepis nana * * Rotavirus * CATEGORY 11 Campylobacterfetus ssp. jejuni * * Pathogenic Excherichia colib * * Salmonella S. typhi * * Other salmonellae * * * * Shigella spp. * * Vibrio cholerae * Yersinia enterocolitica * * CATEGORY II] Ascaris lumbricoides * * Hookwormsc * * * Strongy loides stercoralis * * Trichuris trichiura * CATEGORY IV Tuenia saginata and T solium * * CATEGORY V Clonorchis sitensis I) , i., P. I . .,*. latum * Fasciola hepatica * * * Fasciolopsis buski * * Gastrodiscoides hominis * Heterophyes heterophves * Metagonimus yokagawai * Paragonimus uestermani * Schistosoma spp. * * a. Includes polio-, echo-. and coxsackieviruses. b. Includes enterotoxigenic, enteroinvasive, and enteropathogenic E. coli. c. Ancylostoma duodenale and Necator americanus. Children and Excreta Disposal found in people of all ages, many are concentrated in particular age groups. The age groups most afflicted by Many of the excreted infections examined in this the main excreted infections in areas where these book have a markedly nonuniform distribution among infections are endemic are shown in table 3-1. The data different age groups. Although all the infections are ofthe table clearly show that many ofthese illnesses are RISKS TO PUBLIC HEALTH 47 primarily childhood infections, or that the infections happy to use and health education for mothers, so that afflict children as well as adults. This fact has the they will compel their children to use them. Health greatest relevance for disease control through improve- education for school-aged children could also be ments in excreta disposal. effective here, and it is essential that all schools have In all societies children below the age of about 3 will well-maintained latrines as positive examples for the defecate whenever and wherever they feel the need. A children.' proportion of these children will be excreting substantial quantities of pathogens. In some societies these children's feces are regarded as relatively inoffensive, and the children are allowed to defecate The transmission cycles typically followed by the anywhere in or near the house. In this case it is highly infections in categories I through v (table 2-2 and figure likely that these feces will play a significant role in 2-5) have been compared and discussed and the shorter transmitting infection to other children and adults. or tighter cycles that categories l and II may follow over This applies not only to those infections without a categories III to v have been indicated. The implication latency period but also to infections such as ascariasis, is that categories III to V are associated with a wider in which the defecation habits of children may spread of their infections, a factor important in the determine the degree of soil pollution in the yard and selection of appropriate excreta disposal technology around the house and thus the prevalence and intensity and, in particular, in assessing the willingness of an of infection in the household. In other societies individual family to adopt an innovation. If, on the one strenuous efforts are made to control and manage the hand, a household head believes, or can be persuaded stools of young children, either by making them wear to believe, that the adoption of a new technology will diapers (nappies) or by cleaning up their stools bring appreciable health benefits to his family, whenever they are found. Either of these reactions regardless of what is taking place in the neighborhood, should have an important controlling influence on the then he will be more willing to innovate. If, on the other intrafamilial transmission of excreted infections. hand, it is clear that his action alone will have a Between these two extremes is a range of negligible effect on his family's health, he is more likely intermediate behavioral patterns by which adults react to sit back and await clear evidence that a viable and to the stools of young children. In most poor effective improvement program is being carried out communities, the pattern is closer to the first reaction throughout his neighborhood. than to the second. The relevant response of In cases in which most pathogen transmission is government and other responsible agencies where intrafamilial-as in category I and, to a lesser extent, these attitudes prevail should be health education category iI it can be expected that improvement in programs to encourage in mothers the belief that the excreta disposal and cleanliness in an individual family stools of young children are dangerous and should be may lead to health benefits for that family. In fact, as we hygienically disposed of. Although the problem is have already argued, cleanliness is probably more primarily in attitudes and behavior, the provision of important than excreta disposal facilities per se in the some form of toilet for the disposal of a child's stool reduction of category I (and to a lesser extent category and, perhaps more important, a convenient water iI) infections, and therefore it is changes in hygienic supply will greatly assist child hygiene. behavior that may bring the greatest benefit to a single Children over 3 years in age, in contrast, are capable family in isolation from widespread changes in the of using a toilet if one of suitable design is available. community's sanitation. Children of 3 to 12 years frequently do not use There is one infection from categories III to v available toilets because they find their use incon- ascariasis-which, although potentially having a long venient and it is not encouraged by adults; they are transmission cycle, is frequently transmitted within the afraid of falling down the toilet's hole or of being family and diminishes with improvements in excreta attacked by the pigs that may live next to the latrine; disposal facilities without accompanying changes in they cannot use a toilet not designed to their scale; or personal cleanliness. Work in China and the US in the they are prevented from doing so by adults who want 1920's and 1930's showed that poor families, who used to avoid cleaning up the toilet area after them. their latrines and prevented their children from As with very young children, it is of vital importance defecating in the yard, had significantly lower that the stools of children over age 3 be hygienically 1. Indeed, the whole subject of health education, so difficult to disposed of because some will be rich in pathogens. The discuss incisively, is crucial to thefull realisation ofthe potential health solution lies in providing both toilets that children are benefits of improved excreta disposal facilities see Chapter 8. 48 HEALTH HAZARDS OF EXCRETA intensities of Ascaris infection than their neighbors several changes to benefit the community's health. To (Otto, Cort and Keller 1931; Winfield 1937). Similar allocate all the health benefits to improved sanitation reductions on an individual family basis can be alone would therefore be unjustified. Conversely, a expected from the adoption of improvements in excreta study that demonstrates no health improvement after disposal today. There are other specific circumstances appropriate changes in sanitary facilities cannot in which a given infection may readily be reduced by validly imply that such changes are useless. The the independent action of a single family. An example is facilities may have been unused for lack of health hookworm in rural India, where in many villages much education or may have been improperly sited-it is of the infection occurs when barefoot people visit the often a mistake to generalize from a particular local communal defecation grounds on the edge of the result. community. A family which installs a pit latrine and no The economist ideally wishes to use data on health longer visits the defecation ground may substantially benefits to decide priorities in resource allocation, and reduce its exposure to hookworm infection. These the total health benefits are needed for such a decision. cases demonstrate that, in planning and implementing However, health as such is not measureable (except, an excreta disposal program, officials may find it useful possibly, in the form of statistics on the growth of to identify infections for which individual household infants), and it is diseases that are studied instead. action may be particularly effective. These infections Because sanitation affects a range of diseases not all might then be monitored and the family results used as measurable in a single study, a few indicator or index part of a community propaganda exercise (for diseases are usually chosen to assess benefits. More example: "the Sanchez family has adopted the new often still, particular disease agents such as -Ji.'gt .i: latrine and improved their domestic hygiene and they bacteria or worm eggs are assessed in the feces. The now have less roundworms than their neighbors>). resulting measures of how infection rates change as sanitation is applied are several removes from health Health Benefits of Sanitation benefits pe- se. and the intermediate causal relation- ships are by no means linear. The relation between an Although major health problems are clearly infection and the development of disease depends on associated with inadequate excreta disposal facilities, variables such as: the intensity of infection, nutritional to relate the two causally-in particular, to say what status, other infections, age of the host, and health the health benefits will be from a given proposed care available locally. improvement of facilities-is difficult. The difficulties and the studies attempting to overcome them are The literature reviewed in this section. Critical comments must not obscure the fact that without improved excreta Some of the relevant literature on the assessment of disposal many of the diseases discussed will never be health benefits is listed in table 2-1. Almost none of the overcome, yet other complementary measures and in studies described therc reaches the standards of some cases major social, economic, and political epidemiological demonstration that make a study changes--will generally be required for success. conclusive; melancholy criticism of the limitations of each paper is therefore avoided. Rather, the con- clusions reported in the literature should be taken as an Methodological issues indication of trends. Studies of the health benefits of sanitation in the field An important component of any evaluation, but one have either compared disease levels in communities that is much neglected, is time. The attainment of with varying sanitary facilities or monitored disease comparability between an area that has experienced patterns before and after the improvement of sanitary sanitary interventions and one that has not requires facilities within a community. In both cases the that surveys be done soon after installation of the difficulties in attributing benefits to the improved sanitary facilities. In the common case, observations sanitation have arisen because other variables are often are recorded only for up to a year and are begun associated with the sanitation facilities. People who months after construction. Such information has poor have better sanitation than their neighbors often also predictive value for the long term. If a special campaign have higher incomes, better water supplies, and has been mounted in relation to new facilities, the different habits of cleanliness. Similarly, if a single results may be transiently impressive but may fall off community is followed over time, improvements in the over time. Conversely, the community may take some sanitary facilities are likely to be only one among years to adjust to and use the innovations, so that a RISKS TO PUBLIC HEALTH 49 short-term study fails to demonstrate the real benefits of treating sanitation-related diseases, but these changes bring. Even if these problems are avoided estimates are-small in relation to the estimates of the through long-term study or the observation of work and life lost to these diseases. The latter estimates variations between communities with long-established themselves are subject to great uncertainty, and any differences in excreta disposal patterns, the difficulty of figures put on such losses may be largely spurious. confounding variables arises: it is most unlikely that Two examples may be given. Wagner and Lanoix communities will stay comparable in all differences (1969) attempted to estimate the costs of diarrheal other than excreta disposal and its consequences over disease and found that the largest component was from many years. premature death in children under the age of 2 years. Considering these complexities, it is not surprising There are several means of placing an economic value that studies on the benefits of excreta disposal assessed to death at this age that give widely differing answers. by health changes in the field are almost all of an More recently Latham, Latham and Basta (1977) insufficient standard to be convincing. Few indeed can estimated the cost of Ascaris infection to Kenya. The be described as scientifically impeccable and produc- largest single component was the estimated reduction tive of results inspiring confidence. This discussion of in food absorption and utilization by those infected, methodology might be considered niggling and given as US$4.4 millions yearly, as compared with a academic if most of the published studies gave total of US$0.7 million for all other costs such as concordant results-but this is not the case, and some present treatment, health care, and transport to health studies are frankly contradictory. Again, a detailed care facilities. Yet it is possible to pose reasons for the critique of each study listed in table 2-1 is not given US$4.4 millions varying by ± 50 percent. because these defects in sampling, comparability of It is also possible, however, to make informed samples, and confounding variables recur with such assessments of the comparative benefits of different consistency, whereas the actual use of facilities excreta disposal systems, and this is attempted below. provided is scarcely ever assessed. A further methodo- No cost figures on different excreta disposal systems logical difficulty is that, in studies using recurrent are given here-these may be found in the various medical treatment, observations are made during other documents issuing from the World Bank's periods too short in duration to show long-term investigations of appropriate sanitation technologies.2 outcomes and to detect the large rise in noncompliance It will be clear from our discussion of human behavior with therapy that tends to occur in time. here and in chapter 8 that the greatest determinants of If all the studies in table 2-1 were summarized, the efficacy of alternative facilities are, first, whether however, they would collectively suggest that it is they are used by everyone all the time, and second, reasonable to hope for a halving of the incidence of whether they are adequately maintained. Use will be category iII, iv and v infections through improved dependent on the locality concerned: for instance, in excreta disposal facilities and concomitant supporting urban situations, where alternative defecation sites are programs for facility maintenance and health educ- scarce, it will be easier to ensure widespread use of new ation. If such programs are combined with safe water facilities. There are also both private and public aspects supply and appropriate behavioral changes, the risk to maintenance of all but basic on-site systems, and from some other serious excreta-related diseases can systems vary in their public maintenance needs (some become small, and such illnesses as typhoid and withstand public neglect better than others). cholera (category II) can cease to be endemic. The impact of improved excreta disposal on category l . . infections is likely to be small in the absence of major Best inferences In an optimal case improvements in domestic conditions, which may In the evaluation of the health benefits of excreta imply substantial socioeconomic change in the disposal, an optimal situation would be one in which community at large. everyone uses the facilities all the timne and the town council responsible for their maintenance is meticulous in its duties. A corresponding worst case would be the Limitations in Assessing Health Benefits total lack of sanitation facilities. In both cases, it is the disposal technologies rather than management sys- The planner seeks a clear, preferably monetary, tems that are the objects of comparison. The baseline statement of the health benefits of alternative sanitation improvements. The data are not adequate to 2. See, for example, Kalbermatten, Julius and Gunnerson (1982) provide one. It is quite feasible to list the present costs and Feachem, Mara and Iwugo (1980). 50 HEALTH HAZARDS OF EXCRETA situation will vary greatly in the absence of any water to a treatment plant, oxidation ponds for sewage, sanitary provisions. Where population densities are and batch thermophilic composting for night soils and high, as in many parts of rural Asia and in all the sludges, will give a safe product. Alternative processes world's major cities, the base level of disease caused by in treatment plants are inferior. excreted pathogens will be quite high. On a crude scale of ill health, this situation would be rated at 0. Where conditions include flush toilets, sewers and an efficient Best iiiferences in actUalir' treatment plant-the best case-the resulting health In the real world, of course, systems are not benefits will rate a 10 as long as water supplies are maintained impeccably, nor are facilities invariably adequate for optimal use of the sanitation system. used. Moreover, some systems clearly require less effort Although not adapted to the water use levels needed to maintain and use than others. Cartage in some for the personal cleanliness required to minimize the Japanese towns using vacuum trucks is fully compara- infections of categories I and ii (see table 2-2), pit ble to waterborne sewerage (Kalbermatten, Julius and latrines would, from the viewpoint of health rather Gunnerson 1982). In some cities in other countries, than convenience, approximate the same rating as a however, the great majority of trucks are typically out waterborne sewerage system. Because a pit latrine has of operation. Health benefits are closely tied to no effluent or product, it is in this regard safer than a operation and use, and some societies are better than sewerage system producing large volumes of a polluted others at operating particular systems. If change is effluent that is in general, even in the best treatment contemplated, much greater effort than hitherto plants, not made completely pathogen free. A rating of assumed may need to be allocated to the operation and 9 is given to pit latrines (but this rating does not apply use, rather than the installation, of new facilities. wherever fecal material might soak through latrine Operation and maintenance require both user effort walls to gain access ultimately to drinking water or and municipal endeavor, and the necessary blend wherever flooding or a high water table regularly between these differs according to the chosen recur). technology. A ranking of the various disposal Where composting, double-vault latrines (a rating of technologies by ease of maintenance for the user and 8) are used and are dug out frequently, a residual the municipality, water requirements, and the ideal (as hazard from long-lived helminth eggs persists and discussed in the section above) and actual health benefits are less. Reuse of the compost will further benefits is given in table 3-2. It should be noted that the spread the eggs in the community. The "multrum" ideal benefits vary little among processes when the composting toilet is, again, safe if operated ideally, but facilities are well maintained and used; only bucket in general its risks tend to be greater (hence a rating of latrines are intrinsically and substantially inferior. The 7) because the latrine's continuous process involves proposed ranking of actual benefits reflects variables hazards from insufficiently composted pathogens. leading to neglect of the particular facilities, but this is a An aquaprivy with a retention time longer than a very provisional evaluation, and many other factors month may yield an effluent with a low pathogen must be taken into account in selecting technology for content, but this requires the regular addition of water a given site. The infonned speculation in table 3-2 is to the tank at a rate that will not seriously reduce the intended to stimulate thought about the health-related retention time. Provided that an efficient sludge aspects of technology choice, and to draw attention to removal and treatment system is available, the the disparate advantages of the pit latrine and the resulting health benefits from the aquaprivy might bucket system. approximate 9 on the scale. A septic tank with a retention time of only 1-3 days produces an effluent rich in pathogens and therefore is associated with greater risk (a rating of 8 is assigned). With a bucket- Literature Cited latrine system, major reductions in disease are unlikely, Feachem, R. G. A., Mara, D. D. and Iwugo, K. 0. (1980). even in an ideal world, and a rating of 5 is considered appropriate. A well-managed vault and vacuum-truck Afria. Appropriate Technology for Water Supply and cartage system would be a great improvement, but Sanitation, vol. 7. Washington, D.C.: The World Bank, some risk of spillage and contact with fresh feces would Transportation, Water and Telecommunications still exist (hence a rating of 8). Department. The preceding ranks the health benefits of mainly Kalbermatten, J. M., Julius, D. S. and Gunnerson, C. G. on-site systems. If excreta are transported by cartage or (1982). Appropriate Sanitation Alternatives: A Technical RISKS TO PUBLIC HEALTH 51 Table 3-2. Ranking of exereta disposal technologies by ease of operation and maintenance, water needs, and health benefits (scale of 10) Lack of effort requiredt Healtii benefitsb Water Technology By user By municipality needs Ideal Actual Flush toilet/ sewers/oxidation ponds 10 4 H 10 9 Vault/vacuum truck 8 0 L 8 6 Pit latrine 8 5 L 9 6 Septic tank 6 5 H 8 7 Aquaprivy 5 5 M 9 6 Bucket latrine 3 1 L 5 1 Batch composter (double vault) 1 to L 8 5 Continuous composter (multrum) 0 10 L 7 3 L Low; M medium; H high. a. 0 = maximum effort; 10 = minimum effort. b. 0 = no benefits: 10 = maximum benefits. and Economic Appraisal. World Bank Studies in Water with Ascaris, Trichuris and hookworm. American Journal Supply and Sanitation, 1. Baltimore, Md.: Johns Hopkins of Hygiene, 14, 156-193. University Press. Wagner, E. G. and Lanoix, J. N. (1969). Water Supply for Latham, L., Latham, M. and Basta, S. S. (1977). The Rural Areas and Small Communities. Geneva: World Nutritional and Economic Implications oJ Ascaris Infection Health Organization. in Kenya. World Bank Staff Working Paper no. 271. Winfield, G. F. (1937). Studies on the control of faecal-borne Washington, D.C. diseases in North China. III. Family environmental factors Otto, G. F., Cort, W. W. and Keller, A. E. (1931). affecting the spread of Ascaris lumbricoides in a rural Environmental studies of families in Tennessee infested population. Chinese Medical Journal, 51, 643-658. 4 Detection, Survival, and Removal of Pathogens in the Environment THE COMMENSAL and pathogenic organisms found in concern of water supply engineers was to reduce the human feces-and the environmental characteristics incidence of epidemics of strictly waterborne disease. It of the latter's transmission and control-have been is still an epidemiologically valid testing technique for examined in earlier chapters. The focus of this chapter disinfected water supplies throughout the world, but it is on the suitability of various excreted bacteria as has certain limitations when applied indiscriminately diagnostic organisms to indicate environmental fecal in the examination of wastes and wastewaters, pollution and on the relation of these bacteria to other particularly in hot climates. (These limitations are bacterial and nonbacterial pathogens. In addition to discussed in the section "Relation of Fecal Indicator bacterial indicators, generic "pathogen indicators" are Bacteria to Excreted Pathogens," below.) proposed for assessing the safety of the products of The ideal fecal indicator bacterium should be: excreta treatments. The survival times of indicators and pathogens in different environments (the reader is C A normal member of the intestinal flora of healthy referred to Part Two in this regard) and several issues people affecting the choice of excreta treatment technologies * Exclusively intestinal in habitat, and hence ex- are analyzed in the remainder of the chapter. clusively fecal in origin when found in the environment * Absent from nonhuman animals (a requirement not Fecal Indicator Bacteria met by any of the indicator bacteria currently used) * Present whenever fecal pathogens are present, and Fecal indicator bacteria' are selected from among present only when fecal pathogens might re- those commensal species that exclusively live in the asonably be expected to be present intestinal tract of man and other warm-blooded * Present in higher numbers than fecal pathogens animals without causing disease. Because they are * Unable to grow outside the intestine, with a die-off always and naturally present in feces and are excreted rate slightly less than that of fecal pathogens in large numbers (up to 109 or 1010 cells per gram of * Resistant to natural antagonistic factors and to feces), their presence in water indicates beyond doubt water and waste treatment processes to a degree that the water has been contaminated with fecal equal to or greater than that of fecal pathogens material and possibly with excreted pathogens. If a * Easy to detect and count water is shown to contain fecal indicator bacteria, it is * Nonpathogenic. considered unsafe for human consumption. This is the rationale for the bacteriological testing of public water No one bacterial species or group completely fulfills supplies that was developed in Europe and North all these requirements, but a few come close to doing so. America at the turn of the century when the major Three main groups of bacteria are used as fecal indicators in conventional water bacteriology: the fecal 1. Fecal indicator bacteria are discussed in greater detail in coliforms, the fecal streptococci and the anaerobic chapter 13; see also specific chapters in Part Two for notes on the bacterium Clostridium perfringens. Recently, some taxonomic nomenclature of particular pathogens. other members of the anaerobic intestinal flora, 53 54 HEALTH HAZARDS OF EXCRETA notably Bifidobacterium spp., have been proposed as occurrence has prompted a search in recent years for additional indicator bacteria. Pseudomonas aeruginosa alternative, more satisfactory indicator organisms for has also been proposed, but its status as an intestinal use in hot climates. A further disadvantage of fecal organism is in doubt. An analysis of these bacteria and coliforms is that most standard enumeration pro- their uses as indicators follows. cedures require an accurately controlled incubation period at 440 or 44.5°C, which is difficult to achieve in Coliform bacteria any small, or nonspecialized, laboratory. There are two principal groups of coliform bacteria; the fecal coliforms (comprising mainly the bacterium Fecal streptococci Escherichia coli) and the total coliform group, that includes the fecal coliforms and comprises mainly The fecal streptococci (or Group D streptococci) are species of the genera Citrobacter, Enterobacter, a group of bacteria that are morphologically similar Escherichia, and Klebsiella. The former are exclusively (Gram-positive cocci, measuring approximately 1 fecal in origin, whereas the latter, although commonly micrometer in diameter and occurring in short chains) found in feces also occur naturally in unpolluted soils and are mostly found in the intestines of man and and waters. Of the total coliform organisms found in otherwarm-bloodedanimals.Thegroupincludesspecies fresh feces of warm-blooded animals, generally >90 mainly associated with animals (Streptococcus boutis percent are E. coli, the remainder being species of and S. equinus), other species with a wider distribution Citrobacter, Enterobacter, and Klebsiella (Dufour (for example, S. faecalis and S. faecium, which occur 1977). both in man and other animals), as well as two biotypes Only the fecal coliforms (and especially E. coli) are (S.fraecalis var. liquefaciens and an atypical S. jaecalis definitive indicators of fecal pollution. In water that hydrolyzes starch) that appear to be ubiquitous, bacteriology the total coliforms are regarded as occurring in both polluted and unpolluted environ- "presumptive" indicators of pollution and should be ments. These last two strains, essentially nonfecal absent from disinfected water supplies. In wastewater (although included in the group of fecal streptococci), bacteriology, however, the total coliforms are of are indistinguishable from the true fecal streptococci considerably less importance because many are under routine detection or counting procedures. nonfecal in origin and, especially in hot climates, they Because S. faecalis var. liquefaciens has been reported can multiply in the environment under suitable as the predominant biotype present at low densities conditions, so that their presence or numbers may not (below about 100 fecal streptococci per 100 milliliters; necessarily relate to either the occurrence or degree of Geldreich 1970), the usefulness of the fecal streptococci fecal pollution. In general, and despite the one report group as an indicator is open to question, especially in from India to the contrary (Raghavachari and Iyer clean water bacteriology. Yet fecal streptococci may 1939), only fecal coliforms (or better still, E. coli) still have a place in wastewater bacteriology, although should be used as indicators or tracers of fecal bacterial not as indicators of the bacteriological quality of pathogens in wastes, wastewaters, and treatment and wastewater-irrigated crops, on which the two nonfecal reuse processes. biotypes may both be present as natural flora unrelated Fecal and total coliforms are indistinguishable to the degree of fecal pollution. There is no under the microscope: they are all Gram-negative rods information, however, on the distribution of these two measuring some 2-5 by 0.4 micrometers. In practice biotypes in tropical environments. they are differentiated by the ability of fecal coliforms Aside from the possible problem of nonfecal strains (mainly E. coli and thermotolerant K. pneumoniae) to of Group D streptococci, fecal streptococci have major ferment lactose with the production of acid and gas advantages as fecal indicators. They are enumerated by within 24 to 48 hours at a temeprature of 44°C. In a single-step membrane-filter procedure at 37°C, a addition, the most common fecal coliform, E. coli, can temperature readily attained in small field labora- produce indole from the amino acid tryptophan at this tories. They are less prone to regrowth, and generally temperature. In hot climates, however, some nonfecal survive somewhat longer, than fecal coliforms and may coliforms can grow at 44°C and some can also produce thus be better indicators of excreted bacterial indole at this temperature, thus mimicking the fecal pathogens (that have little regrowth tendency) and coliforms (E. coli in particular). There are no excreted virus (that survive for longer than fecal satisfactory routine methods for differentiating be- coliforms in cool waters). These points are discussed in tween these organisms, and their simultaneous greater detail in chapter 13. DETECTION, SURVIVAL. AND REMOVAL OF PATHOGENS 55 Fecal coliform tofecal streptococci ratio length by 1-2 micrometers in width. It is exclusively It has been found that human feces in the USA fecal in origin and is also pathogenic, causing gas contain at least 4 times as many fecal coliforms as fecal gangrene and food poisoning (Chakrabarty, Narayan and Chandiramani 1977). Because it is a spore-forming times . streptococci,t a fec ai atleas.4 organism, it can persist for long periods outside the times as many fecal streptococci as fecal cohiforms inetn,adteeoecnb sda nidctro (Geldreich 1966). It was therefore suggested that intestine, and therefore can be used as an indicator of American surface waters that have fecal coliform- occaslional or watermittent polluthonp or of previous streptococci ratios of > 4 are likely to have received pollution of waters In which the presence of neither streptococinrantiosh pof ll4tare,likelyet thae receivd fecal coliforms nor fecal streptococci can be demon- ratios of <0m 7 mainly have been contaminated by the strated (Bisson and Cabelli 1980; Cabelli 1977). C. raio of <0. manyhv.encotmntdbh pe7:fringe71s iS also more resistant than both fecal feces of wild and domestic animals (Geldreich 1966). . r . . . This method, however, is of no value in practice. The coliforms and fecal streptococci to antagonistic ' ' . . . ~~~~~~substances such as chlorine. fecal coliform-streptococci ratios in fresh feces vary widely in different animal species and geographical In wastewater bacteriology, however, its long persistence is a disadvantage because residual, locations. It is not true that humans the world over dormant populations of the bacterium in waters may excrete a ratio of >4, and animals <0.7 (Wheater, nor reflect the true degree of pathogenic contamin- Mara and Oragui 1979). Once the feces have been ation. Type A C. perfringens from human feces may excreted, the ratios will change because of the also grow in the soil (in contrast to other types of C. differential death rates of the various bacteria. The .g . . enterococci (S. flaecalis, S. faecium, and S. dur-ans) perrilngens of anm.al origin, which seem to die-out in typically survive longer than fecal coliforms which in soil). turn survive longer than S. bovis and S. equinus (McFeters and others 1974). It was therefore suggested Pseudlomonas aerugi72osa that for human pollution, in which enterococci are the The organism is an opportunistic human dominant fecal streptococcal species, fecal.coliform- pathogen that causes infection in wounds (especially streptococci ratios in water samples returned to the burns) and also ear and urinary tract infections, laboratory will fall; whereas for animal pollution, m a o n which S. bovis or S. equinus may be more numerous, the meigts'eprtr netosadohrcniin whics. iorstor s.pes may be morem numerut (Cross 1979). It is often associated with sepsis in ratios in stored samples may rise (Feachem 1975). But ohriedblttdptet nhsia ad.P it nw apearsthat wheeas ntercocc arethe otherwise debilitated patients in hospital wards. P. domitnow aecars that,cweralspenteroin har the aeruginosa is being increasingly implicated as a cause dominant fecal streptococcal species in humans inoma neto n knrs olwn xouei developed countries (and therefore human pollution is of ear yfectlion and skm rash followlng exposure l associated with falling ratios), enterococci can also be poolebaths (cson,eHoad and Fam r17 the dominant fecal streptococcal species in some McCausland and Cox 1975 Seyfried and Fraser 1978; animals (for instance, cats, ducks, hens, mice, pigs, Waushund and Cot 1976). rabbits, rats, and seagulls in Scotland; Wheater, Mara and Oragui 1979). Furthermore, S. equinus and S. bovis P. aeruginosa is a Gram-negative, aerobic, nonspor- are common in the feces of people in some countries ulating rod measuring approximately 0.5 by 2 micro- meters. It occurs, normally at low concentrations of (for intance, India and Uganda; Drasar and Hill 1974). abu 50ognssprga,intefcso' ml It may be concluded, therefore, that neither the ratio at about 50 organisms per gram m the feces of a small the time of sampling, nor the change in ratio in a stored proportion (about 3 to 15 percent) of healthy people. It sample, conveys useful information about the origins of probably does not grow in the intestine of healthy fecal pollution. The development of a routine test to people, and P. aeruginosa isolated in feces may be fectiolutio Th developmen t ofea rounetest survivors of ingested bacteria. Studies in which P. dstiongisthe human from nonhma f.earctin aeruginosa was fed to volunteers demonstrated that sation miscthe bighest currentpriort y fo r ragesearc i large numbers (Ž, 106) must be ingested to produce fecal carriage, which did not persist for more than 6 days (Buck and Cooke 1969). Closti-idiur/t pe7yi-ingenis P. aeruginosa is common in sink traps and flower water. It has been reported in fairly high concentra- The bacterium Clostridiuni perfi ingens (formerly C. tions (> 103 per 100 milliliters) in urban stormwater welchii) is anaerobic, spore-forming, Gram-positive, runoff in Canada (Qureshi and Dutka 1979), and in and measures approximately 4-6 micrometers in higher concentration in sewage (> 105 per 100 56 HEALTH HAZARDS OF EXCRETA milliliters) and hospital sewage (> 106 per 100 Fecal concentrationis, detection, andl enumeration qJ milliliters) in Scotland (Wheatcr and othcrs 1980). It bacterial indicators has been suggested (Cabelli, Kennedy and Levin 1976) that a consideration of P. aerugittosa-E. coli ratios in Approxlmate numbers of indicator bacteria co4 - fecally contaminated waters can provide evidence on monly found in human feces are given in table 4-1. The the possible origins of the pollution, with coun cell counts in the table are average figures only and >100fecal coliforms and < 1 P. alerulginlosa per 100 are mainly derived from American literature. Some 1lt,000 fers being and p.ttieithganima communities, because of dietary differences (see table milliliters being associated putatively with animal. 1-6), may display considerably different numbers for rather than human, pollution. But P. aeruginosa occurs rathe than human, pollution. ButP . aeruginosaoone or more of the listed indicators (see also chapter widely (albeit in highly variable numbers) in nature as a 13) free-living organism (Green and others 1975; Parker 13). e 1 r ^ r ~~~~~~Methods suitable for the detection and enumeration 1971); it can therefore have little usefulness in studies of of coliform bacteria, fecal streptococci, and C. fecal contamination. pefrfingens are described in the 15th edition of Standard Methods for the Examination oJ Waters and Bt ,1..4., and other anaterobic bacteria Wastewvaters (American Public Health Association Bifidobacteria (previously known as anaerobic 1980) and in the 4th edition of The Bacteriological E.xamination oJ Water Supplies (Department of Health lactobacilli) are nonsporulating, anaerobic organisms andnSoiety Ser 1969). A membrane-filter that occur in the intestines of man and other animals: they areGram-positiveV- orY-shapedcells, with each technique for enumerating C. peirringens is also branch measurinabu 0b to 4 cetes. the described by Bisson and Cabelli (1979). P. aeruginosa branch marnat. T populations can be counted by membrane filtration most common species in man are Br, .i.l;,; :rnum? adolescent ismand B.s in gum.nar BiFidobacteriauhave using the medium of Levin and Cabelli (1972) rdolescently beenp d as lnindic. ator anisms frue supplemented with 0.1 percent cetrimide (Wheater and recently been proposed as indicator organisms for use ohr 90 e loBosyadCei 98 uk in topial wter becusethelactose-fermenting others 1980; see also Brodsky and Ciebin 1978; Dutka in tropical waters because the r and Kwan 1977; Hoadley 1977). The membrane species are exclusively fecal in origin (Cabelli 1978; . filtration method and medium for Bfifdobacterium spp. Levin 1977). Thev therefore overcome the principal are described by Evison and Morgan (1978), but no disadvantage of fecal coliform counts on tropical satisfactory routine procedure for enumerating these samples that such samples may contain a significant bacteria has yet been developed. Reference may also be proportion of strains that can ferment lactose and made to Mara (1974). FsSee note on page 66.] produce indole at 44°C but do not derive from feces. An additional advantage of bifidobacteria is that, because they are strict anaerobes and grow poorly below 30°C, Relation of Fecal Indicator Bacteria to they have very low multiplication potential in Excreted Pathogens extraintestinal environments. Work on bifidobacteria has only commenced relatively recentlv. and there is little informatin on tFecal indicator bacteria were originally identified to littleinvironments ot thanrsurviva in ri w terainesoinand assess the bacteriological quality of potable waters at a Morganm1978) other than in riverwater Evisonand time when only the transmission of bacterial Morgan 1978). The bacterial flora of feces is predominantly composed of anaerobic bacteria (table 1-6). Bifido- Table 4-1. Number oj indicator bacterica commonlv bacteria have been described, but feces contain large fiund in humanjeces numbers of other nonsporulating anaerobes. such as Bacteroides spp. (commonly B. j a ,i , the anaerobic Cells per grain oj fece.s Gram-positive cocci (Peptoccus spp. and Peptostrepto- Incdicu tor (xwet weight) coccus spp.) and Eubacterium spp. Current research is investigating the usefulness of these organisms as fecal BuctreoidIes spp. lo--lo, indicators, but at present there are insufficient data on Bifidobacterhion spp. 10- 10'' their extraintestinal ecology to know whether or not Clostridiun, pertrin,gen7S 103_01") use of all or some of them as indicators will be Coliforms Fecal 106-0o, practicable. Moreover. current techniques for their Nonfecal t0-109 detection and enumeration are rather complex for Fecal streptococci V510-1 routine use. DETECTION, SURVIVAL, AND REMOVAL OF PATHOGENS 57 enteropathogens (such as salmonellae, shigellae, and pathogens are considered, the bacterial fecal indicators cholera vibrios) was considered the major public are of limited usefulness. They are of some use in health risk from drinking water. Historically (and to assessing the quality and resulting risks to health of some extent, even now), attention has therefore focused irrigation waters, but even here the gaps in knowledge on the relation of the fecal indicators to bacterial are considerable. Much of the existing information on pathogens. Recent literature, continuing this emphasis, the relation of fecal indicators and excreted pathogens contains many reports on the persistence of fecal comes from relatively wealthy communities (for coliforrms and salmonellae in the extraintestinal example North America, South Africa, and Israel), and environment, but only a few reports on the these data cannot be applied with much confidence to comparative survival of the fecal indicators and other communities in which climate, diet, disease nonbacterial fecal pathogens (such as viruses, pro- patterns, agricultural practice and cultural attitudes to tozoal cysts, and helminth eggs). This has partly been a excreta reuse products are all different. This does not result of the difficulty of routinely analyzing samples mean that information on, say, fecal coliform survival for these other pathogens (especially viruses), but an in Israel cannot be used to predict fecal coliform uncritical acceptance of the historical direction of survival in, say, rural India but it does mean that the research in the field has also contributed to the neglect. information may not be all that relevant to conditions Thus, for example, there has been no report on the in rural India, where the ability to make statements relation of the indicator bacterium C. perfringens and about fecal coliform survival may not help assess the the eggs of the fecal helminth Ascaris lumbricoides degree of fecal pathogen contamination of crops (both persist for longer periods in the extraintestinal irrigated with sewage effluent or fertilized with treated environment than do other organisms of their excreta. Caution must therefore be exercised in respective kind). Knowledge of such a relation would applying data on fecal indicator survival in environ- be of little value in assessing the safety of urban water ments other than those from which the information supplies (in which Ascaris eggs are not a public health was obtained. hazard) but it might be of assistance in assessing the In summary, little is known about the relative quality of sewage sludges, composted feces, and some concentrations of indicator bacteria and bacterial wastewater effluents. pathogens in effluents and fecal products in warm This one example illustrates the longstanding climates and practically no information exists on the preoccupation of sanitary bacteriologists with urban relative concentrations of indicator bacteria and water supplies to the near exclusion of appropriate nonbacterial pathogens. In addition, it must be noted consideration of wastes and wastewaters, and of the that the stability of the ratio between the concentration comparative removal and persistence of fecal pa- of an indicator bacteria and the concentration of a thogens and indicator bacteria in treatment processes particular pathogen decreases as the size of the and reuse products. There are many data (mainly from contributing population decreases. Thus, for systems North America and admittedly of variable quality) on serving small communities, or for individual systems the relation between the survival ofbacterial pathogens such as aquaprivies or composting toilets, the ratios and indicators in sewage treatment processes in will vary enormously from place to place and from time temperate climates, but very little data from tropical to time, and no organism will act as a good indicator of countries. Predicting with confidence the likely density another organism. of salmonellae in a tropical sewage effluent, even when the number of fecal coliforms present is known, is extremely difficult; in contrast, reasonable estimates Pathogen Indicators are possible with a temperate climate effluent. This neglect makes the establishment of a fecal coliform Fecal indicator bacteria only demonstrate fecal standard for most tropical sewage effluents a highly contamination. This fact is useful in assessing the safety unscientific process. Because engineers design, for of drinking water supplies, but when the health aspects example, maturation pond systems on the basis of fecal of sanitation systems, excreta and sewage treatments coliform removal to the desired standard, this state of and reuse processes are considered, what is needed is scientific uncertainty can lead to either overdesign not a fecal indicator bacterium (for feces are obviously (with a consequent unnecessary increase in cost) or present) but, rather, a pathogen indicator organism. A underdesign (with a consequent increased risk, and reliable measure ofthe total pathogen content ofthe end perhaps actual damage, to public health). product of a treatment process is needed, so that the When the hazards from nonbacterial excreted health risks associated with any reuse of the end 58 HEALTH HAZARDS OF EXCRETA product, or with its discharge into the environment, can fecal coliforms and fecal streptococci are perhaps the be gauged as accurately as possible. If these risks can be best pathogen indicators. It is difficult to determine judged, responsible and informed decisions can be what density of fecal coliforms or fecal streptococci- made-for instance, on whether the benefits from end- as an indication of the presence of endemic product reuse outweigh the possible health costs and pathogens should be permissible. The rather unhelp- whether further treatment is necessary to protect the ful answer is that the densities should be as low as health of those involved (either as producers or possible, which in practice means at least below 1,000 consumers) in the reuse process or, in the case ofthe end per 100 milliliters of effluent (and preferably below 100 products being discharged into the environment, of the per 100 milliliters). Effluents reused for the irrigation of users of the environment. crops that may be consumed raw must have fecal It would be unrealistic to expect the same pathogen coliform and fecal streptococci counts that are both indicator organism to be useful in assessing the below 100 per 100 milliliters. Viral and bacterial pathogen content of different kinds of fecal products pathogens may or may not be absent at these indicator for example, composted feces and the effluent from organism densities, but in general health risks will be waste stabilization ponds. In the former case the so minimal that further treatment will not normally be concern is primarily the viability of the persistent economic. helminth eggs (notably Ascaris Itlmbricoides eggs) whereas in the latter case it is known that, if the total .. . . ~~~~~~Pathogeii indicatorsfor , ni-,, -;i fi-om other sewzage retention time in a stabilization pond system is more Pathenir than 20 days, the effluent will be free of both helminth treatments eggs and larvae but may contain excreted viruses and The effluents produced by sewage treatment bacteria. Because of these variations, it is convenient to processes other than waste stabilization ponds are divide fecal products into two groups, effluents and likely to contain a full range of fecal pathogens- noneffluents, and to examine which organisms are viruses, bacteria, protozoal cysts, and helminth eggs. suitable pathogen indicators for each. There is no suitable fecal indicator organism in these circumstances; it is not possible to have a single organ- Pathogen indicatorsj. r pond ism indicate the presence of so diverse a group of pathogens. Fecal coliforms have been used, but only for The effluents from waste stabilization ponds and historical reasons (they are totally inappropriate other sewage treatment processes are best considered indicators for the helminth eggs for instance). This separately because the vastly different retention times subsection can conclude with the generalization that if involved (weeks in ponds, hours or days in other a sound economic argument can be put forward for the processes) produce effluents with markedly different use of treatment processes other than ponds, then the pathogen contents. If a pond system has a retention effluent from such treatments should undergo tertiary time of more than 20 days its effluent will be free from treatment or be heavily disinfected or discharged well both pathogenic protozoa and helminth eggs and out to sea because, in the tropics, the health risks from larvae, but it may still contain viral and bacterial the effluent may be similar to those from raw sewage. It pathogens. Because a routine analysis of pond effluents should be noted that heavy disinfection is often for pathogenic viruses and bacteria is not yet feasible ineffective (especially against viruses and helminth (nor likely to become so in the immediate future), the eggs) and has undesirable environmental con- choice of a suitable pathogen indicator is exceedingly sequences. difficult. Bacteriophages--and more specifically, coli- phages--may provide a solution in the future but the Pathogen indicators.]br laboratory techniques are not yet widely known. Fecal coliforms or fecal streptococci would seem an obvious Noneffluents are taken here to include night soil, the choice, but there is little data on the usefulness of either contents of pit latrines and composting toilets and the as viral indicators, and the literature on their respective sludges from aquaprivies, septic tanks and con- survival compared to pathogenic bacteria is only ventional sewage treatment works. It is reasonable to slightly less scant (especially for tropical pond assume that, if ascariasis is endemic and there are no effluents). There is no information available on the viable Ascaris eggs present in the wastes analyzed, then usefulness of bifidobacteria and the other non- sporulating anaerobes. 2. Effluent disinfection is discussed further in chapters 6,9, 13, and Although they are less than ideal for the purpose, 23. DETECTION, SURVIVAL, AND REMOVAL OF PATHOGENS 59 other pathogens are absent as well, since Ascaris eggs environmental condition likely found in a night soil or are so resistant. Thus, and in the current absence of any sewage treatment system that is highly fatal to all data on the comparative survival of the bacterium C. pathogens in a reasonably short time (a few hours) is perfringens, the viable eggs of Ascaris lumbricoides raised temperature (in the range 55-65°C). The only would appear to be the best pathogen indicator other low-cost process that causes 100 percent removal currently available for noneffluents. This indicator has or destruction of most pathogens is the waste been accepted in China, where standards of 95 percent stabilization pond system with its long retention times, Ascaris egg mortality have been adopted for the exposure to sunlight, and good sedimentation proper- agricultural reuse of excreta (McGarry and Stainforth ties. 1978). The elapse of time is a feature common to all treatment, disposal and reuse technologies; in many cases, it is the feature that most determines the Survival of Indicators and Pathogens pathogen removal achieved. The rate of loss of infectivity of an organism also depends very much on From the time of excretion, the concentration of all temperature; most organisms survive well at low pathogens usually declines from the death or loss of temperatures (; 5°C) and rapidly die at high infectivity of a proportion of the organisms. Viruses temperatures (>40°C). Except in sludge or night soil and protozoa will always decrease in numbers digestion processes, temperatures approximate following excretion, but bacteria may multiply if they environmental temperatures-in most developing find themselves in a suitably nutrient-rich environment countries, generally in the range of 1 5-350C and with a minimum of competition from other micro- commonly of 20-30°C. It is therefore useful to know organisms. This can occur when salmonellae, for the persistence of pathogens at ambient temperatures instance, contaminate certain foods, or when E. coli in different environments so that the likely pathogen multiply in a chlorinated sewage effluent from which content of various fecal products can be predicted. In many other bacteria have been eliminated. Multi- this section pathogen survival at ambient temperatures plication of bacterial pathogens is generally rare, is reviewed with the following considered in turn: however, and is unlikely to continue for very long. survival in feces, night soil and sludge; survival in water Intestinal helminths-except the trematodes, which and sewage; survival in soil; and survival on crops. have a multiplication phase in their molluscan Under each heading that follows, the available intermediate hosts-will decrease in numbers follow- knowledge is summarized as succinctly as possible. A ing excretion. The multiplication possibilities for the greal deal of additional information is given in Part excreted pathogens were summarized in table 2-3. Two and some of the data are further tabulated in The ability of an excreted organism to survive is Feachem and others (1980). defined as its persistence (discussed in chapter 2). The The shape of the curve describing pathogen survival natural death of organisms when exposed to a hostile over time should determine the way in which survival is environment is of the utmost importance because it reported. Many bacterial populations decline expo- reduces the infectivity of excreta independently of any nentially, so that 90 or 99 percent of the bacteria are treatment process. In fact, some treatment processes lost relatively quickly with a few organisms persisting have little effect on excreted pathogens and simply for longer periods. Such a situation is best described by allow the necessary time for natural die-off to occur. the probability of survival for a given time or by half The effect of conventional sewage treatment on life, the time required for half the population to die. For protozoal cysts is of this kind (see chapter 20). Certain instance, 50 percent of fecal coliforms may die in 20 treatment processes, however, create conditions that hours in water, whereas a few may persist for up to 50 are particularly hostile to excreted pathogens and that days, and the results obtained will depend heavily on promote their rapid death. The effects of activated sampling procedures. Most of the literature gives data sludge on fecal bacteria, or of thermophilic digestion on the persistence of the small proportion of long-term on all organisms, are of this kind. The essential survivors and only a few authors have reported the environmental factors in limiting pathogen persistence shape of the death curve or given the 50 to 90 percent are time and temperature. The success of a given destruction times. The discussion below will therefore treatment process in reducing the pathogenicity of an mainly concern the overall persistence of a few effluent or sludge thus depends, in general, upon its organisms. This focus is epidemiologically appropriate retention time and its creation of an environment for organisms that can replenish their numbers if they especially hostile to particular organisms. The sole find themselves on food or other suitable substrates 60 HEALTH HAZARDS OF EXCRETA (for example shigellae, salmonellae and pathogenic E. are summarized in table 4-3. For all organisms survival coli) or for organisms whose infective dose is believed is highly dependent on temperature, with greatly to be low (the excreted viruses, for example). It is less increased persistence at lower temperatures. Survival appropriate for cases in which regrowth is unlikely and of bacteria is also highly dependent on the presence of infective doses may be high (for example, Vibrio other microorganisms in the water that might provide cholerae); in these cases it is the rapid decline of the competition or predation. Bacteria often survive bacteria to a level that no longer presents a major longer in clean water than in dirty water and the public health hazard that is important. In organisms longest survival times are obtained by inoculating a having several developmental stages outside the single bacterial species into sterilized polluted water. human host (such as hookworms and schistosomes), There is some evidence that virus survival is enhanced each stage will have its own separate survival pattern. in polluted waters, presumably a result of some When a developmental stage is actively moving yet protective effect that the viruses may receive when they dependent on an unreplenished energy source (for are adsorbed onto solid particles in dirty water (see example, the schistosome miracidium seeking its snail chapter 9). Coliforms, in particular E. coli, have host) the length of life may be precisely defined. attracted the most interest because of their established role as indicator bacteria. Substantial regrowth of coliforms is possible in organically polluted waters, but In fe?ces, night soil, and sludge this growth phase will give way to a progressive die-off. There is less literature on the survival of pathogens in Survival in excess of 50 days is most unlikely and, at these media than in the aqueous environments 20-30°C, 20 days is a more likely maximum survival discussed in the following subsection. Some sources time. Mixed fecal streptococci have a similar (perhaps a refer to survival of pathogens in sewage works' sludges, little longer) survival but, if the streptococci are but survival in feces and night soil may be assumed to predominantly S. bovis or S. equinus, the survival times be broadly similar. Research on pathogen survival in are substantially shorter (see chapter 13). aiim- "di these media may be summarized as shown in table 4-2.' survival has also been widely reported. Survival of over 2 months has been recorded, but 1 month is a more common upper limit (see chapter 15). Shigella spp. and In wrater and seusage Many studies on the survival of excreted organisms Table 4-3. Survival times of excreted pathogens in in water and sewage have been conducted.' The data fresh water and sewage at 20-30'C Table 4-2. SUtrvivcal times of excreted pathogens in feces. night soil, and sluidge at 20-30oC Survoival time ____________________'_________ Pathogen (days) Survival time Virusesa Pathogen (days) Enteroviruses' < 120 but usually <50 Viruses Bacteria EVterovirusses < I 00 but usually < 20 Fecal coliformsa <60 but usually <30 Salnmonella spp.a < 60 but usually <30 Bacteria Shigella spp.3 <30 but usually <10 Fecal coliforms <90 but usually <50 Vibrio choleraec <30 but usually <10 Salmonella spp. <60 but usually < 30 Protozoa -_= ,. spp. <30 but usually <10 EntaPoebahistolvocacysts <30butusually <15 liibrio cholerae <30 but usually <5 Protozoa Helminths 1l ~~~~Ascaris lumbricoides eggs Many months Enrtamoeba histoltrica cysts <30 but usually <15 Helminths a. In seawater, viral survival is less, and bacterial survival is very Ascaris lumbricoides eggs Many months much less, than in fresh water. b. Includes polio-, echo-, and coxsackieviruses. a. Includes polio-, echo-, and coxsackieviruses. c. 1V cholerae survival in aqueous environments is a subject of current uncertainty-see chapter 17. 3. A compilation of original sources and findings on survival in feces, night soil, and sludge can be found in the appropriate sections 4. These studies are reviewed in the appropriate sections of Part of Part Two. chapters 9 through 35. Two, chapters 9 through 35. DETECTION, SURVIVAL, AND REMOVAL OF PATHOGENS 61 Vibrio cholerae are less persistent, and survival of these Table 4-4. Factors affecting survival time of enteric bacteria for more than 20 days is seldom reported (see bacteria in soil chapters 16 and 17). The development of viral detection techniques in the Soiljactor I u_, oni bacterial surcival 1950s led to the demonstration of the presence of excreted viruses in the environment. The enteroviruses Antagonism from soil (polio-, coxsackie-, and echoviruses) have been microflora Increased survival time in sterile soil frequently isolated from water and wastewater Moisture content Greater survival time in moist soils and (chapter 9) and the literature on this subject is growing during times of high rainfal (chaptery 9) Moisture-holding Survival time is less in sandy soils than rap1dly at the present tzme. V1ral surv-1val may oe capacity in soils with greater water-holding longer than bacterial survival and it is greatly increased capacity at lower temperatures. In the 20-30'C range, 2 months Organic matter Increased survival and possible re- seems a typical survival time, whereas at around 10'C, growth when sufficient amounts of 9 months is a more realistic figure. organic matter are present 9mns1amrratcfuepH Shorter survival time in acid soils Protozoal cysts are poor survivors in any environ- (pH 3-5) than in alkaline soils ment. A likely maximum for Entamoeba histolvtica in Sunlight Shorter survival time at soil surface sewage or polluted water is about 20 days (see chapter Temperature Longer survival at low temperatures: 20). Helminth eggs vary from the very fragile to the very longer survival in winter than in persistent. The most persistent of all are Ascaris eggs, summer which may survive for a year or more (see chapter 23). Source: Adapted from Gerba. Wallis and Melnick (1975). In soil but Ascaris eggs can survive for several years (see Survival times in soil are relevant in all situations chapter 23). The situation is summarized in table 4-5. where effluent, sludge, compost, or other fecal products are being applied to the land as fertilizers or soil conditioners.5 Several factors, shown in table 4-4, affect On crops the survival time of enteric bacteria in soil (Gerba, Excreted viruses and bacteria cannot penetrate Wallis and Melnick 1975). Fecal coliforms can survive undamaged vegetable skins. However, there are many for many months under optimal conditions. In warm reports in the literature on the isolation of all kinds of climates, especially when arid, survival is limited to 2-3 excreted pathogens from the surface of vegetables that months at most. Fecal streptococcal survival is likely to have been irrigated or fertilized with fecal products.6 be longer if human enterococcal species are dominant Root vegetables are more prone to contamination than (see chapter 13). Survival of salmonellae may be up to 1 others. Weather conditions have an important year if the soil is cool, moist and rich in organics (for example, if it is fertilized), but strain variation is Table 4-5. Survival times of excreted pathogens in considerable and 50 days would be a more typical soil at 20-30°C maximum (see chapter 15). Data on NhŽliy,ul or Vibrio cholerae survival in soil are limited (see chapters 16 and Survival time 17). Pathogeni (days) The information available on viruses suggests that virus particles adsorb to soil particles and become Viruses protected from environmental factors. Viral survival is Enterovirusesa < 100 but usually < 20 greater at low temperatures: survivals of up to around Bacteria 3 months have been reported in warm weather, Fecal coliforms <70 but usually <20 increasing to around 5 months in European winter Salmonella spp. <70 but usually <20 conditions (see chapter 9). Protozoal cysts in soil are Vibrio cholerae <20 but usually <10 most unlikely to survive for more than 10 days (see Protozoa chapter 20). Helminth egg survival varies enormously, Entamoeba histolytica cysts <20 but usually < 10 Helminths 5. A comprehensive review of the persistence of excreted Ascaris lumbricoides eggs Many months pathogens in soil is contained in the appropriate sections of Part Two, chapters 9 through 35. a. Includes polio-, echo-, and coxsackieviruses. 62 HEALTH HAZARDS OF EXCRETA influence on the survival of pathogens on plants; The emphasis in the literature on the exact warmth, sunshine, and low air humidity greatly proportions of pathogens removed by various treat- promote pathogen death. The survival characteristics ment processes is thus misleading. For instance, most of various excreted organisms on crops may be conventional treatment plants remove 90 to 99 percent summarized as shown in table 4-6. As indicated in the of enteric bacteria.' This is a very poor removal; table, pathogen survival times on vegetables are short whether trickling filters remove a little less (say 95 compared to survivals in other environments. percent) than activated sludge plants (say 99 percent), Protozoal cysts are rapidly killed. Viruses, bacteria, they are both technologies with poor pathogen and worm eggs survive for longer, but little survival of removal characteristics (but they were never designed any species is to be expected after 2 months. to have them-see the next section). A removal ability of less than 99 percent means always more than 1 percent survival, or always less than a log unit Pathogen Survival versus Removal in reduction of 2. In developing countries, where Waste Treatment incoming wastes have high concentrations of pa- thogens (especially viruses, bacteria, and protozoal Pathogen survival, rather than pathogen removal, is cysts-see table 1-10), a survival of more than 1 percent purposely referred to in this book. This is because is usually inadequate. health hazards are posed by the pathogens that survive In considering treatment technologies by their a treatment process, not by those that are removed by ability to remove pathogens, it is necessary not to dwell treatment. Figures such as 99 percent or 99.9 percent on trivial differences (for instance, 92.3 percent versus removal appear highly impressive but they represent 1 97.8 percent removal), but to translate removal or 0.1 percent survival, respectively, and this degree of efficiencies into orders of magnitude. Conventional survival may be highly significant wherever incoming treatment works remove between 1 and 2 log units of concentrations are great. If an influent to a sewage enteric bacteria and should be contrasted with works contains, say, 105 pathogenic bacteria per liter, technologies, such as waste stabilization ponds, which then 99 percent removal will produce an effluent with remove 5 log units. In considering stabilization ponds 103 pathogenic bacteria per liter. In areas where the or thermophilic digesters, which have high removal effluent is to be reused, or where it is to be discharged to performances, it is also misleading to talk in terms of a stream that populations downstream use as a source percentage removal (use of this convention disguises, of drinking water, such effluent quality may be for instance, the important difference between 99.99 inadequate. and 99.999 percent removal). The removal characteristics of treatment techno- Table 4-6. Survival times of excreted patihogens on logies should be related to the incoming con- crops at 20-30°C centrations of particular pathogens, to the intended reuse or disposal arrangements, and to the associated Survival time health risks. Different pathogens occur in varying Pathogen (days) concentrations and are affected in different ways by a given treatment technology. For instance, protozoal Viruses cysts will be found in raw sludge in relatively low Enterovirusesa <60 but usually <15 numbers and will not survive sludge treatment. In Bacteria contrast, Ascaris eggs may be found in sludge in high Fecal coliforms <30 but usually <15 concentrations and will survive most sludge treatment Salmonella spp. <30 but usually <15 processes. s... .: . spp. < 10 but usually < 5 Vibrio cholerae <5 but usually <2 Protozoa Objectives of Night Soil and Sewage Entamoeba hsistolNtica cysts <10 but usually <2 Treatments Helminths The primary objective in the treatment of night soil or sewage from communities in which excreted infections are endemic is the destruction of excreted a. Includes polio-, echo-, and coxsackieviruses. 7. The processes that conventional sewage treatment comprises. 6. These reports are reviewed in the appropriate sections of Part and their ability to remove various excreted pathogens, are discussed Two, chapters 9 through 35. in chapter 6 and reviewed at length in the chapters of Part Two. DETECTION, SURVIVAL, AND REMOVAL OF PATHOGENS 63 pathogens. This is principally achieved by a com- excreted pathogens will be present (see table 5-1). bination of time and temperature, although other Composting toilets thus have definite health risks that, conditions of the extraintestinal environment are also although slight, should be recognized by the designers important (for example, sunlight and oxygen availab- and users of these systems. In strictly economic terms ility). From the extensive literature review in part 2, it the value of the compost must be greater than the appears that no excreted pathogen-with the excep- possible cost to health from its use. tion of spore-forming bacteria (for example C. The health hazards associated with the collection of perfringens) and possibly hepatitis A virus-can night soil from bucket and vault latrines are described survive a temperature of more than 65°C for a few in the section "Cartage Systems" in the next chapter. If minutes. As the temperature falls survival increases; urine is collected as well as feces, the night soil is a fecal thus, at 10°C, for instance, Ascaris eggs may survive for suspension similar to primary sewage sludge and may several years, enteroviruses for 12 months, and be treated by mesophilic or thermophilic digestion. It shigellae for 2-3 months. also may be treated in a pond system which can be The degree to which night soil and sewage are designed to produce little effluent so that very long treated is largely influenced by what is to be done with retention times are possible (> 1 year) and, con- the sludge, compost or sewage effluent.8 It is thus sequently, no survival of excreted pathogens. If the accepted engineering practice to discharge untreated urine is not collected, or is allowed to drain away, the sewage into the sea, provided that the outfall is night soil (now principally feces) may be disposed of, designed to ensure that no pollution of beaches or treated, and reused in a number of ways (see also the shellfish-growing areas will occur; but if reuse of an section "Composting" in chapter 5). Night soil cartage effluent for the irrigation of edible crops is intended, the and treatment systems will tend to have higher health designer's goal should be the absence of excreted risks than many other systems, although risks can be pathogens on the surface of crops, and he should greatly reduced by the use of modern methods (such as accordingly design the treatment works for a very low those found in Japan). In high-density urban settings, degree of pathogen survival. where the only technological alternative may be a sewerage system, cartage systems will often be economically attractive despite their health hazards. In other settings, where a greater range of technologies The effectiveness of treatment methods for excreta is feasible, cartage may be less attractive. and night soil depends greatly upon their time- temperature characteristics. The effective processes are Sewage treatment those that retain the excreta for a long time (> 1 year), or make it warm (>55°C), or effectively combine Those whose job is to select and design appropriate adequate retention time and high temperature. systems for the collection and treatment of sewage in Pit latrines (see the section of that title in the next developing countries must bear in mind that European chapter) have a useful life of a few years; when one and North American practices do not represent the becomes full, a second is dug, and the contents of the zenith of scientific achievement, nor are they the first are left undisturbed while the second is in use. product of a logical and rational design process. Because of the time interval there are no health hazards Rather, treatment practices in the developed countries associated with digging out the contents of previously are the product of history, a history that started about filled and covered pit latrines. Provided the squatting 100 years ago when little was known about the plate is regularly cleaned, pit latrines pose no greater fundamental physics and chemistry of the subject and risks to health than do flush toilets (though insect when practically no applicable microbiology had been breeding can be a serious problem-see chapters 36 discovered. Only since 1970 have the tools to do serious and 37 and odor can be a nuisance). work in water and wastewater virology been Composting toilets (see the section of that title in the developed, and only since 1975 have the roles of next chapter) are of two types: batch and continuous. If rotavirus, Campylobacter, and E. coli9 in the etiology of the composting period is over 1 year, only a few Ascaris diarrheas been demonstrated. eggs will be present in the product. With composting periods of under 1 year, varying numbers of other 9. The epidemiology of infections with rotavirus, Campylobacter, 8. Treatment strategies for different reuse and disposal practices and pathogenic E. coli are reviewed in chapters 11, 12, and 13, are discussed in chapter 7. respectively. 64 HEALTH HAZARDS OF EXCRETA The historical development of European and North 35°C, allow high pathogen survivals, and the full range American sewerage systems can be roughly summar- of excreted pathogens present in the raw sewage ized as follows: appears in the effluent. The sludges produced in conventional sewage works and oxidation ditches also .. A n e fcontain the full range of excreted pathogens and An the consequentisks to hualor the l.e .to e require some form of treatment before disposal or and the consequent risks to health ledt to the rue reuse. construction of sewers that discharged raw wastes Conventional sewage works were originally de- into rivers (in the mid-nineteenth century in veloped in order to prevent gross organic pollution in London, for instance). European and North American rivers; they were never * This discharge of raw wastes yielded massive intended to achieve high removal of excreted pollution and oxygen depletion in the rivers, which pathogens. Their use in tropical countries in which often became foul, open sewers. excreted infections are endemic is only justifiable in Varousce te s echnologes were developede special circumstances, for there is an alternative reduc the suspended load and the oxygen demand treatment process much superior in obtaining low of the discharged wastes (for example, the UK Royal s o e Cmiso on Seag Dipoal, 189195 survivals of excreted pathogens-the waste stabiliz- Commission~~~~~~ ~ on Seag Dipsl'19 95 ation pond system."1 Retention times commonly proposed effluent standards of < 30 milligrams per encounterd insproprlyedesiged pondssstemsnar liter for suspended solids and < 20 milligrams per 5encountered m properly designed pond systems are ltr fr biceia oxge deans or BOD >2 5 days, and this feature, in conjunction with such lIn the for 0s biochemical a o genomnd owar BO) . environmental factors as sunlight, high oxygen content enironmthen1tsand pro s, aowingd awihar s no and the presence of algal toxins, is responsible for the environmental problems, coupled with a now . ability of pond systems to reduce greatly the survival greatly increased population, led to tertiary of excreted pathogens. Indeed, protozoal cysts and treatment processes being Introduced to protect.. treatment p rocesses being introduced tolprotect helminth eggs and larvae can be completely eliminated receiving waters from further oxygen depletion, from pond effluents. Pond systems have several more toxic substances, and eutrophication. Atothe substames,and timeuitrocametclearothat advantages over other treatment methods: they are the sophisate trment technoloes w ere cheapest form of treatment, both to construct and sophistmcated treatment technologoes were not operate, with minimal requirements for foreign efficient at removing pathogenic microorganisms. ' . . effcient aountriem pahogeenvio, .exchange; their maintenance is very simple, requiring Thus, in countries where environmentalconcern only unskilled labor; they are easily designed to was acute (for example, the USA), or whlere wafluents acuerecommonlyre d (for example,t achieve any required degree of treatment; and the algae effluents were commonly reused (for example. Israel), effluent chlorination was borrowed from produced in the ponds are a potentially valuable source the water treatment industry as a way of killing of protein. - bacteria (and possibly viruses) in effluents. This technology, however, brought with it new and Literature Cited different environmental concerns.' American Public Health Association, American Water This highly simplified account illustrates the historical Works Association, and Water Pollution Control and conservative nature of the development of current Federation (1980). Standard Methods/lor the Examination waste treatment practices in industrialized countries. of Water and Wastewater. 15th ed. Washington, D.C.: These practices are not especially clever, nor logical, nor American Public Health Association. ..ltlefci-nitsntnesrlwhat Bisson. J. W. and Cabelli, V. J. (1979). Membrane filter completely doeffecti-an ifthe isam notuneessharil th enumeration method for Clost7idiuni perfringens. Applied would be done today If these same countries had the and Enuironmental Microbiology. 37, 55-66. chance to start again. (1980). Clostridiun perfijingens as a water pollution Fluid retention times in conventional sewage works, indicator. Journal of the Water Pollution Control oxidation ditches, and aerated lagoons treating Federation, 52, 241-248. domestic sewage are commonly less than 1, 3, and 6 Brodsky, M. H. and Ciebin. B. W. (1978). Improved medium days, respectively. Septic tanks typically have re- for recovery and enumeration of Pseudomnonas aeruginosa tentions of 1-3 days. These short retention times, in conjunction with temperatures that rarely exceed t 1. Waste stabilization ponds are examined in more detail in the section of that title in chapter 6. 10. See chapter 6, the section "Effluent Chlorination." 12. See the section "Reuse in Aquaculture" in chapter 7. DETECTION, SURVIVAL, AND REMOVAL OF PATHOGENS 65 from water using membrane filters. Applied and Environ- (1970). Applying bacteriological parameters to mental Microbiology. 36, 36-42. recreational water quality. Journal of the American Water Buck, A. C. and Cooke, E. M. (1969). The fate of ingested Works Association, 62, 113-120. Pseudomonas aeruginosa in normal persons. Journal of Gerba, C. P., Wallis, C. and Melnick, J. L. (1975). Fate of Medical Microbiology, 2, 521-525. wastewater bacteria and viruses in soil. Journlal of the Cabelli, V. J. (1977). Clostridiwn perjfringens as a water Irrigation and Drainage Division, American Society of Civil quality indicator. In Bacterial IndicatorsjHealth Hazards Engineers, 101, 157-174. Associated with Water, eds. Hoadley, A. W. and Dutka, B. Green, S. K., Schroth, M. N., Cho, J. J., Kominos, S. D. and J., pp. 65-79. Philadelphia: American Society for Testing Vitanza-Jack, V. B. (1975). Agricultural plants and soil as a and Materials. reservoir for Pseudomonas aeruginosa. Applied Micro- - (1978). Obligate anaerobic bacterial indicators. In biology, 28, 987-991. inadicators of Viruses in Water and Food, ed. Berg, G. pp. Hoadley, A. W. (1977). Potential health hazards associated 171-200. Ann Arbor. Mich.: Ann Arbor Science with Pseudomonas aeruginosa in water. In Bacterial Publishers. Indicators/Health Hazards Associated with Water, eds. Cabelli, V. J., Kennedy, H. and Levin, M. A. (1976). Hoadley, A. W. and Dutka, B. J. pp. 80-114. Philadelphia: Pseudomonas aeruginosa--fecal coliform relationships in American Society for Testing and Materials. estuarine and fresh recreational waters. Journal of the Jacobson, J. A., Hoadley, A. W. and Farmer, J. J. (1976). Water Pollution Conztrol Federation, 48, 367-376. Pseudomonas aeruginosa serogroup 11 and pool- Chakrabarty, A. K., Narayan, K. G. and Chandiramani, N. associated skin-rash. American Journal of Public Health, K. (1977). Association of Clostridium pezfringens type A 66, 1092-1093. with human diarrhoeal cases. Indian Journzal of Medical Levin, M. A. (1977). Bifidobacteria as water quality Research, 65, 495-499. indicators. In Bacterial Indicators/Health Hazards Cross, A. S. (1979). Pseudomonas aeruginosa. In Principles Associated with Water, eds. Hoadley, A. W. and Dutka, B. and Practice of Infectious Diseases, eds. Mandell, G. L., J. pp. 131-138. Philadelphia: American Society for Testing Douglas, R. G. and Bennett, J. E. pp. 1705-1720. New and Materials. York: John Wiley. Levin, M. A. and Cabelli, V. J. (1972). Membrane filter Department of Health and Social Security (1969). The technique for enumeration of Pseudomonas aeruginosa. Bacteriological Examination of Water Supplies. Reports on Applied Microbiology, 24, 864-870. Public Health and Medical Subjects, no. 71. 4th ed. McCausland, W. J. and Cox, P. J. (1975). Pseudomonus London: Her Majesty's Stationery Office. infection traced to motel whirlpool. JournEal of Drasar, B. S. and Hill, M. J. (1974). Human Intestinal Flora. Enviironmental Health, 37, 455-459. London: Academic Press. McFeters, G. A., Bissonnette, G. K., Jezeski. J. J.. Thomson, Dufour, A. P. (1977). Escherichia coli: the fecal coliform. In C. A. and Stuart, D. G. (1974). Comparative survival of Bacterial Indicators/Health Hazards Associated witli indicator bacteria and enteric pathogens in well water. Water. eds. Hoadley, A. W. and Dutka, B. J. pp. 48-58. Applied Microbiology, 27, 823-829. Philadelphia: American Society for Testing and Materials. McGarry, M. G. and Stainforth, J. (1978). Compost, Fertilizer Dutka, B. J. and Kwan, K. K. (1977). Confirmation of the and Biogas ProductionJifomHutnat and Farm Wastes in the single-step membrane filtration procedure for estimating People's Republic of China. Ottawa: International Pseudomonas aeruginosa densities in water. Applied and Development Research Centre. Environmental Microbiology, 33, 240-245. Mara, D. D. (1974). Bacteriology for Sanitary Engineers. Evison, L. M. and Morgan, S. (1978). Further studies on Edinburgh: Churchill Livingstone. bifidobacteria as indicators of faecal pollution in water. Parker, M. T. (1971). Causes and prevention of sepsis due to Progress in Water Technology, 10, 341-350. Gram-negative bacteria: ecology of the infecting or- Feachem, R. G. A. (1975). An improved role for faecal ganisms. Proceedings of'the Royal Society ofMedicine, 64, coliform to faecal streptococci ratios in the differentiation 979-980. between human and non-human pollution sources. Water Qureshi, A. A. and Dutka, B. J. (1979). Microbiological Researchi, 9, 689-690. studies on the quality of urban stormwater runoff in Feachem, R. G. A., Bradley, D. J., Garelick, H. and Mara, D. Southern Ontario, Canada. Water Research, 13, 977-985. D. (1980). Health Aspects of Exereta and Sullage Raghavachari, T. N. S. and lyer, P. V. S. (1939). The coli- Management: A State-of-the-Art Review. Appropriate aerogenes index of pollution used in the bacteriological Technology for Water Supply and Sanitation, vol. 3. analysis of water. Indian Journal of Medical Research, 26, Washington, D.C.: The World Bank, Transportation, 867 875. Water and Telecommunications Department. Seyfried, P. L. and Fraser, D. J. (1978). Pseudomonas Geldreich, E. E. (1966). Sanitary , , K of Fecal aeruginosa in swimming pools related to the incidence of Coliforms in the Environment. Water Pollution Control otitis externa infection. Journal of Health Laboratory Research Series no. WP-20-3, US Department of the Science, 15, 50-57. Interior. Washington, D.C.: Government Printing Office. Washburn, J., Jacobson, J. A., Marston, E. and Thorsen, B. 66 HEALTH HAZARDS OF EXCRETA (1976). Pseudomonas aeruginosa rash associated with a Wheater, D. W. F., Mara, D. D. and Oragui, J. (1979). whirlpool. Journal of the A4merican Medical Associa ion, Indicator systems to distinguish sewage from stormwater 235, 2205-2207. run-off and human from animal faecal material. In Wheater, D. W. F., Mara, D. D., Jawad, L. and Oragui. J. Biological Indicators of Water Quality, eds. James, A. and (1980). Pseudomonias aeruginosa and Escherichia coli in Evison, L. pp. 21/1-21//27. Chichester: John Wiley. sewage and fresh water. Water Research. 14, 713-721. Note added in proof Recent work in Yorkshire, England (Oragui 1982) has led to the development of bacteriological methods for distinguishing between human and animal fecal pollution of waters. Streptococcu.s bouis, which can be enumerated in water samples by the method of Oragui and Mara (1981), appears to be excreted exclusively by animals, whereas sorbitol-fermenting strains of Bifidobacteritmn adolesce72tis and B. breve are only excreted by man. Enumeration media for both sorbitol-fermenting and total bifidobacteria are described by Oragui (1982). These methods for distinguishing between human and animal pollution are currently being evaluated in Mexico, Nigeria and Zimbabwe. References Oragui, J. I. (1982). Bacteriological Methods Jbr tlze Distinction between Hunian and Animal Faecal P(dla,noa. Ph.D. Thesis. Leeds: University of Leeds. Oragui, J. 1. and Mara, D. D. (1981). A selective medium for the enumeration of Streptococcus bouis by membrane filtration. Journal of Applied Bacteriology, 51, 85-93. 5 Health Aspects of Excreta and Night Soil Systems IN THIS AND THE NEXT CHAPTER, the health impli- bowls may block up. Fouled and unhygienic pit cations of the principal varieties of excreta collection latrines are found all over the wbrld, often because they and treatment systems are discussed. These are have been constructed in communities previously separated into night soil (or "dry") and sewage (or accustomed to defecation on the open ground who "wet") systems. (The health implications of reuse and have also had inadequate community involvement or effluent-discharge practices are considered in chapter health education. Fouled pit latrines become a focus of 7.) Little attention is paid here to the technical details disease transmission and may make health matters of the systems examined, except to those bearing on worse than before the sanitation intervention. specific health problems. The reader wishing more information on technical aspects should consult the Odor second volume of this series (Kalbermatten and others 1982), the related document published by the Pit latrines with squatting slabs often are malo- International Development Research Centre dorous. If they are, they may not be used and thus (Rybczynski, Polprasert, and McGarry 1978), and cannot yield any potential benefits in improved standard sanitary engineering texts. In this chapter, health. Odors can virtually be eliminated by fitting a three excreta collection systems-the pit latrine and its vent pipe to the pit. This pipe should be at least 100 various modifications, the composting latrine, and millimeters in diameter, painted black, and fitted on the cartage systems-are described, and the discussion sunny side of the latrine so that it can heat up, the heat concludes with an examination of the health creating an updraught. [See note on page 82.] implications of dry treatment of night soil by trenching and composting. Excreta collection and treatment by Insect breeding wet systems are examined in chapter 6. Pit latrines with squatting slabs will usually become breeding sites for flies. Flies that visit a pit latrine to Pit Latrines breed or feed may carry pathogens when they leave and thus promote disease transmission. If the pits are wet, Pit latrines are the simplest of all on-site disposal they may also become Culex pipiens breeding sites. Well systems. Excreta fall into a hole in the ground, and a constructed pits with pour-flush bowls will not allow new pit is dug when the hole is about two-thirds full such insect breeding. If squatting slabs are used, a (see figure 5-1). A ventilated improved pit (vip) latrine, vertical vent pipe 100-200 millimeters in diameter, and a modified pit latrine called a ROEC (Reed covered by a fly screen, and combined with a dark Odorless Earth Closet), are shown in figures 5-2 and 5 interior to the superstructure-will greatly reduce 3, respectively. Pits are covered by sqatting slabs, seats, both the amount of fly breeding and the escape of any or pour-flush bowls. flies that do breed. Flies breeding in the pit will be attracted by the light coming down the vent pipe and Cleanliness will attempt to escape by this route, only to be prevented by the fly screen. The effect of vent pipes on In all latrines cleanliness is of the utmost importance. mosquito breeding in wet pits remains uncertain and Squatting slabs easily become fouled and pour-flush the latest findings are reviewed in chapter 36. 67 68 HEALTH HAZARDS OF EXCRETA survival is of no concern because all pathogenic organisms will be dead. In some areas, however, two Open for alternating pit sites are used, a pit is dug out a year or ventilation two after closing, and the contents are used as fertilizer. This system resembles the double-vault composting toilet (see below) except that it operates on a longer cycle. If the pit has been left for a minimum of one year. there will be no viable pathogens (except, possibly, a few Ascaris eggs). The chances of viable Ascaris eggs being present are greater if the pit is wet and partly below the water table. The risk involved in reusing material that has been buried for at least 12 months is -Removable small, however, and the pit contents may immediately be used on the fields with confidence. [See note on page Vent hole W Base 82.7 Ground level _ Ground lee .,. ., , ................ ... _ ,,Groiunddwater pollution /W/ t+-B. wConcreiu (Jr \;u tilc. sheet metal, (noncorrosie) or corrugated metal roof 100- t 2 diame vent pipe Joint detail i Removablc cover 11)11_ _ /'-mm,4. concrete. I sections JOG-mm bl< ock. .^ or-, i 0 n Sover sectons a-a St _-_ subStit d fr stor manhole C ston , a a locascaled with F a _ E v m~~rlortar or tar.,_ ___L ;[ < _ 2.000to _ F '~~~~~~~~~~~~~~~~~.00) \mm 31100 mm a I q F I()()~~~~~~~10-mm concrete.,l -111" ~~~~~lvq 7, s 2(00-mm block, or ax t!6 200-mm brick liner Section a-a Section b-b (vent pipe not shown) Figure 5-3. Reed0Odorltess Earth Closet (ROEC) (dimensions in millimeters). Pedestal seat with curved chute may be substituted forsquattingplate. Constructionmaterials and dimensions forthesuperstructuremayvary according to local practice. From Kalbermatten and others (1982) HEALTH ASPECTS OF EXCRETA AND NIGHT SOIL SYSTEMS 71 Fly-proof mesh 150-mm-diameter vent pip Long-handled cover to _ _Ii squatting plate Squattingl Removable < L t t I E ~~~~~cover r= _.* .......-- ..._ n- or A-shaped channels- A i r; M. Air Ground level Air _ z^^> i ~~~~~~~~~Air_ o L L H~~~~~~~~~vuaulitS Decomposing ) ) ( * .C c<.) Gravel soakaway waste 's Figure 5-4. 'tlulo ii" continuous-composting toilet. From Kalbermatten and others (1982); adapted from a drawing by U. Winblad Only limited and inadequate microbiological data main factors affecting the survival of excreted exist on continuous composters (Gurak 1978; re- pathogens are time and temperature. Temperature in viewed by Feachem, Mara and Iwugo 1980). The batch the composting pit or vault depends on the air supply, composter is common in China and Vietnam, and the the C:N ratio, and the moisture content. If the most usual design is the double vault (see figure 5-5). digestion is anaerobic, the temperature may remain Again, no appreciable microbiological data on these ambient or it may rise at most to around 35°C. If it is toilets have been located, although such data may exist aerobic, the temperature will rise to the 50-70°C range in China and Vietnam. if the C:N ratio and moisture content are correctly regulated. These conditions may be difficult to achieve, especially in arid developing countries where little Pathogen survival in product organic material (needed as a source of carbon) is In both kinds of composting toilet, the composted available for adding to the wastes. product is used as an agricultural fertilizer and soil It is certain that double-vault composters will be conditioner. It is important, therefore, that pathogen anaerobic, and it is probable that multrums will be destruction should be as complete as possible. The two also. Anaerobicity and ambient temperature certainly 72 HEALTH HAZARDS OF EXCRETA ,_ 75-mm r. unplasticized vent pipe Air space Removable 690 1,000 640 superstructure formed from timber frame .__. _ ., and galvanized …jr- - - - -1- - -- milled steel Icr r---1 r--~~ ---1 1 ~ Concrete Concrete -1 = -Fiberglass I ,,,,~~~ Concreteet t | l l 1l ~~~~~closure cover acs oe I oe ~~"'~~'~~' access cover n S ntosecond 50, .i lvault F.- L- - ON I__jfiio ___ ~ ~~~~~~Concret L °S° 450 | Plan Section Model used in Botswana 50 _ _ _ _ _ 25 3 3-mm ferrocement 50 1,050 450 Plan Section Model used in Tanzania Figure 5-5. Double-ivault comlposting (DVC) toilet (dimensions in millimeters). From Kalbermatten and others (1982); top, adapted from a drawing by R. A. Boydell 1,420 73 Ash 340 100 ~540 10034 storage Urn area 0; outlet Superstructure corner posts Plain Bamboo wall cladding 130 ~ ~ ~ Urine removal port b , 1,,xv,, ... . 4 . ,,,^sv,+ ] , ................. b 250 150 1140 720 1401 100 100 1.200 Section a-a 1,620 100 500 500 100 - I141 < 11401- -1 500 O Section b-b Figure 5-5 (continiued) Model used in Vietnam 74 HEALTH HAZARDS OF EXCRETA EXCRETA Viruses --- -- Bacteria - - Composting toilet wifh 3-month minimum retention time. Protozoa - COMPOST Helminths 0 Helminths Figure 5-6. Pathogen flow through a batch composting toilet (double-vault) are the correct, conservative assumptions to make above a bucket which is filled within a few days by the where pathogen removal is the concern. Pathogen excreta of an average family (see figure 5-7). The bucket removal then depends on the retention time in the unit. is positioned adjacent to an outside wall and is There appears to be a wide variation in retention time accessible from the street or back lane. A night soil used in both the multrum (continuous) and double- collector ("scavenger" or "sweeper") will call vault (batch) systems, and the pathogen removal regularly-preferably every day, but more typically efficiency of any given design can be estimated by once or twice a week-to empty the bucket. consulting table 5-1. It is clear from the table that a minimum retention time of 3 months will yield a product free of all pathogens except the more persistent Table 5-1. Probable pathogen content in final helminth eggs, as visualized in figure 5-6. Three product of anaerobic composting toilets operating at possible pathogen control strategies can be adopted for ambient temperatures in warm climates compost: Retention time Pathogen (months) * To use the compost as produced and accept the level of risk involved. This risk could be reduced to 1 2 3 4 6 8 10 sufficiently low levels by using the compost only to prepare ground prior to planting or by not Viruses applying compost within 2 months of harvesting. Enterovirusesa + + 0 0 00 0 * To apply the compost only to industrial or fodder Bacteria crops. Fecal coliforms + + 0 0 0 0 0 * To provide further treatment for the compost Leptospira spp. 0 - 0 0 0 0 0 through heating it (probably impracticable) or Shigella spp. + 0 0 0 0 0 through mixing it with an ovicide (also often Vibrio cholerae + 0 0 0 0 0 0 impracticable). Protozoa Balantidium coli + 0 0 0 00 0 The first of these strategies is probably the most Entamoeta realistic, and the quality of the product will become Giardia lamblia - 0 0 0 0 0 0 better as the retention time is increased beyond 3 months. ~~~~~~~~~~~~~Helminth eggs months. Ascaris lumbricoides + + + + + + + + + + + Hookwormsb + + 0 0 0 0 0 Cartage Systems Schistosoma spp. 0 0 0 0 0 0 0 Taenia spp. + + + + + + + + + + + Cartage systems include a variety of technologies by Trichuris trichiura ++ ++ + + + - 0 which night soil is periodically removed from containers in or near the house. One of the oldest- concontration, and, generally, least hygienic-systems is the bucket a. Includes polio-, echo-, and coxsackieviruses. latrine. A squatting slab or seat is placed immediately b. Ancylostoma duodenale and Necator americanus. HEALTH ASPECTS OF EXCRETA AND NIGHT SOIL SYSTEMS 75 Squatting plate Fly-proof door Paved surface and drain / Ground surface _ . ~~25 mm, _ -vzt '.v: :.00 maximuma.- _ f-,,- ;eM Soakage pit for bucket washwater L - Bucket latrine Night-soil collection by dipper and bucket (here a vault rather than a bucket is located in house) Night-soil bucket and scraper Cartage wheelbarrow for three or six buckets Figure 5-7. Bucket latrine and cartage. Fly-proof doors and paved surfaces and drains are commonly missing in most existing bucket latrines. From Kalbermatten and others (1982); top left, adapted from Wagner and Lanoix (1958); top right, from a photograph courtesy of Michael G. McGarry; bottom, Department of Social Welfare, Ahmedabad, India Many households in East Asia, and elsewhere, store in which the night soil is deposited, collected, their excreta (plus the small amounts of water used for transported, treated, and reused. Each of these will be pour flushing and anal cleansing) in sealed vaults considered in turn. under or beside the house (see figure 5-8) that are emptied by a vacuum truck about once every 2 weeks. Night soil deposition This system has relatively high operating costs but may have relatively low initial costs. It is suitable for high- The two normal methods of deposit are into the density urban areas where access by truck is possible bucket or vault. Both these depositories can be and truck maintenance facilities exist. The health satisfactory if they are hygienically maintained. The dimensions of a cartage system depend on the manner bucket, a smaller vessel than the vault, is more likely to 76 HEALTH HAZARDS OF EXCRETA Val5-mm vent pipe s to tVacuum tanker Toilet-_ ~Manhole t a House / OffseVault v Vault below squatting plate Vent Hose to tanker House 1 Offset vault Figure 5-8. Alternative designsjor rault toilets. From Kalbermatten and others (1982) overflow and to contaminate its surroundings. The to develop from egg to adult, and so a bucket emptied bucket latrine is also almost certain to be malodorous, every 5 days will not permit fly breeding, provided it is and this will discourage use. In contrast, the vault can well cleaned each time it is emptied. Vaults, however, be ventilated, making a hygienic and pleasant latrine. are emptied less frequently, and fly breeding is a The possibility of fly breeding depends on the danger. Breeding can be reduced by installing a pour- frequency with which the depositories are emptied. flush water seal to prevent access of adult flies or by Houseflies and blowflies require a minimum of 1 week installing a vent pipe with a fly screen similar to the one HEALTH ASPECTS OF EXCRETA AND NIGHT SOIL SYSTEMS 77 recommended above for pit latrines. A pour-flush table 2-2). This risk is not simply to the sweepers water seal is probably the only reliable method of themselves, but also to anyone who lives on or walks, preventing fly breeding in vault latrines. plays, or works in the streets or back lanes where the night soil has been spilled. The risk to children is Night soil collection obviously great because they commonly play in back lanes and alleys. The latent pathogens that develop on Collection of night soil from vaults by vacuum soil (category ti-hookworms, Ascaris, and Trichuris) trucks can be hygienic and risk free-provided that the may well develop into their infective stages where they outlet pipe from the vault is in good repair and that all have been spilled in fresh night soil, and there is fittings on the truck and suction hose are well evidence that the cartage of night soil is partly maintained. A little spillage is probably inevitable, but responsible for the high levels of Ascaris egg it can be reduced to an acceptable minimum by good contamination found in the soil of some cities. Vacuum equipment and well-trained operating personnel. trucks, by contrast, can transport night soil through the By contrast, collection from bucket latrines is always streets with minimal risk of spillage. messy. The worst method is to empty the buckets and immediately return them, which causes the latrine area to become progressively more fouled (with consequent risk of infection to the household, the sweeper, and Night soil treatment is also discussed in conjunction passersby). Emptying the bucket, rinsing it out, and with wet systems in the next chapter. Night soil can be returning it is also undesirable and will probably result digested and dewatered (as is sludge), it can be mixed in the washwaters being deposited in the street. The with sewage and treated in conventional plants, or it best arrangement is to replace the bucket by another can be sluiced into waste stabilization ponds (see cleaned and disinfected one, with dirty buckets being chapter 6 for descriptions of these treatments). Night returned to a central depot for cleaning and soil can also be treated by dry systems, such as disinfection. Operation of this system is facilitated by trenching or, preferably, composting. Following use of a color code in which all buckets collected on adequate treatment, night soil can be used in Monday, for example, are red and the replacement agriculture, aquaculture or gas production (see chapter buckets green. Such a bucket-replacement system is 7). often not feasible on a large scale because of the Where trenching is used, the health implications can difficulty of transporting large numbers of buckets. It be serious. A badly managed and inadequately can, however, work well in army camps, prisons, controlled trenching ground will be a major health disaster relief camps, and other institutions of limited hazard to all who work on it or to those-children, for size. example-who may gain access. The families and It is clear that the risks from a cartage system depend close contacts of these people are also at risk. The greatly on the quality and regularity of the service proper management of a trenching ground is largely provided. The system is sensitive to a few days' common sense: trenches should be at least 0.6 meters interruption in collections, whether from mechanical deep and should be filled with night soil to a depth of breakdown or absence of the sweeper.4 not more than 0.3 meters; they should then be rapidly covered with tamped earth, to make a small mound of earth over the trench, after which they are left for at least 2 years. Yet, however well managed the surface of The differences in health risks between the a trenching ground is, the risk of groundwater alternative bucket and vault-and-truck systems be- pollution may always be present. This risk is minimized come obvious at the transport stage. The worst system by careful location of the trenching ground following a is the one in which buckets are emptied by hand into hydrogeological survey. Given these limitations, in open carts or into larger buckets, which are then many situations the most appropriate and attractive carried by hand or on yokes. Under these arrange- method of night soil treatment is by mixing it with ments there will always be spillage. People who come refuse and composting (see below). into contact with this fresh night soil risk infection from any of the nonlatent pathogens (categories I and it in Night soil reuse 4. See chapter 8. the sections "Influence of Social Structure and Organization" and "Social and Organizational Aspects of Excreta Reuse is described in detail in chapter 7. The reuse of Cartage Systems." untreated night soil in agriculture is a widespread 78 HEALTH HAZARDS OF EXCRETA practice, but one that is to be strongly condemned for thermophilic microorganisms, and degradation is its health hazards. There is much evidence that the use more rapid and usually free of odor. of untreated night soil on crops contributes to the A newly erected compost pile will contain entrapped transmission of infection to those working in the fields oxygen and, if the other factors mentioned above are and. to a lesser (but still significant) degree, to those correctly regulated, thermophilic aerobic processes handling or consuming the crops. Treatment or will be established and the temperature at the center of storage of night soil should therefore always be the pile will rapidly rise to 55°C or above. As the provided prior to its reuse. available oxygen is used up, however, the process will become progressively more anaerobic and tempera- tures will fall. There are three methods commonly used Composting to sustain the supply of oxygen and therefore maintain thermophilic temperatures: the pile is regularly turned, Again it must be stressed that temperature and time or ventilation tubes are arranged in the pile, or forced are the two most important factors in the achievement aeration is provided by blowers or suckers. In the last of low pathogen survival in waste treatment processes. two cases, the pile is usually lagged to prevent heat loss. In the treatment of night soil or sludge for reuse, an Temperatures can rise to 80°C in these well-managed, almost pathogen-free product is required. This is only thermophilic, aerated composting systems, and it is achieved by processcs incorporating long retention possible to ensure that all parts of the pile spend several times (such as ponds or protracted digestion and hours at temperatures above 60°C-of the utmost drying; see the next chapter), heat (such as thermo- importance in curtailing pathogen survival. philic digestion; see the next chapter), or thermophilic composting (discussed here). The attraction of thermophilic composting is that it can yield a safe Pathogen survival product for reuse in a relatively short time (<2 Pathogen survival in compost systems depends months) and that it does not require an external source upon the time-temperature characteristics of various of energy for heat. In addition, composting tech- parts of the pile. The death curves derived for some nologies are available that are relatively low cost and pathogens, discussed further in Part Two, are plotted labor intensive. The compost produced is a useful soil in figure 5-9. Time-temperature points above the curve conditioner and source of plant nutrients that may for each pathogen represent certain, total destruction. increasingly be in demand among poor farmers as the It is clear that enteroviruses and Ascaris eggs are the cost of industrially produced fertilizers rises (Food and most hardy, but the time-temperature combinations Agriculture Organization 1975). given in the note to figure 5-9 will ensure their Composting has been thoroughly reviewed by destruction. If all parts of a compost pile can be Gotaas (1956), and more recent accounts are provided brought to a time-temperature state within the "safety by Haug (1979); Polprasert, Wangsuphachart, and zone" in figure 5-9, complete pathogen destruction Muttamara (1980); and Shuval, Gunnerson, and Julius should be guaranteed (see figure 5-10). There are two (1981). A wide range of fecal composting technologies possible exceptions. First, spore-forming bacteria- are available. They all incorporate the mixing of night such as Clostridium perfringens, discussed in chapter soil or sludge with a carbon source (such as refuse or 4-are more resistant but present little risk. Second, sawdust) to achieve a C:N ratio of approximately hepatitis A virus appears to resist rapid heating, and its 20-30. Moisture content (20-60 percent) must also be ability to survive temperatures around 60'C for several regulated for optimal performance, with wetting or hours is unknown. turning (for drying) at appropriate intervals. Much of the literature on pathogen survival in The most important feature of composting, from the compost, which has previously been reviewed by others health viewpoint, is the temperature achieved-and (for intance, Kawata, Cramer, and Burge 1977; Krige this depends on the oxygen content of the pile, C:N 1964; Nell and Wiechers 1978; Reeves 1959; Shuval, ratio, moisture content, particle size, and pH. If the Gunnerson and Julius 1981; Wiley 1962; Wiley and process is anaerobic, temperatures will remain at (or Westerberg 1969; WHO Intemational Reference only a little above) ambient temperature, and Centre for Wastes Disposal 1978) is reported in Part mesophilic microorganisms will predominate. Foul- Two. This literature indicates that a well-designed smelling gases are usually produced, and the process of system under good management produces a pathogen- degradation proceeds slowly. If the process is aerobic, free, or almost pathogen-free, compost if all sections of substantial heat is generated by the proliferation of the pile reach the required temperature for the required HEALTH ASPECTS OF EXCRETA AND NIGHT SOIL SYSTEMS 79 70 70 Enteric viruses 65 65 Shigella \/ 60 - SAFETY ZONE 60 so- 'N 50 Vibrio cholerae \ , , G. 45 45 45' N. 40 -N - Ascaris -40 'N N\> & Salmonella 35 _ X - _ 35 30 _ ;_30 25 _ ,Emn-aoba \ 25 ',histolytica 20 I 1 20 0.1 1 1 0 I 100 1, 00 1 '°° I'°°° I day I week I month I year Time (hours) Figure 5-9. Influence of time and temperature on selected pathogens in night soil and sludge. The lines represent conservative upper boundaries for pathogen death-that is, estimates of the time-temperature combinations required for pathogen inactivation. A treatment process with time-temperature effects falling within the "safety zone" should be lethal to all excreted pathogens (with the possible exception of hepatitis A virus at short retention times). Indicated time temperature requirements are at least: I hour at > 62°C, I day at > 50'C, and I week at >, 46°C. For more detail on the time-temperature combinations lethal to these and other pathogens, see the graphs in chapters 9, 15-17, 20, 22, 23, 32, and 34 of Part Two (from which this composite was made) 80 HEALTH HAZARDS OF EXCRETA EXCRETA Viruses --- - Bacteria -- 3m Wel/-managed (olparts of the pilet required time-temperature) thermophiiic compostinIg. Protozwoa COMPOST Helminths > Figure 5-10. Pathogen flow throuigh a well-managed thermophilic compostinlg process time. The organism most likely to survive this useful to the staffin charge. Fly breeding will, of course, treatment is Ascaris, and Ascaris eggs may therefore be fluctuate markedly with the seasons, irrespective of the used as the indicator of successful composting. condition of the compost pile. Fly breeding Literature Cited One of the major problems in managing composting operations is fly control. All raw materials used for Feachem, R. G. A., Mara, D. D. and Iwugo, K. 0. (1980). composttflies and are good media for fly Alternative Sanitation Technologies for Urban Areas in brmpee ting. Flies cattract eggs in the material attheplace Africa. Appropriate Technology for Water Supply and breeding. Flies can lay eggs in the material at the place Sanitation, vol. 7. Washington, D.C.: The World Bank, of collection or during the handling of the material at Transportation, Water and Telecommunications the compost site. Different species predominate under Department. different conditions, but good control measures should Food and Agriculture Organization (1975). Organic affect them all. Fly larvae cannot survive temperatures materials as fertilizers. Soils Bulletin, 27. above 50'C, and so, as for other pathogens, the Gotaas H. B. (1956). Composting. Sanitary disposal and achievement of high temperatures in all parts of the pile reclaniation of organic wastes. Monograph Series no. 31. is the essential requirement for control. Fly larvae may Geneva: World Health Organization. however, migrate along temperature gradients to seek Gurak, R. S. (1978). Final Report on the Alternative Waste the cooler parts of the pile (such as the edges or the Disposal Methods Project in Tanzania, East Africa: Chemical, Microbiological and Parasitological Results. areas near ventilation shalts). These larvae may be Ottawa: International Development Research Centre. destroyed by effective and well-controlled turning orby Haug, R. T. (1979). Engineering principles of sludge lagging unturned piles. The use of insecticides in composting. Journal of the Water Pollution Conjtrol compost piles is not desirable unless it has been Federation, 51, 2189-2206. demonstrated that these chemicals will not affect the Kalbermatten, J. M., Julius, D. S., Gunnerson, C. G. and composting process or the acceptability of the product Mara. D. D. (1982). Appropriate Sanitation Alternatives: to farmers. Plannling and Design Manual. World Bank Studies in Fly breeding may pose a general problem in all Water Supply and Sanitation 2. Baltimore. Md.: Johns composting systems. The level of fly breeding provides Hopkins University Press. some gauge ofhow successfully the pile is managed and Kawata, K.. Cramer, W. N. and Burge. W. D. (1977). whether it is being thoroughly heated, with minimum Composting destroys pathogens in sewage solids. Water fly breeding an explicit goal for the management of all and Sewage Works, 124, 76-79. compstig plnts It s pssibe t montorthe eve of Krige. P. R. (1964). A survey of the pathogenic organisms and composthng plants. It IS possible to monitor the level of helminthic ova in composts and sewage sludge. Jour nal fly breeding by positioning flytraps at appropriate sites and Proceedings of the Institute of Sewage Purification, part around the plant and recording the daily gatch. This 3, 215-220. provides a continuous and immediate check of Nell, J. H. and Wiechers, S. G. (1978). High temperature management and temperature control that is most composting. Water South Africa, 4, 203-212. HEALTH ASPECTS OF EXCRETA AND NIGHT SOIL SYSTEMS 81 Polprasert, C., Wangsuphachart, S. and Muttamara, S. Wagner, E. G. and Lanoix, J. N. (1958). Exereta Disposalfor (1980). Composting night soil and water hyacinth in the Rural Areas and Small Communities. Geneva: World tropics. Compost Science/Land Utilization, 21, 25-27. Health Organization. Reeves, J. B. (1959). Sanitary aspects of composted sewage, Wiley, B. B. and Westerberg, S. C. (1969). Survival of human sludge and sawdust. Sewage and Industrial Wastes, 31, pathogens in composted sewage. Applied Microbiology, 18, 557-564. 994-1001. Rybczynski, W., Polprasert, C. and McGarry, M. G. (1978). Wiley, J. S. (1962). Pathogen survival in composting Lowv-Cost Technology Options fbr Sanitation: A State-of- municipal wastes. Journal of the Water Pollution Control the-Art Review and Annotated Bibliography. IDRC-102e. Federation, 34, 80-90. Ottawa: International Development Research Centre. WHO, International Reference Centre for Wastes Disposal Shuval, H. I., Gunnerson, C. G. and Julius, D. S. (1981). (1978). Compost: An Annotated Bibliography on Compost, Night-soil Composting. Appropriate Technology for Water Compost Quality and Composting, 1971-1977. Dubendorf, Supply and Sanitation, vol. 10. Washington, D.C.: World Switzerland: wHo International Reference Centre for Bank, Transportation, Water and Telecommunications Wastes Disposal. Department. Note added in proof Since this chapter was written, there have been a number of developments in the design of ventilated improved pit latrines, especially with regard to ventilation mechanisms (wind shear across the top of the vent pipe is now known to be more important than absorption of solar radiation) and the use oftwin pit V IP latrines (which are permanentstructures requiringeach pit to be emptied in alternate years). There have also been significant developments in superstructure design, notably the spiral shape used in Zimbabwe which obviates the need for a door, while still ensuring privacy and good fly control. In rural Zimbabwe spiral latrines have been built almost entirely out of local materials and at a financial cost to the householder of only US$tO. These and other developments are described in a series of working papers and technical notes prepared by the Technology Advisory Group established by the World Bank as executing agency for the United Nations Development Programme Interregional Project INT181,/047 "Development and Implementation of Low-cost Sanitation Investment Projects", they may be obtained by writing to The Project Manager, UNDP INT/81/047, Transportation and Water Department, World Bank. 1818 H St NW, Washington DC 20433. USA. 6 Health Aspects of Sewage Systems IN THIS CHAPTER the "wet" systems, which collect and Pathogen survival treat excreta diluted by water, are considered. Not only Two fundamental processes affecting pathogen conventional sewerage and sewage treatment systems removal in waste treatment operate in septic tanks and are included, but also on-site sewage .disposal methods aquaprivies. First, solids settle to the sludge layer at the such as septic tanks and aquaprivies. The reader bottom of the chamber; with them settle any bacteria wishing more technical information should refer to o Kalberatten and ohers 1982) Rybcynski or viruses adsorbed onto the solids and any helminth Polprasert and McGarry (1978); Mara (1976); Metcalf eggs or protozoal cysts sufficiently dense to settle. The and Eddy, Inc (1979) Okun and Ponghis (1975); and settling action of the tanks is their chief function and Tebbutt (1983).' their efficiency depends on retention time and design (particularly with regard to baffles or compartments designed to prevent hydraulic short-circuiting and to create quiescent conditions). Those pathogens which Aquaprivies and Septic Tanks do not settle will remain in the liquid layers and eventually pass out of the tanks in the effluent. The Aquaprivies and septic tanks are similar systems and degree to which their concentration decreases depends are thus examined together. They both incorporate a on retention time and on their reaction to the rich, sealed settling chamber in which solids accumulate and anaerobic liquor in which they are held. out of which an effluent flows. Generalizations about pathogen removal in aqua- privies and septic tanks are difficult to make because Technical description designs and retention times vary enormously. Moreover, as the sludge layer of a septic tank builds up, Septic tanks typically are located in the gardens of retention times decrease and the pathogen content of individual houses having water connections and full the effluent increases. It is common to find operating plumbing; they receive all wastewater from a house aquaprivies and septic tanks that are long overdue for and have liquid retention times in the order of 1-3 days, desludging; in these cases any good design features and after which the effluent normally goes to a soakaway. pathogen removal abilities initially present will largely Aquaprivies are located directly under the toilet; they have been negated by the failure to desludge at the usually receive only excreta and small volumes of correct, regular intervals. flushing water and have liquid retention times as high Because the quality of aquaprivy effluent depends as 60 days, after which effluents flow to soakaways or greatly on retention time, the system is sensitive to into small-bore sewerage systems. In some designs variations in hydraulic loading. If the loading rate is aquaprivies also receive sullage, in which case retention too low and the water level is allowed to fall below the times may decrease to a few days (depending on the drop pipe, the result will be the release of offensive odor volume of sullage produced). Designs for septic tanks and, probably, large-scale mosquito breeding. and aquaprivies are shown in figures 6-1 and 6-2. Attempts to guarantee an adequate water level by running sullage into the tanks, however, will shorten retention times and raise the pathogen content of the effluent. 1. See also Part Two for a detailed review of the pathogen removal There are few available data on the quality of effluent capabilities of the treatment systems examined in this chapter. from aquaprivy installations. The literature on septic 83 84 HEALTH HAZARDS OF EXCRETA Inlet Compartment Outlet baffle Outlet 'FT !r'' ; ''' ' Outlet Inlet - - @ E . _ = _ 9 i t _ t40 percent Scum I _ of liquid depth . Clear space _ L .-Sclear space _ Scum ____________Scum 3 length V 1 length Conventional two-compartment Conventional two-compartment septic tank septic tank with inlet with baffle walls connector and outlet "T" Effluent weir Sludge . - - * cha~~~~~~ ~ ~~~~nnel -. . 1 / / ra tffl 1 ~~~~~~~~~To L ... . * : . Fit ; . te TXdrainfield 7 ~ ~ ~ ~ /' Toilet wastes Sullage and settled wastes Two-compartment septic tank with upflow filter Three-compartment septic tank Animal excreta Sullage inlet Slurry 600-mmn diameter and animal exreta removal access manhole 1 [ X 1. a | g 42 : a Human Human - - exereta h excreta - h b __ Equal Equal Equal Section a-a Section b-b Three-compartment septic tank for resource recovery Figure 6-1. Septic tanik designs. From Kalbermatten and others (1982) HEALTH ASPECTS OF SEWAGE SYSTEMS 85 a r ra L 900 _ ~~~~~~~~~~~~~~~~~Outlet -- ___ a 0 t ) 1-- S ~to soakaway 25-mm I I I vent pipe I Removable slab I I I I for desludging access L--L - - - ___J Plan 25-mm vent pipe Removable slab for desludging access Outlet to soakawav 1,370 Section a-a Figure 6-2. Cont entionzul oqoopriryi (dimensions in millimeters). From Kalbermatten and others (1982): adapted from Wagner and Lanoix (1958) 86 HEALTH HAZARDS OF EXCRETA tanks, reviewed in detail in Part Two, will therefore be is probable that an aquaprivy incorporating baffles summarized here. In a septic tank having a normal and with a retention time this long will produce an retention time (1-3 days), the effluent produced will be effluent of substantially better quality than a normal rich in all pathogens contained in the influent. This septic tank (or, indeed, than a conventional sewage flow is illustrated in figure 6-3. Removal of various works). It must be assumed at present, however, that types of pathogens from the effluent is as follows: aquaprivy and septic tank effluents are highly patho- genic (figure 6-3). If they flow to sewers, they require Viruses Re0t,cion2 (log10 tout) treatment (probably in ponds) prior to any reuse. If Bacteria 0-2 they flow to soakaways, a groundwater pollution Protozoa 0-2 hazard may exist.2 Helminths 0-2 Badly maintained and inadequately desludged tanks Conventional Sewage Treatment will have especially poor pathogen removal character- istics. A proportion of all pathogens will settle, and fresh A variety of unit processes combine to form sludge will therefore contain significant numbers of conventional sewage treatment; commonly used pathogenic bacteria, viruses, protozoal cysts, and combinations are shown in figure 6-4. These com- peamithogeni eggs eri (i reu6- Wenero oal 'setc tank i ponent processes will be discussed in turn, followed by helminth eggs (figure 6-3). Whenever a septic tank IS adicsonfthefcsofaomletrtet desludged, it is inevitable that some portion of the a discussion of the effects of a complete treatment sludge will be fresh and, consequently, hazardous. Septic tank sludge should therefore be handled with great care and disposed of by burial, composting, or Pretreatment and primarY sedimentation digestion (either aerobic or anaerobic) in the same way Pretreatment by screening or comminution will have as any sewage sludge (and with the same effect on effetmentbyscreengcommmutionwage v pathgensseethe previous chapter and the following no effect on the pathogen content of sewage. pathogens-see the previous chapter and the following An almost universal first stage in conventional section). A well-designed aquaprivy, with a longer retention time (>20 days) than a septic tank, may sewagetreatmentisthesettligofsuspendedparticles produce an effluent with only low concentrations of enteric bacteria, protozoa, or helminth eggs, and many 2. See chapter 7, the section "Effluent Discharge. To ground- of the viruses may settle when adsorbed onto solids. It water." INFLUENT EFFLUENT Viruses ---------- - Viruses Bacteria A -Sptic - a-j- - Bacteria Sept ic tank with /-3 day retention time Protozoa _ .> Protozoa Helminths > Helminths Helminths Protozoa Bacteria Viruses SLUDGE Figure 6-3. Pathogen flow through a septic tank. HEALTH ASPECTS OF SEWAGE SYSTEMS 87 Pretreatment the theoretical settling velocities shown in table 6-1. + Actual settling velocities will be lower than these <0 Primary sedimentation figures because in actual sedimentation tanks many t factors hamper ideal settlement. The calculations Activated sludge or trickling filters indicate that only schistosomes, and maybe Trichuris, would have a reasonable degree of removal. Secondary sedimentation (humus tanks) Studies on laboratory and full-scale primary sedimentation tanks have been done, but laboratory models always give higher removal efficiencies than (Tertiary treatment ) actual plants because of more idealized and carefully t controlled conditions.3 Entamoeba histolytica cysts are Effluent discharge reduced by 50 percent or less. Between 35 percent and 98 percent of helminth eggs settle, with 50-70 percent Sludge digestion being the typical figure. Removal of various pathogens . from the effluent is as follows: Sludge drying Reduction (log1, unit) . Viruses 0-l Sludge disposal Bacteria 0-1 Protozoa 0-1 Figure 6-4. Components of conventional sewage Helminths 0-2 treatment in primary sedimentation tanks. A retention time in the Similar performance may be expected from secondary tankof26hoursis.A proportion of settlng tanks, except that these are often designed with tank of 2-6 hours IS normal. hihe overflowo rates. pathogens in the sewage will settle to the sludge layer hlgher overflow rates. either by direct sedimentation or by being adsorbed Flocculatlon of sewage (with ferrtc chlonde, lome, or onto solids that are in the process of settling. alum) will greatly improve the settlement of cysts and Many studies have found little or no virus removal eggs and perhaps of other pathogens as well. by primary sedimentation, and in actual treatment works a removal rate of 50 percent seems to be a Trickling filters maximum. Bacterial removal by primary sedimen- Trickling filters alone do not appear to be efficient tation may achieve 50-90 percent in 3-6 hours. in removing viruses from sewage. Reductions reported Shuval (1978) has collected data on the size and shape of eggs and cysts and has used these to compute 3. See Part Two, where the findings of such studies are reviewed. Table 6-1. Theoretical settling velocities of protozoal cysts and helminth eggs Characteristics of Cysts and Eggs Density Settling Size (grams per cubic Assumed velocity Pathogen (micrometers) centimeter) shape (meters per hour) Protozoa Entamoeba hartmanni 5 1.1 Spherical 0.007 Entamoeba histolytica 20 1.1 Spherical 0.11 Helminths Ascaris lumbricoides 55 x 40 1.11 Spherical 0.65 Hookwormsa 60 x 40 1.055 Spherical 0.39 Schistosoma spp. 150 x 50 1.18 Cylindricalb 12.55 Taenia saginata 30 1.1 Spherical 0.26 Trichuris trichiura 50 x 22 1.15 Cylindrical 1.53 Source: Adapted from Shuval (1978). a. Ancylostoma duodenale and Necator americanus. b. S. japonicum eggs are spherical. 88 HEALTH HAZARDS OF EXCRETA in the literature vary from 15 to 75 percent, with most protozoal cysts and helminth eggs, but substantial results indicating 30-40 percent removal.4 proportions of eggs will be removed in the secondary Reductions in indicator bacteria in trickling-filter settling tanks. Complete activated sludge treatment effluent vary between 25 and 99 percent. Typical plants have been reported to remove 80-100 percent of reductions appear to be 80-95 percent. Salmonella helminth eggs. reductions in the range of 71-99 percent are reported Considering the activated sludge process in isol- when removal by secondary sedimentation is included. ation, pathogen removal efficiencies may be sum- The lower the loading rate on the filter, the higher the marized as follows: bacterial removal. Many protozoal cysts and helminth eggs will pass Viruses Reductioni (log,( uirt) through trickling filters. Entamoeba histolytica removal Bacteria 0-2 of 83-99 percent has been reported. Egg removal Protozoa 0-1 appears to be in the range of 20-90 percent, with higher Helminths 0-1 reductions when the effect of secondary sedimentation is included. Removal of various pathogens by trickling filters is Sludge digestion as follows: It is clear from the discussion above that sludge from primary and secondary sedimentation tanks will Viruses Reduction g15 unit) contain a heavy load of excreted viruses, bacteria, Bacteria 0-2 protozoa, and helminth eggs. The fate of these Protozoa 0-2 pathogens depends on which of the many systems of Helminths 0-1 sludge treatment is adopted. Anaerobic sludge Several studies of trickling filters have examined digestion usually operates at one of three time- effluent after it has passed through a secondary temperature combinations: 13 days at 50°C, 28 days at sedimentation or humus tank. This tank may be 32°C, or 120 days unheated. The first stage is often expected to act as a primary sedimentation tank. followed by a second-stage settling or thickening Reductions in helminth eggs of 94-100 percent have process, in which the sludge stands for a time similar to been reported in combinations of trickling filters and that of the first stage to allow the supernatant liquor to humus tanks. be drawn off. If the digestion process is a batch process, thus Acririated sludge ensuring that all the sludge has been at temperature x for time y, the following pathogen removal perfor- Both laboratory data and field experience indicate mances at the specified time-temperature combinations that activated sludge systems are more effective in may be expected: removing viruses than trickling filters.5 Virus removals Coinntion Pathogens remoced in activated sludge treatment works have been 13 days at 50'C All reported as up to 90 percent, although better results 28 days at 32°C Viruses and protozoa: some bacteria (up to 99 percent) are achieved in laboratory or pilot- and many helminth eggs remain scale models. In poorly maintained activated sludge 120 days unheated Protozoa: persistent helminth eggs plants, the finding of low virus removal rates is not (in warm climate) (especially Asearis and Toenial and a of low virus removal rates is not ~~few bacteria and viruses remain unusual. Reductions of excreted bacteria are similar or a little better. Indicator bacteria removal rates are But if the digesters are worked as a continuous process, reported at up to 99 percent, but increases may occur, with sludge being added and removed daily or more Pathogenic bacteria removal rates are commonly frequently, it is not possible to guarantee retention reported as between 60 and 99 percent at normal t aeporati times (6-ween2 0 hours), but mayberasc as 9l times, and pathogen survival will be appreciably higher aeration times (6- t12 hours), but may be as high as 999 than indicated above. percent following extended aeration for Ž1 24 hours. The expected pathogen removal characteristics of The activated sludge process has little effect on sludge treatments, as well as the effect of subsequent sludge thickening, are summarized in figures 6-5 and 4. See Part Two for reports of pathogen removal by trickling 6-6.6 Protozoa will survive none of the digestion and filters. 5. Literature on the efficiency of activated sludge plants in 6. See Part Two for a review of the literature on pathogen survival removing excreted organisms is reviewed in Part Two. in sludge digestion. HEALTH ASPECTS OF SEWAGE SYSTEMS 89 DIGESTION THICKENING DEWATERING (CONTINUOUS) (CONTINUOUS) l SLUEdrying SLUDGE Viruses _ _1- _ _ _ _ _'_ _' (3months) >IHelminths Bacteria /3 days at /3 days _ Protozoa = - 50°C Helminths Ofher l l _ __ _ Lunheated - - Bacteria melhoos >Helminths SLUDGE |Sludge drying SLUDGE Viruses -- - --- ___ (3 months) > Helminths Bacteria 28o dcys at 28 days Protozoa s 32°C Helminths 1- i ------ Vactes unheate - Bacteric Methods Helminths SLUDGE Sludge drying SLUDGE Viruses -- months) Helminths Bacteria - ..120.dayse--;nthl Protozoa unhea/eday /20 days Helminths Other l I ~~~~~~~~~unheated l methods > Heiminths Figure 6-5. Pathogen flow throuigh various continuous sludge treatment processes thickening processes considered. Protozoal cysts are a possibly all, of excreted viruses and bacteria at warm feature of the effluents from conventional treatment temperatures (>20°C). Protozoal cysts will be de- plants and will not be found in treated sludges. With stroyed. Only persistent helminth eggs will survive in continuous operation, thermophilic digestion will significant numbers, especially those of Ascaris, leave small numbers of helminth eggs and excreted Trichuris, and Taenia.7 Other unheated dewatering viruses and bacteria, whereas 120 days of unheated processes-such as vacuum filtration, pressure digestion in warm climates will leave only helminth filtration, and centrifugation-will have little effect on eggs. The sole digestion process producing a pathogen content. thoroughly pathogen-free sludge is batch thermophilic digestion. Helminth eggs will always, and excreted Other sludge treatment processes viruses and bacteria will sometimes, be found in the sludges from all other digestion processes considered Sludge may be composted with refuse, sawdust, (Berg and Berman 1980). woodehips, bark, straw or other material added to provide carbon, lower moisture content and improve texture. Thermophilic composting can achieve excel- Sludge dewatering lent pathogen removal and is discussed in the previous Figures 6-5 and 6-6 also illustrate the effect of sludge dewatering on digested sludges. Drying sludge in open 7. The fate of various excreted pathogens during sludge drying is beds for 2-3 months will remove the great majority, reviewed fully in Part Two. 90 HEALTH HAZARDS OF EXCRETA DIGESTION (BATCH) THICKENING (BATCH) DEWATERING SLUDGE Sludge dr.ying Viruses (3 months) Bacteria - /3 days at /3 days Protozoa 50°C SLUDGE Helminths Ot I lOher l o~~~~~~~~~~nheated methods l l ~~~~~~~~~~~~~~~SLUDGE SLUDGE . P _ __SS/udg F drying Viruses (3 monthHelminths Bacteria -- _ 28 days elths Protozoa F 32 aCy 28 days Helminths Other - Bacteria vinheoted I methods Helminths l l ~~~~~~~~~~~~~~SLUDGE SLUDGE Sludge Viruses - d__lyb mnhs Hgin, Bacteria--- - 20 days Helminths Protozoa 12- unheated dS Hedminths I l I ~~~~~~~~~unheoted l l methods >> Helminths Figure 6-6. Pathogen flow through various batch sludge treatment processes chapter (the section "Composting"). Several other conventional sewage treatment can now be discussed.8 sludge treatment processes are in use or under First considered is a treatment plant featuring trickling experimentation, but most of them are too technically filters and primary and secondary sedimentation. complex and expensive to be appropriate for sludge The effluent from such a plant will contain treatment in developing countries. Those processes- significant concentrations of excreted viruses, bacteria, such as wet oxidation (heating under pressure), protozoa, and helminth eggs and is unsuitable for pasteurization, incineration and pyrolysis-that in- direct reuse in agriculture (see figure 6-7). It may often volve temperatures of 80°C or above-produce a be unsuitable for discharge to freshwater where such pathogen-free product (Osborn and Hattingh 1978). bodies of water are used without treatment for Sludge irradiation has attracted research interest and domestic water supplies by downstream populations. its effects on enteroviruses and fecal indicator bacteria The minimum retention time for liquids in the total are reviewed in chapters 9 and 13, respectively. plant may be around 5 hours, and this explains why the effluent-even if it is of adequate chemical quality (for Complete treatment works instance, the effluent might conform to the established The effect on pathogens of the unit processes having 8. The effect of conventional treatment plants on various been examined, the effect of their combinations in pathogens is reviewed fully in Part Two. HEALTH ASPECTS OF SEWAGE SYSTEMS 91 IN FLU ENT EFFWENT Viruses -----t _ ----- Viruses Bacteria - - Sewage treatment with ---- Bacteria primary sedimentation trickling filters, ond Protozoa = secondary sedimentotion Protozoa Helminths Helminths Helminths Protozoa Bacteria Viruses FRESH UNTREATED SLUDGE Figure 6-7. Pathogen flow through a conventionial sewage treatment plant featuring trickling filters physicochemical standard of <30 milligrams per liter quality from a health viewpoint is through certain of suspended solids and <20 milligrams per liter of tertiary treatment processes; even effluent chlorination standard biochemical oxygen demand, (BOD5)-will be may not be effective (see a discussion of both, below). of poor microbiological quality. Effluent quality may Effluents from activated sludge plants will be of be improved by using double filtration or recirculation, marginally better quality than those produced by but the final effluent will still be highly pathogenic. The trickling filters but will still be heavily contaminated only way to produce an effluent of reasonably good regardless of their chemical quality (see figure 6-8). The INFLUENT EFFLUENT Viruses --- --- XL- Viruses Bacteria -- Sewage treatment with Bacteria primary sedimentation activated sludge and Protozoa ~ secondary sedimentation Protozoa Helminths Helminths Helminths Protozoa Bacteria Viruses FRESH UNTREATED SLUDGE Figure 6-8. Pathogen flow through a conventional sewage treatment plantfeaturing actiuated sludge 92 HEALTH HAZARDS OF EXCRETA minimum liquid retention time in the plant may be illustrated in figures 6-5 and 6-6. From a health only 12 hours, and the final effluent will contain viewpoint, the object of a sewage treatment works significant numbers of any pathogen found in the raw should be to retain all solids and liquids for the sewage. Tertiary treatment is indicated prior to reuse maximum time or to heat them to the maximum or prior to discharge into a river that downstream temperature feasible, or both. Batch processes are far populations are using for water supplies. more reliable in achieving this than continuous The microbiological quality of the sludge depends processes, and thought must be given to the design and on what treatment it receives. Fresh sludges from economics of batch digesters in circumstances where primary and secondary sedimentation tanks will sludge is to be reused in agriculture. contain pathogens of all kinds. Digestion at 50°C for 13 days will kill all pathogens, and digestion at 32°C for 28 days will remove protozoa and enteroviruses, provided Aerated Lagoons that a batch process is used in both instances. Digestion for 120 days without heat in warm climates Aerated lagoons resemble small waste stabilization will remove all pathogens except helminth eggs, also ponds with floating mechanical aerators, but they are only if a batch process is used. Continuous addition more correctly considered as a simple modification of and removal of sludge will allow pathogens to pass the activated sludge process. Reference to the section through all processes. Sludge drying for at least 3 on activated sludge earlier in the chapter and to the months in a warm climate is highly effective against all section on stabilization ponds below, along with the pathogens except helminth eggs. Other unheated description here, will clarify the specifics of this system. dewatering techniques have little effect on the pathogenic properties of sludge. The illustration of this somewhat complex situation Technical description in figures 6-5 and 6-6 shows that only a batch digester In aerated lagoons screened rather than settled operated at 50°C will produce a pathogen-free sludge. sewage is aerated, and there is no sludge return (see Continuous digestion (as in practice) at 50°C may figures 6-9). Retention times for domestic sewage are produce a sludge with excreted viruses and bacteria typically 2-6 days and lagoon depths are 2-4 meters. and helminth eggs if sludge drying beds are not used. The effluent from the lagoon contains 200-500 All other alternatives will produce a sludge containing milligrams per liter of suspended solids (activated helminth eggs and some (such as mesophilic digestion sludge flocs) and therefore requires further treatment followed by vacuum filtration) will produce a sludge either in an ordinary secondary sedimentation tank with excreted viruses and bacteria as well. (retention time: 2 hours, minimum) or in a settling The importance of temperature and time is clearly pond (retention time: 5-10 days). The latter is more Sedimentation tank Sewage -* ( Loon Effluent Sludge Digester Disposal Drying beds Figure 6-9. Flow diagran jbr an aerated lagoonl incorporating siludge digestion. From Mara (1976) HEALTH ASPECTS OF SEWAGE SYSTEMS 93 F M M Stoge I Sewoge_ -0 Stage 2 Aerator Stcige 3 gX_ Figure 6-10. Stages in development of a waste stabilization pond-aerated lagoon system. F. Facultative pond; M maturation pond; A anaerobic pond; AL aerated lagoon. At stage 3 additional maturation ponds will probably be necessary. In some cases septic tanks may replace anaerobic lagoons (usually for populations below 10,000) advantageous because it is often cheaper, easier to however, be treated in one or more maturation ponds maintain, and more efficient in terms of removal of to achieve any desired level of pathogen survival. excreted pathogens. Aerated lagoons are often used to extend the capacity of existing waste stabilization pond systems (see figure 6-10). Oxidation Ditches Pathogen survival In addition to the aerated lagoon, the oxidation ditch is another modification of the activated sludge In the aerated lagoon itself there will be incomplete process. removal of excreted pathogens, although as a result of the longer retention times the removal achieved is Technical description better than that obtained in the conventional activated sludge process. In the settling pond there will be Screened sewage is aerated in, and circulated complete removal of excreted protozoa and helminth around, a continuous oval ditch by one or more special eggs, but schistosome and hookworm larvae may aerators (called "rotors") placed across the ditch (see appear in the effluent, which will also contain figure 6-11). The ditch effluent is settled in a pathogenic bacteria and viruses. The effluent may, conventional secondary sedimentation tank, and Rotor\ Ditch Sewage Effluent 1 Sludge Drying beds Figure 6-11. Flow diagranifo7 an oxidation ditch. From Mara (1976) 94 HEALTH HAZARDS OF EXCRETA almost all the sludge ( > 95 percent) is returned to the the effluent may be reduced but not substantially, and ditch. The small quantity of excess sludge is placed probably insufficiently to justify investment in this directly on sludge drying beds. The hydraulic retention filtration method by the health benefits it yields. times are 1-3 days in the ditch and 2 hours, minimum, in the sedimentation tank. Because a high proportion of the sludge is recycled, the mean retention time for Slow sandfiltration solids is 20-30 days; as a result there is only a small This method may be used in small treatment works. production of excess sludge, which is highly mineralized The low loading rates of the filters (2-5 cubic meters and requires only dewatering on drying beds. The main per square meter daily) causes them to occupy a large engineering advantages of the process are that primary land area. Substantial biological activity builds up, sedimentation is eliminated and that sludge produc- especially in the upper layers of the filter, and pathogen tion and treatment are minimal. removal may be very high. Removal of 4 log,10 units of excreted viruses and bacteria may be expected from a Pathogen survival well-run unit, with virus removal a little higher than bacteria removal. Complete retention of protozoal The effluent from the sedimentation tank has a cysts and helminth eggs has been recorded. Slow sand pathogen content similar to that of the effluent filters are therefore highly effective in removing produced by a conventional activated sludge process, pathogens from a secondary effluent, but their land although as a result of the increased retention time requirement makes them suitable only for small slightly lower survivals are achieved. The small treatment works. quantity of sludge produced is similar in quality to that produced by an anaerobic digester and contains the Land treatment same range of excreted pathogens. Secondary effluents may be applied to land in three ways; application to land for deep percolation and Tertiary Treatment groundwater recharge, application to land for col- lection in underdrains, and application to sloping grass Tertiary treatment methods are increasingly used in plots for collection in downslope channels. The first Europe and North America to improve the quality of two systems can have extremely high pathogen effluent produced by conventional treatment works. removal performances,l" whereas the grass plot system Sophisticated systems designed to reclaim effluent for is less effective because some of the effluent runs over potable water, such as the one used at Windhoek, the surface of the soil, rather than through it. There is Namibia (Stander and Clayton 1977), are not intended little or no information about the application of these by the term, but rather those treatment processes used processes in the tropics or in developing countries. If to upgrade the physicochemical quality of an effluent poorly managed, they will probably lead to the prior to discharge. Tertiary treatment processes creation of a foul and unsanitary bog. In addition, all originally were not designed primarily for pathogen land application systems pose the potential threat of removal, but some of them do have good pathogen groundwater contamination. removal characteristics.9 Maturation lagoons Rapid sanidfiltration Conventional effluents can be upgraded in matur- This is perhaps the most common tertiary treatment ation lagoons. The principles involved are exactly as found in larger treatment works. High loading rates described for waste stabilization ponds (see the section (200 cubic meters per square meter daily) and frequent of that title, below, and figure 6-10). If two or more backwashing (1-2 days) prevent the build up of much maturation ponds are used, with perhaps 5 days of biological activity in the filter. Some viruses will be retention in each, total removal of protozoal cysts and adsorbed to solids and some bacteria retained. helminth eggs will be achieved. High levels of virus and Protozoal cysts and helminth eggs may be retained because of their size. In short, the pathogen content of 10. See chapters 9 and 13 and Uiga and Crites (1980). 9. The effect of tertiary processes in removing excreted pathogens 11. See chapter 7, the section "Effluent Discharge. To ground- from secondary effluents is reviewed in Part Two. water." HEALTH ASPECTS OF SEWAGE SYSTEMS 95 bacteria removal are also effected, and a pathogen-free the effluent are affected by the chlorine, many of which effluent may be produced by adding sufficient ponds. are essential for the effluent's natural self-purification. If the effluent is discharged into a river or lake, the chlorine may adversely affect the ecology of the Other tertiary treatment processes receiving water and hinder its natural oxidation Several other tertiary treatment processes are in use processes. Further, the chlorine will be present in such or under experimentation, including coagulation, forms as chlorinated organic compounds, which are carbon adsorption, irradiation, and ozonation. The less biodegradable than their parent compounds and effects of these on enteroviruses and fecal indicator are directly toxic to fish and other aquatic life (Water bacteria are reviewed in chapters 9 and 13. These Research Centre 1979). processes are, in general, too technically complex and Excreted viruses are more resistant to chlorination costly to be appropriate for sewage treatment in than bacteria.13 Chlorine doses of 30 milligrams per developing countries. liter and above have been recommended; even so, complete viral removal may not be achieved (Melnick, Gerba, and Wallis 1978). It appears, at least from Effluent Chlorination South African experience (Nupen, Bateman and McKenny 1974), that chlorination beyond the The chlorination of sewage effluents is commonplace breakpoint-with resultant free, residual chlorine as in only a few countries (notably the USA, Canada, and HOCI-may be necessary to effect viral removal. Israel). Its purpose is to reduce the pathogen content of Depending on the chlorine demand and pH of the conventional effluents. As discussed earlier, it repre- effluent, breakpoint chlorination may require high sents the borrowing from the water treatment industry doses and will always require efficient and vigilant of a technology that might overcome the poor process control. pathogen removal characteristics of conventional It is most unlikely that chlorination of effluents will treatment systems."2 Effluent chlorination has a be effective in eliminating protozoal cysts because they number of serious limitations, the principal one being are more resistant than either excreted viruses or that in some senses it does not work. At best, bacteria. Most helminth eggs will be totally unharmed chlorination is complex and difficult to control. by effluent chlorination. Chambers (1971) writes that It is evident from these shortcomings that effluent chlorination may not be particularly effective in Chlorination of wastewater effluents iS a vastly more rmvn ahgn rmcnetoa flet.Ta complex and unpredictable operation than chlori- removing pathogens from conventional effluents. That nation of water supplies. It is extremely difficult to maintain a high, uniform, and predictable level of consequences-including the proliferation in water disinfecting efficiency in any but the most efficiently supplies of carcinogenic chlorinated hydrocarbons, diecatingwast treffiien nt panytbu themosteffiently which are formed by the reaction of chlorine with organic material-must also be considered (Buxton For these reasons it should be rejected except where the and Ross 1979; Carlo and Mettlin 1980; Deinzer, highest levels of management and process control are Schaumburg, and Klein 1978; Grabow 1979; Hais and guaranteed. Venosa 1978; Wilkins, Reiches, and Kruse 1979). Chlorine has to be applied in heavy doses (10-30 Nupen and Morgan (1978) write, regarding effluent milligrams per liter) to achieve coliform concentrations chlorination below the breakpoint in South Africa, of less than 100 per 100 milliliters of effluent. These that levels of chlorine will also kill pathogenic bacteria if the chloinedemnd o th efluen isnottoo igh ifthe Present findings indicate that the practice not only chlorine demand of the effluent isre ot well hixedh if th fails to provide an effective barrier to the spread of chlorine and the effluent are well mixed, and if diseases but ignores the environmental impact on adequate contact time (at least 1 hour) is allowed. But receiving waters ... Under no conditions can this regrowth of coliforms and Escherichia coli following type of chlorination be considered as a substitute for chlorination has been widely reported (for instance, Shuval 1977), and the regrowth of pathogenic bacteria the adequate treatment of wastes. has not been fully ruled out. Moreover, all bacteria in 12. See chapter 4, the section "Objectives of Night Soil and 13. Inactivation of enteroviruses and fecal indicator bacteria by Sewage Treatment." effluent chlorination is reviewed in chapters 9 and 13. 96 HEALTH HAZARDS OF EXCRETA Waste Stabilization Ponds normally be used in conjunction with one another to form a series. Although it is all too common to find only a single facultative pond treating domestic wastes, Waste stabilization ponds are the most economic this represents a false economy when health is method of sewage treatment wherever land is available considered.Mtura pondsyare ne arto es at~~~~~~~~~~~~~ reaieylwcs Mig n ed17) hs considered. Maturation ponds are necessary to ensure e. T low pathogen survivals. Good designs (see figure 6-10) they are widely used in North America. But their incorporate a facultative ond and two or more principal advantage in warm climates is that they paturation pond astes orhmore maturation ponds; for strong wastes (biochemical achieve low survival rates of excreted pathogens at a . . much lower cost than any other form of treatment, with of anaerobic ponds as pretreatment units ahead of maintenance requirements simpler by several orders of facultative ponds is often advantageous because they magnitude. In fact, a pond system can be designed to minimizvhe land requirements of the whole pond ensure, with a high degree of confidence, the total mi elimination of all excreted pathogens. This is not system usually achieved in practice because the incremental benefits resulting from achieving zero survival, rather Pathogen survival than low survival, are less than the associated Several authors have reported the fate of fecal incremental costs. Yet waste stabilization ponds are indicator bacteria in ponds (see chapter 13)i4 High the best form of treatment in tropical, developing removal rates of 99.99 percent or better have been countries because they can achieve any level of reported for series of three, four, or more ponds. pathogen removal desired. From a strictly health- reported elimination of Salmour, or o ther directed viewpoint, the fact that ponds can do this at Cmlt lmnto fSloel n te directed viewpoint, thenteropathogenic bacteria can be achieved in pond lowest comparable cost is an additional advantage. systems with long retention times (30-40 days), particularly if ambient temperatures are above 25°C Technical description (see chapters 13 and 15). It is known from both Waste stabilization ponds are large, shallow ponds theoretical considerations and field experience that a in which organic wastes are decomposed by micro- series of ponds will perform far better in removing BOD organim in waste a re dcombination posed na l proes and excreted bacteria than will a single pond with the organisms in a combination of natural processes sm vrl eeto ie eiso iet ee invotving both bacteria and algae. The waste fed into aof five to seven stabilization pond system can be raw sewage, ponds, each with a retention time of 5 days, can aquaprivy effluent, or diluted night soil (figure 6-10). produce an effluent containing 100 fecal coliforms and There are three kinds of ponds in common use: fecal streptococci per 100 milliliters. Such an effluent can be safely used for unrestricted irrigation. Little is known at present about the fate of viruses in * Anaerobic pretreatment ponds, which function ponds in warm climates or developing countries (see similarly to open septic tanks; they have retention chapter 9). Viruses adsorb to solid particles that may times of 1-5 days and depths of 2-4 meters. settle to the sludge layer, and other biological and c Facultative ponds, in which the oxygen necessary physical factors may be specifically virucidal; for for biooxidation of the organic material is supplied instance an increase in pH to Ž. 9 caused by blooms of principally by photosynthetic algae, which grow algae. Irrespective of such effects, inactivation of naturally and with great profusion in them; they excreted viruses will proceed rapidly in warm waters, have retention times of 10-40 days and depths of and may be 1-2 log units per 5 days in ponds at 1-1.5 meters. > 25°C. A pond system with an overall retention of 30 C Maturation ponds, which receive facultative pond days in a warm climate should therefore achieve a effluent and are responsible for the quality of the reduction of excreted viruses of not less than 6 log final effluent; they have retention times of 5-10 units (99.9999 percent). days and depths of 1-1.5 meters. Reports on the effect ofponds on protozoal cysts and helminth eggs (see chapters 20 and 23) indicate 100 percent removal in all cases in which well-designed, Anaerobic and facultative ponds are essentially multicelled ponds with a total retention time of > 20 designed for biochemical oxygen demand (BOD) removal, whereas the function of maturation ponds is 14. A compilation of original sources and findings on pathogens the destruction or removal of excreted pathogens. in waste stabilization ponds is given in Part Two, especially chapters These three ponds are complementary and should 9, 13. 20. and 23. HEALTH ASPECTS OF SEWAGE SYSTEMS 97 days were investigated. Hookworm larvae may survive supervised staff of laborers who should be employed on for up to 16 days in aerobic ponds. Because of this fact, all waste stabilization pond plants. Mosquito breeding hookworm larvae have been reported in the effluent in ponds can thus be largely circumvented by good from ponds with an overall retention time of < 10 days; design and good maintenance. they have not, however, been reported in the effluent of In summary, well-designed pond systems- ponds with retention times of > 20 days. The majority incorporating a minimum of three cells, and having a of schistosome eggs in an aerobic pond will settle; in a minimum total retention time of 20 days (see figure 6- facultative pond they will either settle or hatch into 12)-produce an effluent that will contain only small miracidia. Miracidia will either die or infect an concentrations of excreted bacteria and viruses. intermediate snail host if the correct snail species is Excreted helminth eggs and protozoal cysts will be colonizing the pond (as may be the case in badly completely eliminated. Bacterial or viral pollution can maintained and vegetated ponds). Even if cercariae be further reduced (or eliminated) by adding more emerge, they should not find a human host to invade ponds to the system. The effluent is suitable for direct and will die within 48 hours. reuse or discharge into receiving waters. An important consideration in the design and operation of waste stabilization ponds is that they may become sites for mosquito breeding. The most Literature Cited common mosquitoes found breeding in ponds belong to the Culex pipiens complex, which favors polluted Berg, G. and Berman, D. (1980). Destruction by anaerobic water. The distance between the town producing the mesophilic and thermophilic digestion of viruses and indicator bacteria indigenous to domestic sludges. Applied sewage and the pond system treatingsit ishusay we and Environmental Microbiology, 39, 361-368. withinthe flight range of the mosquitoes,whichmaybe Buxton, G. V. and Ross, S. A. (1979). Wastewater as great as 10 kilometers. Any large outbreak of disinfection-toward a national policy. Journal of the mosquitoes will thus be a nuisance (depending on the WVater Pollution Conitrol Federation, 51, 2023-2032. weather conditions at the time). Moreover, because the Carlo, G. L. and Mettlin, C. J. (1980). Cancer incidence and mosquitoes can serve as vectors for disease, it is trihalomethane concentrations in a public drinking water essential to attempt to keep waste stabilization ponds system. American Journal of Public Health, 70, 523-525. free of mosquitoes. Studies on mosquitoes in ponds Chambers, C. W. (1971). Chlorination for control of bacteria (reviewed in chapter 36) indicate that emerging and and viruses in treatment plant effluents. Journal of the encroaching vegetation are important in encouraging Water Pollution Conttrol Federation, 43, 228-241. breeding. It is easy in practice to discourage vegetation Deinzer, MI., Schaumburg, F. and Klein, E. (1978). growth in ponds by making the ponds > 1 meter deep Environmental Health Sciences Center Task Force review growth inpndsing thcreteslabs,rip , pondsoi cementen dhee of halogenated organics in drinking water. Envir-onmiental and usmg concrete slabs, rip-rap, or soll cement on the Health Perspectives. 24, 209-239. embankments at the surface water level. Reinforcing Grabow, W. 0. K. (1979). Disinfection of water: pros and the pond's banks not only prevents vegetation from cons. Water South Africa, 5, 98-105. growing down the embankment but also halts erosion Hais, A. B. and Venosa, A. D. (1978). EPA overview of of the embankment by wave action. Any residual municipal wastewater disinfection. Joturnal of tlte Wiater vegetation problem may be dealt with by the well- Pollution Conttrol Federation, 50, 2470-2476. INFLUENT EFFLUENT Viruses ----__ _ -----e- Viruses Waste-stcabi/&ictibn ponds Bacte ria *- 6 teristics similar to this hypothetical example (Cohen months). Their removal from effluent will require and others 1971). either the use of waste stabilization ponds or tertiary treatment in the form of sand filtration, land Foodstuffs for animal consumption application, or lagooning. Removal of Taenia eggs from sludge requires either a thermophilic process or A widespread use of sewage effluents, sludge, and retention for over a year. T saginata infection in night soil is in application to pastures or fodder crops humans is not a major public health problem in most subsequently fed to animals. In the United Kingdom, countries. The importance of controlling the infection for instance, 74 percent of all sewage works sludge is lies in its consequences for the beef industry. Carcasses disposed of on land, the remainder dumped at sea. Of found to contain the cysts of T saginata are condemned the sludge disposed of on land, 21 percent is spread on in whole or in part and the economic loss is substantial grazing land, 35 percent on general arable land, 33 in areas of high transmission. percent is dumped, and the remainder is used in horticulture, forestry, and land reclamation. Of the SALMONELLOSIS. Sewage effluents, sludges, and sludge applied to grazing land, 29 percent is applied night soil from all large communities in both rich and raw and 71 percent is applied following digestion poor countries will contain substantial numbers of (Standing Committee on the Disposal of Sewage salmonellae. Figures of 104 organisms per liter of raw Sludge 1978). A wide variety of animal pathogens may sewage and of raw sludge are not uncommon in be encountered in sewage sludge, and night soil, Europe. These salmonellae may reach pastures or including: fodder crops and may infect animals and animals may subsequently infect people. The infective doses Viruses causing: Bacteria causing: Helminths calusing: required are high, however, and Salmonella infections Foot and mouth Anthrax Beef tapeworm are transmitted among cattle by many ways other than disease Brucellosis infection contaminated fodder. There is no clear evidence that Porcine Leptospirosis Pork tapeworm cattle grazed on pastures fertilized with wastes are at encephalomyelitis Salmonellosis infection Rabies Tuberculosis more risk from salmonelloses than other cattle (see Rinderpest chapter 15). Swine fever TUBERCULOSIS. Wastes from institutions treating tuberculosis patients, or from industries such as dairies HEALTH ISSUES. Despite this alarming array of and abattoirs that handle tuberculous animals, will infections, it is clear that, in most cases, the sewage or almost certainly contain Mycobacterium tuberculosis. sludge will contain an insignificant number of these Studies in Denmark (Jensen 1954) showed tubercle pathogens and will have a negligible effect in transmitting these diseases. There are three exceptions, . Pork tapeworm (Taenia solium) infection has been omitted ' from this discussion because, although the use of human wastes on however,,in whic the use of huma wastesonpastres fodder crops fed to pigs would undoubtedly promote the or fodder crops may promote the transmission of transmission ofthis helminth, in practice its life cycle usually depends diseases of significant human or veterinary impor- on pigs gaining direct access to human feces, which they eagerly eat. 102 HEALTH HAZARDS OF EXCRETA bacilli in the sewage produced by 5 towns with elsewhere, of using effluents to irrigate parks, lawns, tuberculosis sanatoria. Tubercle bacilli were also central concourses or medians of highways, and other demonstrated in the effluent, digested sludge, and 5- open amenity areas. Effluents are sometimes brought week-old dried sludge from the treatment plants olthese in tankers from the treatment works to the city center towns. for this purpose. Where conventional treatment works Chlorination will remove tubercle bacilli from without tertiary processes are operating, this practice sewage effluent, although they are more resistant than involves great risk to the public health and should be Escherichia coli. In one experiment an applied dose of condemned. It is only acceptable to use the effluents 10 milligrams per liter of chlorine removed tubercle from waste stabilization pond or tertiary treatment bacilli from an effluent having a BOD5 of 11-63 processes and, even then, very careful monitoring ofthe milligrams per liter (Jensen 1954). Greenberg and pathogen content in these effluents is required. Kupka (1957) concluded, however, that a chlorine dose Compared with other reuses described in this chapter, of 20 milligrams per liter and a contact time of at least 2 the irrigation of amenity areas is a high-risk activity. hours were required to remove tubercle bacilli from a well-oxidized effluent. Sludge has been recorded as containing at least 7 x 105 tubercle bacilli per gram of Occupational hazards dry matter (Heukelekian and Albanese 1956), and 15 A health hazard common to all the agricultural reuse months on a drying bed were required to remove these practices considered above is the risk to those who in Denmark (Jensen 1954). Sludge may also be actually work in the fields. Although there is very disinfected by thermophilic processes, in which limited epidemiological evidence to demonstrate the tubercle bacilli are killed after 20 minutes at 66°C. fact, it is likely that those who work in fields In summary, tubercle bacilli may be numerous in contaminated by excreted pathogens are at greater risk sewage, sludge, and night soil, and they are more than others. If fieldworkers bring these infections back persistent and resistant to disinfection than the enteric into their homes and subsequently infect their families, bacteria. The epidemiological significance of this is then a measurable difference in their health compared unclear. There is a case reported of tuberculosis in with that of nonagricultural workers and the whole children who fell into a river polluted by sanatorium community may not be apparent. Moreover, in many wastes (Jensen 1954). It remains most doubtful, agricultural communities practically the whole popu- however, that transmission of either human or bovine lation works in the fields at some time of the year, and tuberculosis is significantly affected by exposure to so all may be exposed to the risk (although not wastes or polluted water.2 equally). The only sure way to protect the health of the Other agricultural products agricultural workers is to use only wastes that are pathogen free or nearly so.3 Once again this means Fecal wastes may also be used to produce crops not only effluents that have undergone waste stabilization intended for consumption by animals or humans. pond or conventional treatment followed by land Examples are tree cultivation for timber production, application, sand filtration, or lagooning. Similarly, beautification, or the control of desertification; the sludges or night soil require batch thermophilic irrigation of parks; and the cultivation of commercial processing, protracted drying, or storage for over I crops such as cotton or coconuts (Sundaresan, year. Muthuswamy and Govindan 1978). These reuse A special problem affecting the health of agricultural technologies pose health hazards mainly of an workers is spray irrigation using sewage effluent. occupational kind. Workers in the fields and in the Aerosol droplets containing excreted viruses and factories where the crops are processed are at risk (see bacteria may travel several hundred meters downwind, the next section). and excreted bacteria may be more infective (that is, One reuse system worth special mention is the have a lower infective dose) when inhaled than when practice, now widespread in the Middle East and 3. This recommendation, with some others in Part One of this 2. Tuberculosis has not been considered in Part Two. Those book, concerns ideal practice and is directed to those contemplating wishing to read further may consult Greenberg and Kupka (1957); the establishment of new waste treatment and reuse projects. For Heuke1ekien and Albanese (1956); Jensen (1954); Maddock (1933); those trying to upgrade existing systems, it should he noted that any Pramer, Heukelekien and Ragotzkie (1950); Viraraghavan and measurable reduction in the pathogen content of a waste is likely to Raman (1967); and Williams and Hoy (1930). improve public health. EXCRETA REUSE AND EFFLUENT DISCHARGE 103 otherwise ingested.4 There is therefore some cause for Pathogen control in agricultural reuse concern that aerosol-disseminated excreted viruses and acteia an ifec, byinhaatin, tosewho ork There is now a substantial literature on the health and bacteria can infect, by inhalation, those who work implications of the agricultural reuse of excreta, much in, or live near to, spray-irrigated fields. A quite of which is reviewed in Part Two. Several reviews of the different potential hazard of spray irrigation is that it topic, which some readers may find of additional value, often causes ponding of effluent, and this might lead to ar6lso alable.f increased populations of Culex pipiens, and other are also avarlable d mosquitoes breeding in dirty water (Sorber and Guter It is clear from the dwscusslon above that a desirable 1975). public health policy would be to require the highest A study in Israel (Katzenelson, Buium, and Shuval quality standards for all wastes reused in agriculture. 1976) showed that people in kibbutzim (cooperative For effluents, this standard might be expressed in terms agricultural settlements) practising spray irrigation of a fecal coliform count of less than 100 per 100 . . . . ~~~~~milliliters (World Health Or anization 1973). Such a with waste stabilization pond effluent had a higher g incidence of shigellosis, salmonellosis, typhoid, and standard, however, may tell little about the effluent infectious hepatitis than people in kibbutzim practis- content of viruses, protozoa, and helrrinth eggs, ing no form of wastewater irrigation. This could be especially following the chlorination of the effluent, a attributed either to the agricultural use of wastewater process considerably more lethal to excreted bacteia or specifically to the spray technique promoting than to other excreted pathogens (see the previous aerosol transmission. Subsequent debate, and new chapter). As discussed in chapter 4, E. coli is also an studies in Israel (Shuval and Fattal 1980), have cast inappropriate indicator for the quality of treated doubt on tsfsludges or night soil. For these materials the doub on hesefindngs Thee isno cncluive concentration of Ascaris eggs is a better guide to epidemiological evidence of adverse health effects overathon cnet7 Criteisa for Acis hv caused by exposure to wastewater aerosols at spray overall pathogen contenta CrGtera for Ascaris have irrigation sites or sewage treatment plants (Pahren and 1978). Jakubowski 1980). Such health effects, if they do exist, 1978). are less likely in dry, sunny climates than in temperate Teipsto fsrnetqaiysadrso arealess lelys vin y sunny baclteshan in tempere effluents (for example, < 100 fecal coliforms and fecal climates because viruses and bacteria in aerosols are stetooc pe 10 millies retit.herneo rapidly inactivated by warm temperatures, low streptococci per 100 mlliliters) restricts the range of humidit an brig sunlight.5 treatment technologies considerably. It is fortunate humpeidity ig h i that waste stabilization ponds are able to meet these A specific occupational hazard in the agricultural stnadadaralo-s,aporiefrm f reuse of excreta is schistosomiasis. Of the various standards and are a low-cost, appropriate form of species, the one whose transmission has been related to waste treatment in hot climates (see chapters 4 and 6). deliberate reuse rather than incidental pollution is Irrigation with waste stabilization pond effluent is Schistosoma japonicum. The eggs survive in feces for therefore recommended. The imposition of strict quality standards on sludges over a week, so that when excreta are applied fresh to irrigated rice fields containing the amphibious snail or night soil (< 10 viable Ascaris eggs per 100 grams, hosts, the snails may become infected. This occurs in for example) poses greater problems. Such standards several parts of Southeast Asia and, most notably, in can only be achieved by well-managed thermophilic China. After the schistosomes have developed within digestion or composting, or by retention times of > 1 the snails, larvae that can bore through the human skin year. A second-best choice, as indicated in figure 6-6, areshedintothewater, thus creatingtheoccupational would be batch mesophilic digestion followed by are~~~ ~ she inotewtr.hsceaigteocptoa several months on drying beds. An alternative for night risk to farmers. The snail-transmitted larvae of other seue isnts os in A altative stabizt flatworms encyst on vegetables or in fish and crabs, so soil reuse is its deposit in a facultative stabilization that they infect the consumer rather than the pond to produce a small effluent flow for irrigation or agricultural worker. Excreta can be rendered free of fish farming. live schistosome eggs by suitable treatment (see 6. See, for instance Benarde (1973): Bryan (1977); Burge and chapter 32). Marsh (1978); Crook (1978);Engelbrecht (1978); Gerba, Wallis and Melnick (1975); Goldberg (1979); Hickey and Reist (1975); Pahren and others (1979); Petrik (1954); Rudolfs, Falk and Ragotzkie (1950 4. Enteroviruses and fecal indicator bacteria in aerosol droplets and 195i a f); Shuval (1977); Sorber and Guter (1975); Sorber and are discussed fully in the relevant sections of chapters 9 and 13. Sagik (1978); Wiley (1962); Wiley and Westerberg (1969) and World Health Organization (1973). 5. The costs of alternative methods of reducing any health hazards associated with spray irrigation are reviewed by Young (1980). 7. See Chapter 4, the section "Pathogen Indicators." 104 HEALTH HAZARDS OF EXCRETA In conclusion, stringent quality standards may be set In addition to promoting productivity, growing fish upon waste intended for agricultural reuse, and these in waste-enriched ponds has other advantages. With standards can be achieved by relatively simple and low- reference to sewage treatment, nutrient removal is cost technologies. Major problems in pathogen improved because nitrates and phosphates concentrate removal will only be encountered where conventional in the food chain and are thus removed during sewage treatment plants are in use. Such plants harvesting of the fish (Wert and Henderson 1978). The produce both an effluent and a sludge that are rich in bacteriological quality of the sewage may also improve pathogens and that require expensive additional because the presence of fish appears to raise the oxygen treatment (see the previous chapter) before they can be levels and the pH (generally, to over 8.5) of the ponds, recommended for unrestricted agricultural reuse. and both of these effects increase the death rate of enteric bacteria. Furthermore, there is some evidence that fish reared in sewage are less prone to disease than Reuse in Aquaculture others. Human excreta may be reused to promote the HEALTH ISSUES. There are three distinct health growth of aquatic flora and fauna, a practice known as problems associated with fish farming in excreta- aquaculture. Three principal kinds of aquaculture are enriched ponds: common: fish farming, algae production, and mac- . P rophte (acrocopc aqaticplat) poducion* Passive transference of animal pathogens by fish rophyte (macroscopic aquatic plant) production. contaminated by polluted water. * Transmission of helminths whose life cycles involve Fish lfrming fish as intermediate. host. The raising of fish in ponds enriched with human * Transmission of other helminths with life cycles and animal excreta has a long tradition. In China and inmvolvmg other pond fauna, such as the snal elsewhere in Asia it has been operating continuously for centuries; it was practised in ancient Egypt and was The first of these problems is a cause for concern widely used by European monasteries in the Middle throughout the world, whereas the second and third Ages. apply only in areas where particular eating habits are The controlled addition of wastes to ponds causes a found, where the helminths concerned are endemic, or large population of bacteria to thrive; these organisms both. in turn promote communities of phytoplankton (algae) and zooplankton, which then graze on the algae. With PASSIVE TRANSFERENCE OF EXCRETED this rich food chain available, some fish, notably carp PATHOGENS. Fish may passively carry excreted human and tilapia, grow rapidly. Different fish species pathogens in their intestines or on their body surfaces, occupy different ecological niches-some feeding on and these pathogens may subsequently infect people large algae, some on small algae, some on zooplankton, who handle, prepare, or eat these fish. There is little risk some in the bottom layers, and some nearer the surface. to fish eaters except in areas where fish are eaten raw or For this reason, polyculture (the growing of several partially cooked. Thorough cooking will destroy all species in the same pond) is widely practiced excreted pathogens. The risk to those who handle or (Muthuswamy and others 1978) because it greatly prepare the fish, however, is unaffected by the local increases the total fish yield. eating habits. Fish may be grown in ponds enriched with sewage or Most studies on pathogen carriage by fish are night soil. Where sewage is used, it is usually related to fish caught in sewage-polluted seawater or pretreated, diluted, or both. An appropriate system is rivers, but the principles of pathogen carriage will to grow fish in the maturation ponds of a chain of waste apply to fish farming as well. There is abundant stabilization ponds (seefigure6-lO);fish (except theair- evidence that the intestinal bacteria of humans and breathing varieties) cannot be grown in facultative animals are not the normal resident flora of fish. Fish ponds because the biochemical oxygen demand (BOD) raised in contact with these bacteria may, however, may exceed the oxygen supply. with the result that the acquire substantial numbers of them on their bodies water becomes deoxygenated, and the fish die. Night and in their intestines. Fecal coliforms, fecal streptoc- soil is commonly added to ponds either by locating occi, and salmonellae are easily isolated from fish latrines directly over them or by delivering night soil to grown in polluted waters. A concentration effect is them in carts or trucks. discernible, and concentrations of enteric bacteria in EXCRETA REUSE AND EFFLUENT DISCHARGE 105 fish intestines tend to be higher than in the water in preservative and pickling techniques for fish have little which the fish live. There is even evidence of their effect (see chapter 24). ability to multiply in the intestines of some fish (see Where fish are grown in pretreated or presettled chapters 13 and 15). sewage, Clonorchis eggs will have settled. Transmission It is quite possible for pathogenic bacteria carried by is therefore associated with the direct enrichment of fish in this way to infect people. It is equally possible for ponds with night soil or raw sewage. Clonorchis eggs the contaminated fish to infect (especially with are fragile and die if stored for a few days in night soil. Salmonella) the animals fed on fishmeal and the people Seven-day storage of night soil prior to pond who eat these animals. In practice, however, it is enrichment is therefore a sound strategy for the control equally likely that the fish will become infected after of this infection, but it must be noted that this helminth harvesting and during handling, transport, and has other vertebrate hosts (such as dogs and cats) processing (Brown and Dorn 1977). The major besides man and that the control of human excreta may outbreaks of salmonelloses in animals and man known only partially reduce transmission. to be associated with fish have been associated with contamination after harvesting. It remains quite HELMINTHS WITH OTHER AQUATIC INTERMEDIATE possible for fish to carry bacterial pathogens passively HOSTS. Third, it is possible that schistosomiasis from enriched ponds to humans and thereby to cause transmission through the presence of the approp- infection. The survival of excreted bacteria in fish riate species of snails as intermediate hosts-may entrails or in fish transferred to clean water is generally occur in the ponds and infect fishermen. This requires reported as less than 14 days (see chapter 13), although that fresh eggs or miracidia are reaching the ponds, an some data suggest that salmonellae may survive for 2 event that can be prevented by using only sewage months in fish guts (see chapter 15). treated in stabilization ponds or stored night soil (see There is little information about the carriage of chapter 32). nonbacterial pathogens by fish. One must assume that viruses, protozoal cysts, and helminth eggs can all be PATHOGEN CONTROL. In summary, fish farming carried, and even concentrated, in or on fish and that uses excreta or sewage carries with it the hazards thereby infect the eaters or handlers of fish. Helminth of passive carriage of a range of pathogens and of eggs will tend to settle to the pond bottom and therefore transmission of Clonorchis and schistosomes in some may only be ingested by bottom-feeding fish (such as parts of the world. Pathogen control may be the common carp, Cvprinus carpio). accomplished by: HELMINTHS HAVING FISH AS INTERMEDIATE HOSTS. * Enriching ponds only with treated sewage, stored The second, and quite distinct, health problem night soil, or sludge associated with fish farming is the transmission of * Allowing fish to reside in clean water for several worms parasitic to man that have fish as intermediate weeks prior to harvesting hosts. The major helminths of this kind are Clonorchis * Clearing vegetation from pond banks to discourage host. Te mjor elmnth of hiskin are Clnorhis the molluscan intermediate hosts of Clonorchis and sinensis (Chinese liver fluke), Diphyllobothrium latum the scansoso es (fish tapeworm), Heterophyes heterophyes, and Meta- the schistosomcs gonimus yokogawai. Of these, Heterophyes and * Promoting good hygiene in all stages of fish Metagonimus are of no major public health importance handling and processing (they are primarily parasites of dogs and cats, and * Discouraging the consumption of undercooked Heterophyes only infects fish in brackish water-see fish. chapter 30). Diphyllobothrium infects pike, perch, turbot, and other fish found in lakes or rivers and is not Algal culture associated with enriched ponds (see chapter 25). Instead of growing fish in waste-enriched ponds with Clonorchis sinensis and the related species of cat liver large algal populations, it is possible to harvest the flukes, Opisthorchis viverrini and 0. felineus, however, algae directly. This is as yet only an experimental are associated with excreta-fed fishponds and are technique, but it may well find large-scale application intensively transmitted where fish are eaten raw or in the coming decades. The advantage is that partially cooked. Infection occurs principally in China, harvesting at a lower trophic level ensures far higher Korea, Taiwan, Thailand, and Vietnam, and the local yields of biomass and protein. For instance, the yields prevalencecanreach60percent.Cookingoffishmustbe to be hoped for from sewage-enriched fishponds are in thorough to kill the encysted larvae, and most the order of 10,000 kilograms per hectare yearly 106 HEALTH HAZARDS OF EXCRETA (Muthuswamy and others 1978), whereas algae Some are harvested wild, and some are cultivated; they production in high-rate ponds may be up to 150,000 include water spinach (Ipomoea aquatica), water kilograms per hectare yearly. The algae are appro- chestnut (Eleocharis dulcis or E. tuberosa), water ximately 50 percent protein, and thus protein yields of hyacinth (Eichhornia crassipes), water bamboo 75,000 kilograms per hectare yearly are achieved. This (Zigania spp.), water calthrop (Trapa spp.), and lotus compares favorably with protein yields from rice (56 (Nelumbo nucifera). Some of these plants (for instance, kilograms per hectare yearly), corn (270 kilograms per water spinach) are intensively fertilized with human hectare yearly), and soybeans (650 kilograms per and animal wastes, whereas others are grown in water hectare yearly) (McGarry 1971). that may be incidentally contaminated (National Algae may be harvested by flocculation with lime or Academy of Sciences 1976). aluminum sulfate followed by flotation (McGarry Attention has recently focussed upon the use of 1971), or by partial removal by microstraining. Oswald water hyacinth in waste treatment and recycling and others (1978) reported that algae are harvested systems (Dinger 1978a, 1978b; Wolverton and from shallow ponds in the Philippines by simple MacDonald 1979). Water hyacinth removes nutrients, sedimentation, with a production of 47,000 kilograms metals, and phenols from wastewaters (Cornwall and per hectare yearly. These various methods produce an others 1977). The hyacinth can be harvested and used algal paste or sludge containing 8-10 percent solids, as animal feed, processed to produce fertilizer, or used which is then sun dried. An overview of the engineering to generate methane (see the section on biogas below). and economic aspects of algae production in high-rate If water hyacinth is introduced, however, the ecological ponds is given by Lee and others (1980). consequences of its escape into irrigation systems (it grows rapidly and can clog waterways) must also be HEALTH ISSUES. High-rate ponds have a short considered. Such systems for intense recycling of retention time of around 1 day. Pathogen removal is wastes are usually fed by sewage but could be fed by therefore minimal, and the harvested algae will be rich night soil or sludge. in excreted viruses, bacteria, protozoa, and helminth eggs. HEALTH ISSUES. The health hazards associated with these aquacultural practices are of three types. PATHOGEN CONTROL. The most effective removal First, there is the occupational risk to those who process is sun drying. Ifthe algae are dried to less than 5 work in the water, especially where intensive use of percent water, pathogen removal will be complete. If night soil occurs. These workers may accidentally not, pathogens will survive to a degree dependent upon swallow pathogens or carry pathogens back to their drying time, final moisture content achieved, and homes on their clothing or bodies, and they may sunlight intensity. There are no data on pathogen become infected percutaneously with schistosomiasis survival on drying algae, but it may be assumed that in areas where the disease is endemic and the protozoa will be rapidly removed (in a few weeks) and intermediate host snails reside in the ponds or flooded that bacteria may be killed by algal toxins and other fields. factors. Viruses and helminth eggs will be long-term Second, the harvested plants may be heavily survivors, with the latter enduring for a year or more if contaminated with pathogens and may infect those who moisture content in the algal sludge stays above 10 harvest, handle, prepare, or eat them. Some of these percent. plants, such as water chestnut in China, are eaten raw. The health hazards involved in the reuse of this algal Third, the parasitic fluke Fasciolopsis buski is locally product will vary. If the algae are fed to cattle, the important in some parts of Asia and may infect 10 major requirement will be the elimination of Taenia million people. This worm has a life cycle that moves saginata eggs, Salmonella spp., and Mycobacterium from man (or pig or dog) to snail to water plant to tuberculosis (see above). If they are fed to chickens, the man. Animals or people become infected by eating major requirement may be removal of Salmonella and the encysted metacercariae on water plants, especially Campylobacter. If they are fed to people (as in Japan), Eleocharis, Eichhornia, Trapa, and Zigania (see chapter they will require thorough disinfection prior to 28). packaging and marketing. PATHOGEN CONTROL. Control of these health Macrophyte culture problems depends chiefly upon the treatment of night Around the world, but especially in Southeast Asia, soil and other wastes prior to their discharge or prior to many water plants are used for human or animal food. their use as fertilizer for aquatic plants. The health EXCRETA REUSE AND EFFLUENT DISCHARGE 107 requirements for a particular plant production system heated (although they may be lagged or buried), and so must derive from a consideration of exactly what kinds they operate at around ambient temperatures. Gas of process are being used to grow which crops, and the production falls off considerably at lower temperatures degree of mechanization incorporated. In addition to and may be negligible below 15°C. adequate treatment of the fecal wastes used, attention to crop harvesting and marketing techniques and education for both producers and consumers are Pathogen control in reuse of biogas plant slurry important preventive health strategies. The health problems associated with biogas plants come entirely from the reuse of the slurry because the gas production itself has no health implications (that is, Reuse for Biogas Production unless the digesters explode or the gas starts a fire). Average retention times in biogas plants are commonly When organic wastes are digested anaerobically, a short (5-30 days), and the operation is usually mixture of methane, carbon dioxide, and other gases is continuous, rather than batch. Pathogen removal will given off. This gas has become known as "biogas" and therefore be considerably less effective than in can be produced in various quantities by different conventional sludge digestion processes."0 Protozoal technologies. In conventional sewage treatment works, cysts should not survive, but pathogenic viruses, anaerobic sludge digestion produces biogas that is bacteria, and helminth eggs may be expected to be sometimes used to heat the digesters or for some of the present in the effluent slurry in considerable con- other energy needs of the works. Biogas production centrations. usually refers to the production of methane on a small There is little information from the field on the scale by individual farmers, communes, or rural quality of effluent from biogas plants. Data from China institutions in hot climates. (McGarry and Stainforth 1978) indicate an average of 15,000 helminth eggs, 4 hookworm eggs and 8 x 107 E. Technical description coli per liter of biogas-plant effluent. In the same report the authors found that survival times for Salmonella, Biogas digesters have been installed in large Shigella, spirochetes, schistosome eggs, and hookworm numbers in China, and it is probably there that the eggs in the anaerobic environment of the biogas tank technology has become most developed (McGarry and are up to 44 days, 30 hours, 30 hours, 40 days, and 75 Stainforth 1978) (see figure 7-t1). Significant numbers days, respectively. Therefore, for a plant with a also operate in India, Korea, and Taiwan. The biogas retention time of 10-30 days, it can be expected that plants are fed with diluted animal feces, with or without salmonellae, schistosomes, and hookworms will be in human excreta and with or without vegetable refuse. the effluent, but that shigellae or spirochetes will not. The effluent slurry is reused in agriculture9 and can Ascaris eggs will survive considerably longer than also be used to enrich fishponds; the biogas is used hookworm eggs and therefore will also be present. (It is primarily for domestic cooking and lighting. The dung likely that the major proportion of the 15,000 helminth from one medium-size cow or similar animal may eggs per liter reported in the study mentioned above produce around 500 liters of gas daily, and the calorific were Ascaris.) In another investigation in China value of this gas may be around 4-5 kilocalories per (Research Institute of Military Medical Sciences 1977), liter (McGarry 1977). In contrast, human excreta only inflow to a biogas plant contained 5.4 x 106 E. coli per produce 30 liters of biogas per person daily. The liter, whereas the outflow contained 1.4 x 104 (a 99.7 process is very sensitive to temperature. In the percent reduction). Shigellaflexneri, kept in conditions mesophilic range, optimum gas production occurs at simulating those of a biogas tank, survived for up to 13 around 35°C, but in rural applications digesters are not days, thus contradicting the study reported above. It is clear from the data above that the effluent slurry 8. Inadditiontothetwodesignsofbiogasunitsshowninfigure7- from a biogas plant is unlikely to be significantly less 1, the reader will find further details of the technology in Barnett, pathogenic than raw sludge. Its direct reuse on crops is Pyle and Subramanian (1978); Freeman and Pyle (1977); McGarry therefore not advised (see "Reuse in Agriculture," (1977); McGarry and Stainforth (1978); Rybczynski, Polprasert and above). It may, however, be reused in agriculture McGarry (1978); Subramanian (1977); and Van Buren (1979). following prolonged drying (>1 year) or after 9. It is reported from China that biogas slurry increases the yields of corn and wheat by 19 percent and of vegetables by 50-60 percent 10. See the previous chapter, the section "Conventional Sewage (Research Institute of Military Medical Sciences 1977). Treatment" and figures 6-5 and 6-6. 108 HEALTH HAZARDS OF EXCRETA 2.000 1.000 Gas Cylinder made of welded iron sheet Polyvinyl chloride pipe inlet Used sump oil Liquor outlet pipe Digesting Settling waste tank 2 Concrete or brick wAalls ; Concrete slab South Pacific design Slurry Gas draw-off pipe Displaced liquid Connected settlement \ storage area opening area Ground r > - > c ~~~~~~~~~~~~~~~~~~~~~~~~~ ~~level * . :*. 4 *.d A.\44, '*@4. c .o Gas storage area Liquid level v . .. ~~~~~~~~~~~~~~~~~~~~~Slurrv outlet Exceeta inlet .chamber chamber ._ Digesting / Groove for drop board Chinese design Figure 7-1. Tvpiccd bio gas digesters (dimensions in millimeters). From Kalbermatten and others (1982): top, from a design by G. L. Chan EXCRETA REUSE AND EFFLUENT DISCHARGE 109 composting (see chapter 5; the area of land required for chapters 2 and 3). Poor and seasonally arid countries prolonged drying will be so great that composting will are especially at risk from rivcr or lake pollution of this generally be the preferred treatment method). Biogas kind for two reasons. First, the waterside dwellers may plant effluent may also be used to enrich fishponds. have no alternative, potable water supply and therefore Clonorchis sinensis eggs will be eliminated in the plant, may be compelled to use the polluted water. Second, at and the health hazard involved is the passive some period of the year river flow may be low or transmission of other pathogens by harvested fish (see nonexistent, so that the discharged effluent will receive "Reuse in Aquaculture," above). little or no dilution. These factors make it essential to guard against substantial pathogen pollution of lakes and rivers. Discharge of Effluents HELMINTHS WITH AQUATIC INTERMEDIATE HOSTS. This chapter began with an expression of the view The excreted helminths that require one or more that sewage effluent, sludge, and night soil are intermediate aquatic hosts are: Clonorchis sinensis, important natural resources to be reused if possible. Diphyllobothrium latutm1, Fasciola hepatica, Fasciolopsis There will be occasions, however, when the most buski, Gastrodiscoides hominis, Heterophyes heter- economically or environmentally appropriate solution opliyes, Metagonirnus vokogawai, Paragonimnus wester- to disposal is not reuse but the discharge of wastes to mani, and Schistosoma spp.11 rivers, lakes, the sea, or groundwater. The health Fasciola is primarily a parasite of cattle and sheep implications of each of these alternatives are discussed and is present in wet pastures and small streams. in this section. Fasciolopsis and Gastrodiscoides are associated with the cultivation and ingestion of water plants (see Into rivers and lakes "Reuse in Aquaculture," above). Heterophyes and Metagonimnus are of limited public health importance The survival of pathogens in freshwater has been and have a very restricted geographical distribution. It examined in chapter 4. Survival times are considerable is thus Clonorchis, Diphyllobothrium, Paragonimus, and for all groups of organisms, and they increase in the Schistosoma infections that are associated primarily following order: protozoa, bacteria, viruses, and with discharge of effluents to rivers and lakes. helminths. Moreover, pathogens may travel sub- Clonorchis sinensis-and the related helminth stantial distances after being discharged into fresh- species Opisthorchis felineus and 0. viuerrini-are water. Pathogens discharged into rivers and lakes may transmitted from human (or dog or cat or other fish- contaminate fish in the same way described for marine eating mammal) to snail to fish to human, and they are discharge (below). Where discharge is to a river, particularly associated with fish farming in ponds pathogens may be carried to its mouth, where they may enriched with excreta. Diphyllobothrium latumn is infect shellfish. transmitted from human (or dog or bear or other fish- eating mammal) to copepod (minute crustacean) to HEALTH ISSUES. There are two overriding health fish to human. It is especially prevalent in lakeside problems associated with discharge of effluents into areas of temperate countries. Paragonimus westermani rivers or lakes: pathogens may be ingested by is transmitted from human (or many other animals) to waterside human populations who use the river or snail to crab or crayfish to human. These three lakewater for domestic purposes; and discharge to parasites all maybe controlled by preventing untreated freshwater may promote the transmission of those human excreta from reaching bodies of water where the parasitic worms that have aquatic intermediate hosts. intermediate hosts are found and by persuading affected communities not to eat undercooked fish, WATERBORNE PATHOGENS. People who use a crabs, or crayfish. In the case of Clonorchis and polluted river or lake for their drinking water may Paragoniimus, asexual multiplication takes place in the become infected by pathogens that have previously snail, so that one viable miracidium infecting a snail been discharged into their water supplies. Viral, can ultimately infect many fish or crabs and, thus, bacterial, and protozoal pathogens may all be transmitted in this way-although, where these Ii. A full account of the life cycles and distribution of these infections are endemic in the community, the par.asitic worms, and guidance on the treatment processes req uired to magnitude of this waterborne transmission may be remove eggs from sewage, sludge, or night soil, will be found in Part minor compared with other, more direct routes (see Two. 110 HEALTH HAZARDS OF EXCRETA many people. The discharge of the parasite eggs in the their survival in freshwater.'2 Excreted viruses and effluent must accordingly be cut to extremely low levels bacteria are eliminated very much faster in warm if transmission is to be reduced significantly. In all seawater than in cool seawater. Protozoal cysts and cases, animals other than man act as definitive hosts, helminth eggs do not experience any particular lethal and the management of human excreta alone can never effects in seawater, and their survival is similar to that guarantee the cessation of transmission. But keeping in freshwater (table 4-3). They do tend to settle, all untreated human wastes out of rivers and lakes however, and so present little health hazard. should have a dramatic effect on transmission in most endemic areas. SEAFOOD CONTAMINATION. Fish and shellfish in Schistosome worms are transmitted from human to polluted seawater may be contaminated by human snail and directly to humans through the skin. The excreted viruses and bacteria. The spread of patho- discharge of inadeqately treated wastes to rivers and genic pollution for more than a few kilometers from lakes is a major factor in the transmission of these sewage outfalls is not normally reported, and fish important parasites. Adequate treatment of all wastes caught in the open sea are thereforefound to harbor no before discharge should be helpful in the control of the human pathogens. Fish caught in the littoral zone, fecal species (S. mansoni and S. japonicum). Waste however, may well have excreted viruses and bacteria treatment will have less effect on S. haematobium, on their body surfaces and in their intestines, a hazard whose eggs are passed in the urine, because people may examined in the subsection "Fish farming," above. freely urinate near water. Once again, multiplication Excreted viruses and bacteria may survive in fish guts takes place in the snail, so that a great reduction in the for a few weeks and can infect humans who handle or number of viable eggs reaching the water is necessary eat them, and may also infect animals fed on fishmeal, before a marked reduction in transmission can be which may in turn infect humans. However, a more expected. common hazard is the contamination of fish after they are caught, and most fish-associated outbreaks of salmonellosis or typhoid have been linked to this form Into the sea of contamination. A more serious problem than fish contamination is Night soil and raw sludge are often taken out to the the contamination of edible shellfish (Hughes, Merson open sea by boat and dumped; less commonly, these and Gangarosa 1977). Mussels and oysters are grown wastes are dumped from the shore. Dumping of night along coasts and in estuaries where the salt soil or sludge in the open sea should pose no significant concentration is 0.8-3 percent (compared with 3.5 health problems, but dumping from the shore is so percent in the sea). Shellfish therefore live in the marine offensive that it should never be a feature of any well- environment most exposed to pollution from sewage designed disposal system. Only the more usual practice outfalls and from contaminated riverwater. Because of discharging effluents from sewage treatment they filter water to feed, shellfish concentrate excreted facilities into the sea near the shore is discussed below. bacteria and viruses in their tissues. Salmonella spp. (including S. typhi) and enteroviruses have frequently HEALTH ISSUES. The discharge of sewage effluent been isolated from shellfish at concentrations well into coastal waters can create two kinds of health above those of surrounding seawater (see chapters 15 problem: the risk of contaminating fish or shellfish, and 9). Outbreaks of poliomyelitis, hepatitis A, and which may subsequently be eaten, and the risk of diarrheal diseases all have been associated with the contaminating bathing areas and beaches. ingestion of of shellfish originating in polluted water. Shellfish can be decontaminated by placing them in PATHOGEN SURVIVAL. Enteric viruses and bacteria clean water. Chlorinated water that has been discharged into seawater survive for considerably dechlorinated is often used (chlorinated water is shorter periods than they do in freshwater. Coliforms ineffective because it discourages the shellfish from in seawater undergo a 90 percent reduction in 0.6-8 hours compared with 20-100 hours in freshwater. 12. The survival of indicator bacteria, salmonellae, and en- Fecal streptococci may survive a little longer than teroviruses in seawater are reviewed in chapters 13, 15, and 9, coliforms in seawater, and salmonellae longer still. respectively. Rapid bacterial death rates may be due to the injury of bacterial cells by seawater, such that they cannot grow on standard Enteroviruses survive for longer periods in seawater laboratory isolation media, rather than to actual death (Dawe and than excreted bacteria-90 percent reductions in Penrose 1978). These injured bacteria can be resuscitated by special 15-70 hours-but this is stillconsiderably shorter than techniques, but it is not known whether they are still infective. EXCRETA REUSE AND EFFLUENT DISCHARGE l1l pumping and feeding and so will not flush out viruses and nonswimmers at polluted beaches. The recorded or bacteria lodged in their tissues). Studies reviewed in risks of swimming in seawater containing 102t -0I fecal chapters 9,13, and 15 indicate that 2 days in disinfected coliforms per 100 milliliters were an additional attack water may be sufficient to cleanse shellfish of E. coli, but rate of one to two cases of gastrointestinal illness per that several days are required for elimination of 100 people in the 8-10 days following the visit to the enteroviruses and several weeks for elimination of beach. It must be kept in mind, however, that especially salmonellae. Even small numbers of pathogenic in developing countries the infections that may be bacteria remaining in the shellfish tissues may transmitted to swimmers at polluted beaches will subsequently multiply in warm conditions and infect usually be highly endemic in the community at large someone eating inadequately cooked shellfish. (the community producing the wastes that are A related problem is that of acute gastroenteritis polluting the sea), and swimming may constitute a caused by Vibrio parahaemolyticus. V parahaemolyticus negligible additional risk. Set against this is the has been reported as a cause of acute diarrhea in possibility that swimmers from high socioeconomic several countries, and it may be the single most strata (who experience a low risk at home owing to common cause of food poisoning in Japan (Miwatani adequate water supply, sanitation, and hygiene) may and Takeda 1976). The bacterium occurs widely in be exposed to a substantially increased risk of infection nature and is not restricted to the animal intestine. It is when they bathe in seawater polluted by the wastes of a halophile and has frequently been isolated from all socioeconomic strata. The same level of additional seawater, estuarine water, brackish lagoon water, risk may apply to tourists-who are usually either marine sediments, fish, shellfish, crabs, and prawns local residents from upper socioeconomic groups or (Baross, Liston and Morita 1978; De and others 1977; foreign visitors. A perceived risk to tourists, whether it Felsenfeld and Cabirac t977; Franca and others 1980; is real or imaginary, may have serious economic Sirca and others 1979; van den Broek, Mossel and consequences. Eggenkamp 1979; and Vanderzant and Nickelson 1973). Outbreaks of V parahaemolyticus diarrhea in humans have usually been associated with the To groundwater ingestion of inadequately cooked seafood, and the organism may also be a pathogen of marine fish and Effluents and liquid wastes are frequently discharged shellfish. It remains unclear to what degree disease to groundwater. This usually occurs unintentionally- outbreaks are associated with V parahaemolyticus when soakaway effluent or pit latrine seepage deriving from sewage discharges into estuaries and percolates down to reach the water table, for instance. coastal waters, rather than to naturally occurring It can also occur through seepage losses from the base aquatic reservoirs of V parahaemolyticus. In this of waste stabilization ponds or, in arid areas, when connection it is noteworthy that pathogenicity in effluents are discharged into low- or no-flow streams humans is particularly associated with those strains of that are losing flow to the ground. In some countries in V parahaemolyticus which produce a thermostable which groundwater resources are being deliberately hemolysin (the Kanagawa phenomenon). Yet, in conserved or augmented, treated effluents may be studies in the Andaman Islands (Lall and others 1979), recharged to groundwater as a means of indirect Britain (Ayres and Barrow 1978), India (Chatterjee recycling. [See note on page 116.] and others 1978; De and others 1977; Natarajan, Abraham, and Nair 1980), and Togo (Bockemuihl and HEALTH ISSUES. There are two central questions in Triemer 1974), from 89 to 100 percent of en- considering the health implications of waste discharge vironmental isolates were Kanagawa negative. to groundwater: how far do the pathogens move vertically and horizontally from the point of discharge, RECREATIONAL HAZARDS. An active debate con- and for how long are they able to survive? The tinues about the magnitude of the health risk movement of protozoan cysts and helminth eggs can be associated with swimming in fecally polluted seawater expected to be limited because their size will cause and the correct approach to water quality standards them to be retained in soil. It is therefore viral and and legislation (Cabelli 1979; Evison and Tosti 1980; bacterial movement and survival that are of interest, Moore, Perin and Maiden 1979). Recent evidence from and inadequately treated groundwater is a major Egypt and the USA (Cabelli 1979; Cabelli and others cause of outbreaks of diarrhea (both viral and 1979) revealed a small but measurable difference in the bacterial) and hepatitis A in some countries (Craun incidence of gastrointestinal illness between swimmers 1979). 112 HEALTH HAZARDS OF EXCRETA PATHOGEN TRAVEL. Studies on bacterial movement Nitrates from effluents through soil and rock indicate normal maximum travel This study concerns health problems related to distances of up to 30 meters in sand and fine soils and biological agents contained in excreta. It would be up to several hundred meters in gravel or fractured rock inappropriate, however, not to mention one chemical (see chapter 13). Despite their tendency to become pollution problem, the problem of nitrate accumu- adsorbed onto soil particles, viruses may travel lation, which can occur as a result of waste discharge to through soil for longer distances than bacteria (see rivers lakes or groundwater. Nitrates are an end chapter 9). Retention does not necessarily imply rie,ls or oundater. Nate areaend , . ~~~~~product of the oxidation of many nitrogenous inactivation. It must be noted that, when moving compounds. Nitrate levels may be high in lakes and through soils, the great majority of bacteria and viruses are retained in the first meter and that only a groundwater receiving continuing discharge of raw or treated sewage or wastewaters leaching from pit small fraction is able to travel more than 10 meters. latrines, soakaways, or garbage dumps (Berwick 1979; Brooks and Cech 1979: Nicholson 1979; Schalscha PATHOGEN SURVIVAL. Excreted bacteria and viruses and others 1979). Domestic and industrial effluents are likely to survive for longer in groundwater than in may cause high nitrate levels in receiving rivers during surface water (table 4-3) because groundwater is periods of low rainfall when the rivers are providing cooler, not exposed to sunlight, and has less microbial inadequate dilution. High nitrate levels in surface and and biological activity. Bacterial survival in ground- groundwater may also derive from surface runoff water water may be up to 5 months, with most reduction that has picked up organic material and nitrates from taking place in the first few days. Fecal coliforms soil or agricultural fertilizers. survive longer than salmonellae and can multiply in the The reduction of nitrite and nitrate levels in presence of nutrients (for example, when effluent is wastewaters prior to discharge is normally achieved by reaching the groundwater; see chapters 13 and 15). the action of denitrifying bacteria under anaerobic Virus survival may be similar or somewhat longer (see conditions. Such a process may be included as a chapter 9). tertiary treatment stage in a sewage treatment plant (Anderson and Ibrahim 1978), but its expense and PATHOGEN CONTROL. In areas where there are sophistication makes it inappropriate in most circum- many pit latrines, soakawastabilization stances in developing countries. In hot climates, many pit latrines, soakaways, unlined denitrification sometimes occurs in secondary sedim- ponds, or a recharge system, there will always be a risk entation tanks that have become almost anaerobic. of pathogenic viruses and bacteria reaching ground- The consequent release of gas (N2 and N20) seriously water. In pit latrines, soakaways, and ponds the waste-s . oI pinterfae quiklyabecomes cogds the interferes with the settlement process within the tanks. waste-soil interface quickly becomes clogged with solids and thus more effectively retains these microorganisms. The risks to health occur wheni the HEALTH ISSUEs. Nitrate levels of over 100 milligrams contaminated groundwater is used as a source of per liter of NO3 have been associated with clinical drinking water. The pathogen content of polluted methemoglobinemia in bottle-fed infants (Winton, groundwater will, in general, be much lower than that Tardiff and McCabe 1971). The nitrates are reduced to of surface waters in the same area. Where untreated nitrites in the intestine and thence enter the water is being used for domestic purposes, there will bloodstream, where they oxidize hemoglobin to therefore be a lower risk from wells than from nearby methemoglobin. This molecule is unable to transport streams or ponds. Where water is chlorinated, the oxygen; thus if too great a proportion of methemo- bacterial pathogens will be effectively destroyed. globin is created, serious and sometimes fatal anoxia Special vigilance is required wherever dense and cyanosis may ensue. This condition is rare and populations use untreated wellwater as their only apparently restricted to infants (chiefly those under 3 domestic source and wherever there is widespread use months of age). Exposure to excessive nitrite may also of soakaways or pit latrines. If routine water quality cause methemoglobinemia in animals and fish (Raju monitoring demonstrates a significant pollution and Rao 1979). problem from groundwater, it is necessary to supply Methemoglobinemia is particularly associated with piped water of better quality or to change the excreta bottle-fed infants ingesting powdered milk formula disposal method in use. The former solution will in made up with high-nitrate water. However, Shuval and general be less costly and more practicable than the Gruener (1977) studied the liquid intake of 104 infants latter. (1-5 months old) in Israel and showed that "while EXCRETA REUSE AND EFFLUENT DISCHARGE 113 during the cool months 90 percent of the total liquid soil, it may be possible to prevent these occurrences. intake is made up of milk, as much as 50 percent can be Nitrates may, however, come from many other sources, in the form of tap water supplements during the hottest particularly agricultural runoff, and it may be more month." Thus, in hot climates, even young breast-fed practical to provide an affected community with piped infants may be exposed to a considerable intake of water of low nitrate content. There is currently no high-nitrate water. The same study detected raised simple and economic method of removing nitrate from levels of methemoglobin in bottle-fed infants whose drinking water (Adam 1980; Nicolson 1979), and so water supply contained 45-55 milligrams per liter of nitrate reduction is normally achieved by blending NO3 (the usual accepted standard for NO3 in drinking high-nitrate water with waters having lower nitrate water is <45 milligrams per liter of nitrate or 10 concentrations. milligrams per liter of nitrate-nitrogen). Several factors operating in hot climates and developing countries may have the effect of increasing the probability of an infant's developing methemoglo- Literature Cited binemia. These factors include high fluid intakes due to heat; the practice of boiling water of uncertain Adam, J. W. H. (1980). Health aspects of nitrate in drinking- microbiological quality, which increases the nitrate water and possible means of denitrification (literature concentration; and the high incidence of infant review). Water South Africa, 6, 79-84. diarrheal disease, malaria, and anemia, which may all Anderson, G. K. and Ibrahim, A. B. (1978). Treatment of act to compound any methemoglobinemia caused by high-nitrate wastewaters by plastic media anaerobic filters high-nitrate water. In addition, some antimalarial with particular reference to latex processing. Progress in drugs may induce an increased level of methemoglobin Water Technology, 10, 237-253. in the blood. Despite these theoretical dangers, and Ayres, P. A. and Barrow, G. I. (1978). The distribution of despite the fact that some communities in some 7iVibrio parahaemolyticus in British coastal waters: a report despit the fct tha somecommunties i some of a collaborative study 197 5-6. Journall of Hvgiene, 80, developing countries (for instance, Botswana, Senegal, 281 294. and Tanzania) habitually drink wellwater with several Barnett, A.. Pyle, L. and Subramanian, S. K. (1978). Biogas hundred milligrams per liter of nitrate, it remains Technology in the Third Wtorld: A Multidisciplinar vReview. undemonstrated that any significant amount of Publication IDRC-103e. Ottawa: International morbidity or mortality results. Development Research Centre. High nitrate intake (from drinking water or food) Baross, J. A., Liston, J. and Morita, R. Y. (1978). Incidence of has also been implicated in adult stomach cancers in Vibrio parahoeniolyticus bacteriophages and other Vibrio Chile, Colombia, England, Japan and elsewhere bacteriophages in marine samples. AppliedI and (Cuello and others 1976; Drasar and Hill 1974; Environmentul Microbiology, 36, 492-499. Haenszel and others 1976; Hill, Hawksworth and Benarde, M. A. (1973). Land disposal and sewage effluent: Tattersall 1973). It is hypothesized that nitrite appraisal of health effects of pathogenic organisms. Journal of the Americant Water Works Association, 65, (produced by the bacterial reduction of mgested 432-440. nitrate), secondary amines, and bacteria may come Berwick, M. (1979). Nitrate levels in groundwater from the together in the stomach of individuals with gastric Fleuve, Senegal. Progress in Water Technology, 11, achlorhydria (reduced stomach acidity), or in the 117-120. bladder ofindividuals (especially females) with bladder Bockemuhl, J. and Triemer, A. (1974). Ecology and infection, to produce dimethylnitrosamine-a potent epidemiology of Vibrio parahaemolYticus on the coast of carcinogen of the stomach. The health hazards Togo. 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Vibrio paca- treatment and health safeguards. Technical Report Series haemoltyticus: a problem in mariculture'? JouErntal ofl .Vilk no. 517. Geneva: World Health Organization. Ind Food Technology. 36, 135-139. Young, E. E. (1980). Costs of maintaining public health Viraraghavan. T. and Raman. A. (1967). Sewage treatment in standards tor spray irrigation of municipal waste water oxidation pond at T. B. sanitorium, Madras, India. Water systems. Journal of Enrironmental Q .,i. . 9, 354-358. Note added in proof Since this chapter was written a comprehensi- e hydrogeological review of groundw,ater pollution by excrcta andsewage has been published: Lewis. W. J.. Foster. S. S. and Drasar. B. S. (1982). Tlze Risk of Groundwater Pollution hby On-site Sanitrtion .in Developintg Cozintries. Duebendorf, Switzerland: International Reference Centre for Wastes Disposal. 8 The Human Element in Sanitation Systems DURING THE DISCUSSION of the possible health any sanitation intervention, but program designers benefits from improved sanitation (chapter 3) and the should ask themselves which changes are really specific, alternative technologies for excreta disposal practicable and, conversely, how far social, admini- (chapters 5-7), some rather demanding stipulations strative, or political factors should be viewed as about the social conditions under which maximum constraints on policy options. To do this requires that a benefits can be achieved have been made. Several planner have a good "feel" for a society and the way in beneficial effects can only be expected to occur, for which sanitation is handled within it. Two questions instance, if latrines are properly used and maintained. form the basis of the discussion in this chapter: how do Changes in the public's knowledge and practices may social values and understandings associated with be required before some systems are acceptable. Good health or defecation influence sanitation programs, maintenance of both the private and the public and what possibilities are there for controlling excreta components of sanitation systems is vital. That there disposal through the activities of households, com- are many calls for health education or more effective munity groups or urban government? The questions program administration is a clear indication that the are interrelated because understandings and values social prerequisites for effective sanitation are seldom influence institutions, and the consequences of achieved in practice. Yet the diagnosis of social ills has institutional behavior in turn influence individual often taken a simply deductive form: if a sanitation understandings and values. technology fails, the fault must lie with the users. The social, behavioral and institutional aspects of Careful analysis of these social factors may reveal that excreta disposal, and of programs designed to change sometimes the public's response cannot reasonably be excreta disposal practice, are severely neglected areas otherwise. of study. Very few good field studies or thorough A recurrent theme in this study has been that excreta project evaluations have been carried out. The writings disposal systems must be suited to their environmental of Curtis, Goyder, Kochar, and Streefland in Pacey conditions (the climate, endemic diseases, water (1978) are of interest, as are studies on the comfort availability, or civic wealth), many of which are clearly stations in Ibadan, Nigeria (Ademuwagun 1975 and beyond the control of public authorities. It is too often Pasteur 1979). Recent studies undertaken by the assumed, however, that society is within governmental World Bank have yielded insights into behavioral and control and that communities should simply change to institutional aspects of sanitation programs in Latin accommodate a technology that has been introduced. America (Elmendorf 1980) and in Africa (Feachem, The task is considerably more complex. Because of Mara and Iwugo 1980) and have led to a general review their low capital cost, several of the technologies that of current knowledge on these matters (Elmendorf and are appropriate for the urban or rural poor make heavy Buckles 1980). Some valuable work in this field has demands on the users (table 3-2). They may also levy been carried out not only by those investigating social considerable demands on the limited resources of aspects of sanitation programs, but also by those finance and trained manpower of the public bodies that investigating the social aspects of the transmission of have responsibilities for operation and maintenance. particular excreta-related pathogens. For instance, It is reasonable to hope for some social change from Dunn has written on the behavioral aspects of Note: The first draft of this chapter was prepared by Dr. Donald intestinal parasitism (Dunn 1972), Bancroftian and Curtis. Institute of Local Government Studies, University of Malayan filariases (Dunn 1976) and parasitic diseases Birmingham, England. in general (Dunn 1979), and Kochar (1978, 1979) has 117 118 HEALTH HAZARDS OF EXCRETA done outstanding work on hookworm transmission in of common ground-if not in interpretation, then at West Bengal. Other recent works of interest include a least in practice-between science and these other comprehensive literature review of community partici- beliefs. The ancient Israelites, for example, were pation and education (Van Wijk-Sijbesma 1979) and instructed to take a stick with them on their early contributions by Feachem (1980) and Jackson (1979). morning journeys from the camp to the bush, the stick to be used for burying their feces. This is an effective Relevance of Cultural Values and sanitary prescription in the modern sense, but it is clear Attitudes from the context that the instruction had more to do with the ritual cleanliness of warriors before battle than How people react to excreta disposal schemes or with disease transmission as such (Deuteronomy arrangements depends both upon deep-rooted cultural 23:12). values and upon more mundane matters of cost, Mary Douglas, seeking an explanation of the convenience, and comfort. Each of these may affect user universal existence of taboos, suggests that those things preference or acceptance, and each should be explored become taboo which are difficult to classify culturally in every project in which the acceptability of the (Douglas 1966). A corollary to this idea is that most technology is the least bit in doubt.' Resistance to new societies prefer to maintain a clear distinction between latrines, for example, might be due to inadequate door man and animal: man is the thinker, tool user, made in catches (a mundane factor, yet indicative of a the image of divinity, and so on, whereas animals are preference for individual privacy) or perhaps, for instinctive, confined to their creature strengths, and of Muslims, inadvertent and inappropriate orientation of a lower order of existence. But this distinction is the facilities in relation to Mecca (an objection difficult to maintain, particularly in relation to bodily implicating values and conventions; Goyder 1978). functions. Defecation and excreta are taboo because Cultural interpretations of excreta and defecation they reveal to man an aspect of his animal existence underlie people's responses both to the deposition that he would prefer to forget. This anthropological technologies and to removal and reuse processes. observation may have sufficiently widespead relevance Excreta usually have a rather special psychosocial to explain why man seeks privacy to defecate, status. In many societies excreta are only referred to in defecation is confined to the bush, and excreta are, if everyday speech with calculated disrespect for the possible, avoided. values of society. Excrement is a thing apart, despised, Interpretation aside, a number of fairly universal taboo. How deeply this view prevails varies: for some and deeply felt human reactions to the phenomenon of peoples, excrement is simply dirty, but for others it is defecation exist, all of which can be utilized to promote dangerous, a matter for personal defilement or for evil practices conducive to improved hygiene in the uses, to be scrupulously avoided or carefully disposed scientific sense of the word. Privacy, apartness, and dirt of (Curtis 1978). There are in fact many interpretations avoidance are all values that lend themselves to the use of the significance of excreta besides that of modern of modern excreta disposal technologies. Beyond these science, with its concern for the pathogens that excreta there are a range of widely shared values: smell contain. avoidance, household cleansing, sweeping, clothes These culturally relative interpretations are reflected washing, and so on that contribute to a reliable in the principles and practices of personal hygiene common basis for domestic sanitation programs. found around the world. Many hygienic practices have Effective excreta disposal may, of course, require that little to do with pathogen avoidance (for instance, the people come to have some new understandings of the doctoring of a house against witchcraft), and many health hazards from excreta and of the measures that substances that are of little interest to modern science can be taken to avoid these hazards. There will be some (such as fingernails or hair clippings) may be regarded situations in which traditional understanding and as dangerous. Yet in most cases there is a large element practice-for example, defecating into rivers that are 1. The study of community reaction to a proposed sanitation also water supplies-is strongly contraindicated by project, and the elicitation of support and acceptance, are valuable modern interpretations of health and disease. In these activities in all countries. Krauss (1979) described the replacement of instances, authorities may have to assume didactic a malfunctioning tertiary sewage treatment plant in Greenville, roles, but they can nearly always do so by building Maine, USA, by an innovative land application system after upon traditional culture rather than by starting from extensive public consultation and participation. An immediate scratch. practical outcome was an increased willingness to pay sewer rates on the part of households connected, and an increased demand for The widely shared cultural evaluations of excreta connections on the part of those households unconnected. have an equally common but regrettable side effect: THE HUMAN ELEMENT IN SANITATION 119 people who, by their occupation, come into regular appreciating the position of the user and looking at contact with excreta become themselves persons to be innovations from the user's point of view. For the user, avoided. In many towns throughout the world, the toilet itself is a most important element in the sweepers and night soil removers are drawn from excreta disposal system. He may have to decide disadvantaged minority groups living in segregated whether to invest in one, and he has daily to face using communities within the towns, and their occupation it. Even the most hygiene-conscious people will take tends only further to reinforce their segregation. This is more than cleanliness into account in making these a rather intractable problem wherever some kind of decisions, and disadvantages may not have to be great cartage system is necessary for night soil removal. before some people will opt out of whatever innovation is being proposed. Influence of Social Structure and Organization Cost The most obvious and perhaps most cogent of all Any excreta disposal system IS a complex social soilcntatsnsnttonsthcstfltre. activity involving planners, administrators, politicians, The existing on of sntr faltie(bt and corporation workers as well as the individual user. aThe existing dastributon of sanitary facilities (both Officials, for their part, can plan improved systems but tardothelrichdoiatlargeiexentybecauseaanitationei may face difficulties in raising the necessary resources, e ni. yo the altenatie techno is cooperating with other agencies, delivering the goods, discussed. int bo are heate sech and, crucially, building up routine services for maintenance. There are additional problems in cheaper) in capital terms than the sewerage systems of securing political support for low-income schemes the industrial West, but most of the savings occur in the cost to the public authority that is spared the expense of when upper-income groups, who can better afford to sees2Thcotftetilstemlvsaytllb pay and have more political weight, themselves clamor siderale ast omthe tolets themselves may still be for hiher sandard of srvice considerable, and at some point down the scale of for higher standards of service. Politicians face the full brunt of deciding priorities in poverty it ceases to be reasonable to expect people to urban development and, if they have to recruit public pay for their own installations. In many urban support to keep themselves in office, they often face environments sanitation programs must be seen as pressures to employ more sweepers or to favor attempts to overcome one of the multifarious effects of particular parts of the community. Workers, such as poverty; as such, they are bound to involve a degree of the operatives of cartage systems, will also have a government intervention through subsidies. Where excreta have an economic value, some of the disposal number of preoccupations besides service to the city. cotcabealndagisthexcednom They must secure for themselves a living wage and costs canre b talanced agaim st the expected income tolerable working conditions, and in their struggles with the authorities or with a public unwilling to see cartage than the in-house costs of toilet fitments. taxes increased they will use what sanctions they have at their disposal, chiefly the disruption of services. Convenience In short, whatever high ideals about the quality of The location of latrines is important and must human life may be embodied in sanitation programs, balance advantages. Sometimes a technology con- such programs cannot escape being a part of the strains the choice of location, but, assuming that all complex social system of a city, and any attempt to options are open, toilets may be sited inside the house make them work better has to take this complex system or compound or some distance away. People may be into account. The following sections exanmine these sensitive about such matters as the prominence of the social values and organizational issues in relation to toilet to public view, and such factors must be the deposition, transport, and reuse of excreta. evaluated in detail for each situation. Some general principles, however, may be postulated. Social and Behavioral Aspects of Latrine If the latrine is sited at some distance from the living Design quarters, people may be discouraged from using it on 2. See Kalbermatten, Julius and Gunnerson (1982) for an economic comparison of alternative sanitation technologies and for technical innovations because many factors enter into proposed "sanitation sequences" that enable users to improve their their choice. But much can be gained by the planner's sanitation facilities to a level and at a pace they can afford. 120 HEALTH HAZARDS OF EXCRETA dark nights or in inclement weather. Yet if it is close to are difficult to predict. There are the well-recognized the house, there may be a feeling that defecation is not cultural preferences for sitting or squatting (the latter adequately segregated from the rest of daily living. In a in part an act of avoidance of physical contact with new tenement project in Madras where toilets were possibly defiling surfaces), and there are also strong provided in each flat, housing officials found that some commitments to particular anal cleansing procedures of these were filled with sand and the space used for that must either be accommodated by the new other purposes. One explanation of this response is technology or, if necessary, changed. Additional design that defecation within these small apartments, even considerations are that children have anxieties about behind closed doors, was unacceptable to the cavernous holes in squatting plates, that the aged may occupants (Curtis 1978). have special needs (the surroundings must not be Sufficiently private locations for outside toilets may slippery, for example), and that hot and malodorous be difficult to find in urban environments. Draft plans latrines discourage all users. for an urban site and service scheme in Africa made A vital aid to comfort has been the inclusion of provision for the siting of latrines in the front corner of personal washing facilities in toilet installations, as in plots, where they could be conveniently linked to sewer the comfort station program in Ibadan, Nigeria lines along the roads. But there were considerable (Ademuwagun 1975; Pasteur 1979). Facilities for hand doubts as to whether this technical convenience would washing at the place of defecation are highly desirable be socially acceptable-the first thing to confront in any case, but total body washing in privacy could household visitors would be the toilet. A privy should also be much appreciated. In India, for example, be private. Most societies have conventions relating to customary sanitary prescriptions require a bath to domestic space-for example, that the back of the follow defecation (Kochar 1978); in these circum- house is private, the front public and these stances, linked bathing and toilet facilities would conventions need to be discovered and respected. greatly encourage use of both private and public People may be sensitive not only about the location latrines. Comfort concerns both physical conditions of the toilet but about the journey to it as well. In and the fulfillment of conventional expectations. Botswana it was found, through careful monitoring of Householders in B6tswana found the ventilation gap a latrine program, that the act of carrying a container left at the bottom of doors to their outside toilets of water to the new privy (something quite acceptable disconcerting because people could see their feet. in India) was an embarrassing announcement to the Conventional expectations may be numerous, and the world at large of an individual's intentions. The design only way to discover them is by carefully monitoring was subsequently modified to provide a water source at reactions to new designs in each situation. the latrine. In many rural areas latrine programs may face the A major difficulty with toilets may be providing problem that people find the bush more acceptable and access to the right people at the right time. more comfortable than pit latrines or even some more Householders may be inclined to keep outdoor latrines sophisticated teclnologies. This choice may reflect locked to prevent misuse by passers by, with the both that defecation is often regarded as a shameful unfortunate consequence that they are then not activity properly confined to the wilds [as Muhondwa available for children to use during the day. Similarly, (1976) found in Tanzania] and that the latrines may be in the tenement project in Madras, interior toilets were hot, malodorous, and fly ridden (an acknowledged inaccessible to children while both parents were out tendency of many pit latrines). The first problem seeking work during the day (Curtis 1978). Private decreases when the bush becomes inaccessible, as in toilets have to be carefully designed and located to town, or is so diminished that it constitutes highly secure both adequate access and adequate control. contaminated spinneys or copses in areas of intensive Counterbalancing these factors is the fact that most cultivation. At this point the population presumably toilets provide a degree of privacy such that the time of becomes susceptible to new interpretations of what day when defecation may conveniently take place is constitutes an appropriate environment for defecation. greatly extended from the dawn or dusk periods that Latrines can be presented as answers to the problem of are often favored by those with no facilities at all. privacy, and an analogy with the bush may be maintained by siting the facility at a suitable distance Comfort from the house. Crowded urban environments present opportunities for creating new conventions, practices, Comfort has been found to be a great selling point and concepts of comfort that program directors should for latrine programs, but again the social requirements seize upon. THE HUMAN ELEMENT IN SANITATION 121 Group or communal toilets and pays him from a communal fund or allocates Private, domestic latrines have so many advantages responsibility for cleaning and maintaining the to the user over any arrangements by which members separate toilets to each of the participating households. to te usr oer ay arangment by hlc memers The pilot scheme was monitored by a health education of different households share their facility that they are te who ideme seved blems educatin alwys refrabe wereerpeole an ffod tem nd team who identified several problems (Ademuwagun always preferable wherever people can afford them and 1975). Cleaners were often badly in arrears in their pay, space is available. High costs and problems of land an hr h ol hmsle neto ocr scarcity, however, may oblige authorities to select ' w p y communal facilities even though, from past experience, out cleaning and maintenance, the constant attention commnallaclltes een houn, rom asteXprleceX of the health education team seemed to be necessary if their success is highly problematical. The difficulty in tandards ere to be u A ceproble all cases is maintenance. Public toilets have a poor appeared to be paying for water and electricity, and in record in this respect and have inherent shortcomings. some cases supplies were withdrawn. This last problem It takes only one misuser, perhaps a child avoiding the . . frightening squatting hole, to establish a chain of rie quesio about h s d t ask betwee subsequent mius fo whc nooei .iln otk the public authority and the local groups. Voluntary r qesonsbii. . . groups often have difficulties in collecting money from responsibility. their members on a routine basis (Feachem and others There are two possible responses to the problem of 1978) because defaulters encourage those who would neglect of public facilities that public authorities can otherwise be inclined to pay regularly to be similarly make: attendance by a cleaner, or the provision of lax public toilets for identified or self-identified groups of In most cases public facilities must be provided households. The first is an expensive proposition either by public authorities or by these authorities in requiring the deployment of cleaning personnel on a conjunction with the users. Where night soil has a large scale. In general, arrangements of this sort are commercial value, however, there may be potential for common only in public places such as market areas or the commercial organization responsible for reuse to main thoroughfares, where provision must be made for provide the toilets themselves. In Indonesia fishpond large numbers of occasional users who are passers by. owners, who stand to make a profit from the The additional expense of an attendant is often covered cultivation of fish, provide a number of latrines by a small charge to the users, which of course is not overhanging their ponds for the use of the neigh- possible in toilets designed to serve the requirements of borhood. Whatever virtues or vices attend this system, a resident population. The arrangement most likely to the great advantage is that management and ensure sustained cleanliness is to have one cleaner . . a A chaper maintenance by a public authority IS minilmized constantly stationed at each public toilet. Abecause the fishpond owner has to maintain the alternative is to have a cleaner responsible for several facilities in a manner that is attractive to the requisite public toilets, which he continually travels among. This potential users. It is not clear, however, whether in latter option can work well if the cleaner has adequate other circumstances cartage systems, for instance water supply and equipment, so that he can cope with a it is possible to push contractors beyond servicing into toilet that has become grossly fouled since his last visit. providing the latrines. This system is used to maintain public toilets in Beijing, China: the cleaner has a three-wheeled bicycle, with equipment and boxes, and water is available at each Social and Organizational Aspects of facility (Feachem, personal observation). The potential for achieving better management of E C public toilets by associating them with an identifiable group of households is currently being explored in the It is perhaps regrettable that a sewerage system is not Ibadan comfort station program in Nigeria where, in only a technically efficient removal system (given the the old town, the indigenous social structure of family massive financial outlays to introduce it) but, once groups provides a framework for the social control of constructed, that it is also the easiest to organize and latrines (Pasteur 1979). The facilities, designed to serve run. The technology may in part be complex, but the between 350 and 700 people, are built by the need for servicing is limited. Instead of an army of authorities with the people themselves providing the sweepers required to empty buckets and pushcarts, a land from family holdings and contributing to the cost sewerage system may be run by white-coated of construction. The group, under the leadership of the technicians assisted by a few manual workers whose traditional family head, then either appoints a cleaner job is performed away from the public gaze, 122 HEALTH HAZARDS OF EXCRETA either underground or beyond the urban bounds. The regarded occupation, and that is being of low social labor force required is small, elite, and dispensable for status without any occupation at all. Thus, from a short periods. Breakdowns in a sewage system usually social as well as economic point of view, whether night cause environmental pollution at the treatment works soil cartage systems are appropriate or not depends on and beyond rather than any direct contamination or the state of the wider economy. If there are equally well- disruption of the domestic environment of the users. In paid or better jobs available, then it must be assumed other words, as is the case with many modern that night soil removers will select these, and there will technologies (Dickson 1974), a sewerage system is more be a strong argument for changing the disposal system. amenable to social control than any of the less If there are not otherjobs available, there will be strong automated technical alternatives. pressure from the disadvantaged groups themselves to By contrast, cartage in its simplest bucket-latrine maintain the cartage systems. form requires large numbers of workers carrying out If hand-operated cartage systems remain necessary, routine collection of night soil from households by something can be done to improve the social position using buckets, boxes, or barrows that must be emptied of the operator by improving the terms and conditions into carts of some sort for conveyance to a disposal of service. Low status frequently is reinforced by low point. The buckets have limited capacity, and the pay, which, if improved, would somewhat counteract system is prone to crises both from mismanagement low status. It may be difficult, however, to alter the pay and from collective action on the part of the workers. structure radically while there remains a reserve corps Civic authorities face on the one side citizens with of unemployed sweepers without simply encouraging various means at their disposal for insisting upon subcontracting. Government policy on public sector reasonable service; on the other, authorities face pay may also limit the options and create problems of workers who wish to exercise what strength they have its own. In some cases minimum wage legislation may to get a reasonable reward for performing an set the scale for manual labor in the public sector above unpleasant and socially degrading job. Which party market rates, causing labor-intensive technologies to gets the relative advantage depends upon the labor be uneconomic while there are still surplus workers market, politicians' need for political support, and willing to do the job. In other cases, as in Port Sudan, other factors; in any case, cartage systems often present Sudan (Spencer 1978), rates of pay set at levels not organizational and political problems for civic competitive with private sector employment make it authorities. If these authorities decide to change to difficult to build up and train adequate staff. But even if sewerage systems, the decision may reflect a desire to it is difficult to make major changes in pay, working escape from the organizational problems involved in conditions can be improved in other ways. Where work cartage. clothes are issued, they often are similar in appearance Direct handling of night soil in cartage systems leads to those of convicts and serve to set the users socially to a situation in which it is often only groups of apart more than to protect their bodies. Equipment is strangers, refugees, or other disadvantaged minorities also often poorly designed and badly maintained, and of the urban community who are prepared to take the facilities for washing and changing after work are job. In the Indian subcontinent the work is associated inadequate or neglected altogether. Improvement in with the sweeper castes, whose untouchable status the any of these dimensions will improve the social status Indian government has been endeavoring to overcome. of night soil removers. In practice this kind of social change has proved very Operators of vacuum trucks have a stronger difficult wherever there is continuing association of a bargaining position than workers in manual cartage caste or single group with occupations such as night systems because they are more skilled and, in any soil removal, and eliminating a stigmatized occupation one town, fewer in number. Sealed vaults, because they is a major additional incentive to changing an excreta have no treatment potential and limited capacity, also disposal system. But even stigmatized occupations have a crisis point if they are not emptied on time, and may be in strong demand if alternative sources of organized labor can use this to its advantage. Septic employment are unavailable. Operators in parts of tanks, in contrast, are less crisis prone and may for this cities covered by private cartage systems may have to reason be favored by authorities worried about the purchase the rights to service a street (Streefland 1978), power of their organized labor force to make demands. and municipalities are often under strong political Improved technologies, requiring less direct handl- pressure to expand the number of sweepers in their ing of feces, may facilitate an upgrading of the status of employ. For a sweeper there is perhaps only one thing night soil removers. Jobs with more skill will attract worse than being of low social status in a lowly higher pay, enabling the workers to maintain a higher THE HUMAN ELEMENT IN SANITATION 123 standard of living. One seemingly counterproductive conclusion brings experts into line with the large part effect herc is that, if the social stigma attached to night of mankind that has always favored reuse. In many soil removal is effectively lifted by improved tech- parts of the world the problem is not reuse but how to nology, these jobs may then be open and attractive to persuade people that additional stages of treatment are people outside the minority traditionally filling the sufficiently important for their health to warrant the occupation, so that this minority group loses its increased time and expense that treatment requires. employment monopoly while keeping its low social Elsewhere, however, the idea of reuse is not easily status. accepted culturally. Many people share the prejudice Because many towns will require improved cartage of the villagers in Zola's novel La Terre against the old systems of one kind or another in the future, it is lady who nurtured beautiful vegetables by night soil, important to discover whether the social stigma thus relieving her poverty but placing herself beyond attached to night soil removal can under any the bounds of social acceptance. However deep seated circumstances be removed. Evidence is hard to come these prejudices may be, the situation is far from by. Some reports from China (Streefland 1978) indicate irredeemable. There are several reasons why the that, because of the importance attached to health in significance of cultural barriers to reuse is less than it that society, the status of night soil removers has might first appear. Processing can transform some- improved since the revolution. In a society where reuse thing that is socially unacceptable into something that of excreta has always been practiced, however, it is is much more easily accepted. An analogy may be unlikely that the job has ever carried the stigma that it drawn to the universal practice of food preparation: an does, say, in India, where the rituals of excreta animal or vegetable, unattractive in the wild state, avoidance are highly developed. Furthermore, the becomes appetizing when cooked, arranged on a plate, Chinese approach of involving the public in hygiene and served with a sauce; so may excreta, despite their and sanitation improvement committees (Schwartz malodorous nature and value-laden associations, 1977), if tried elsewhere, would not necessarily become attractive when treated and moved to another lead to an improvement in the status of those people environment as compost or fertilizer. Part of the art of who are employed in night soil removal. As with treatment must be the achievement of this cultural attitudes towards excreta and waste disposal, the transformation that would enable farmers to use a willingness of a society to participate in an organized substance with pleasant texture and acceptable odor way in this sector is culturally dependant. This remains for the enrichment of their land. an important area for future investigation. Unlike the true subsistence farmer who experiences In many societies where night soil is valued as a the whole cycle of agriculture from production to fertiLizer, cartage is a private sector activity. Cartage consumption and back to production, a commercial contractors make their money by selling the material farmer produces for a distant and impersonal market to farmers, by being paid for the job of removal itself, or and is better prepared to use any agricultural aids by a combination of both. In some towns, different conducive to a good market return. The urban areas are serviced by small-scale contractors who make consumer, for his part, can only judge food by its agreements with individual householders for night soil appearance in the market stall and knows little of its removal. In others, larger-scale operatives undertake origins. The separation of producer and customer is contracts with city corporations. Some operate simple both geographical and institutional. Its positive aspect cartage systems, others may service septic tanks with is the diminished significance of individual preferences vacuum trucks. Private contractors may be difficult to and prejudices upon the production processes; its control, particularly where they are numerous and negative aspect is that the public must be protected stand to gain from dumping their loads in the nearest from unscrupulous or unhygienic practices through watercourse instead of removing them from the city to bureaucratically administered controls upon these agreed disposal points. A good price for the product, production and marketing processes. Thus, fish grown however, is an effective incentive to efficient night soil in oxidation ponds managed by city corporations removal. under controlled conditions can escape any stigma Social and Organizational Aspects of because, in the marketplace, they cannot be easily identified. In India, for example, produce grown in Excreta Reuse Systems sewage-irrigated fields enters the market unnoticed, It is now widely accepted among agricultural and although in parts of that country reuse of night soil is sanitation planners that reuse of wastes is a desirable not a favored practice. In London, England, on objective if it can be hygienically achieved. This December 23 and 24, housewives of slavonic extraction 124 HEALTH HAZARDS OF EXCRETA (mainly Poles) buy imported carp for their traditional vision of routine operations to the collection of dues Christmas Eve feast, little suspecting that some of these and the control of access to services. Experience past carp have been raised in sewage ponds. and present indicates that this management ability is Finally, at least in the West (and the West as a often the chief limiting factor in sanitation programs great consumer of natural resources is very important (Rybczynski, Polprasert and McGarry 1978). Not only in this respect), prejudices against reuse are being are urban services often inadequate in extent (to be counteracted by a new consciousness of a need to expected in rapidly growing cities), but existing achieve ecologically sound farming practices and systems also suffer from malpractices that add to their patterns of human existence. This takes the form both deficiency. Contractors dump night soil indiscrimi- of an awareness of the undesirability of polluting rivers nately in rivers or drains. Workers gain political and seaboards with untreated or inadequately treated protection when attempts are made to enforce work sewage and of the need to find substitutes for the routines. Members of the public get their houses energy-consuming (often petroleum-derived) artificial preferentially connected to water supplies or sewer fertilizers that are required in large volumes in lines by paying "speed money" to minor officials. The agriculture. This transformation of values, coinciding poor pay their dues while the rich avoid payment. as it does with the more structural changes described These difficulties are unlikely to occur if the public at above, has now proceeded to the point that constraints large is solidly behind the policies of their authorities upon effective reuse are more questions of cost and and can effectively exercise some influence upon the technical feasibility (particularly the problem of mixing course of events. It is noteworthy that in postrevolu- domestic and industrial wastes in most urban sewerage tionary China, where improved sanitation has high systems) than questions of cultural predisposition. If priority, urban public services are backed by voluntary there remain effective scruples regarding reuse, these committees, sponsored by the ruling party, that serve are more likely to lie with policymakers than with the to keep the authorities on their toes, while at the same users themselves, and top managers are the people time mounting health improvement campaigns and most exposed to the new ideologies about conservation other voluntary activities (Streefland 1978). Elsewhere, and the need to manage resources effectively. a major role for community development officials, In summary, how successfully the reuse of urban health education teams, and civic leaders must be the wastes can be controlled depends upon organization. generation of public support for and commitment to On the urban periphery, people may treat and reuse environmental improvement-not so much for the their own night soil in local fields or gardens, making it direct action that this can achieve as for the backing of very difficult for local authorities to establish workable the authorities attempting to carry out their proposals. controls. Similarly, small-scale private contractors in No civic administration can maintain the integrity of night soil removal who service a number of households its programs for long without active public support. and sell their product to farmers in the countryside Furthermore, because the kinds of sanitation schemes may easily escape bureaucratically administered envisaged here require radical changes in the control measures. If the municipality itself administers distribution and organization of services, radical night soil removal or contracts it to large-scale changes in civic consciousness will also be required. commercial enterprises. however, the authority is then Such changes are not always forthcoming. In this in a position to enforce suitable treatment before the imperfect world, realistic plans may need to accommo- product is made available for reuse. date existing interests and commitments and endeavor to promote change in spite of weaknesses in urban government and administration. Two different re- Improving the Management of Urban sponses are currently in evidence. The first is to create Sanitation Systems special-purpose agencies beyond the influence of local interest groups to take responsibility for the develop- The success of sanitation programs hinges largely on ment of a single city (as in the case of the urban the capability of the municipal governments or other development authorities found in most Indian cities), public authorities who must promote, control, and to look after the interests of a particular class of citizen, service the schemes. These authorities must not only or to provide for one kind of service on a regional basis. understand the nature of the task but must also be able There is a trend toward specialized water and to exercise their authority to enforce routines and sanitation authorities in many different parts of the ensure that the public plays its part. The need for world. The protagonists of these special-purpose administrative discipline extends beyond the super- agencies believe that such agencies will be more THE HUMAN ELEMENT IN SANITATION 125 effective development bodies than the traditional civic because some health benefits depend upon authorities because they are free to draw up rational complete coverage of the population, incomplete plans and follow priorities. Yet these bodies often find coverage will frustrate the objectives of the themselves in a competitive position with other program. authorities with similar or overlapping responsibilities, * There is no guarantee that those people who are and they still require constant political support to be most in need will be those who are most willing to effective. participate. To encourage self-help, the authorities The other approach is to rely upon technologies that will be obliged to help those who are prepared to require minimal municipal commitment and to ask the help themselves. Thus, self-help initiatives can potential users to construct and maintain latrines curtail the authorities' ability to decide upon through "self help." Pit latrines or on-site composting priorities. toilets require little municipal effort (see table 3-2) * Self-help can become a popular movement, backed beyond grants or technical assistance as inducements, by politicians for whom it provides a following, enforcement of bylaws if this is deemed necessary, and through which government finds itself committed some long-term emptying arrangements. to providing a level of service it lacks the financial Neither of these two approaches can be regarded as a or manpower resources to meet. substitute for getting wholehearted commitment to * Self-help programs have shown themselves to be improved hygiene and sanitation, based upon a broad much more effective at generating capital in the understanding of potential health and welfare benefits, form of "one-shot" projects such as classrooms, from politicians and citizens alike. This chapter clinics, or dams than in main1taininig services once concludes with a discussion of the strengths and they have been established. weaknesses of self-help schemes (which can be more Some of these difficulties can be overcome if than simple substitutes for municipal endeavor) in authorities take a more rigorous approach to the meeting these objectives, and of health education. organization of self-help projects from their inception.3 For instance, they may need to: Effectiveness and Limitations of Self-help * Enact by-laws requiring all households to provide Schemes themselves with latrines * Stipulate what categories of households they are Thllingness poteint iviauof lself rogrms, lies iong the prepared to assist with grants or technical guidance wilinnes o inivduas r gous, ve amngth and only help those who help themselves within poorest elements in society, to perform tasks such as laying pipes, digging pits, or improving their physical these categories environment for themselves. Self-help schemes can take * Ensure that the number of projects undertaken advantage of the spirit of self-reliance sometimes found does not outrun the funds available by persuading in informal or squatter settlements; they may also political leaders of the dangers in overstimulating work well where the ruling political party is active in demand and by requiring local groups to register urban management and can organize and control their intentions with the authorities before development, as in recent sites-and-services projects in undertaking a project Lusaka, Zambia. Carefully planned self-help exercises * Limit the scope of a scheme to a size that can be Luaa Zaba.aeul lne efhl xrie adequately serviced by the authority in the future. can totally transform a town, as in the case of Port Sudan, Sudan, where unplanned settlements have been In summary, self-help can best be used for clearly rebuilt and provided with basic services through the defined and limited operations, such as urban authorities and the people working in unison for a few cleanliness campaigns or the initial construction of days in each quarter of the town. Critical evaluations of public or private facilities, in which the people's self-help schemes (Chambers 1974; Feachem and contribution reduces costs and generates enthusiasm. others 1978; Holmquist 1970; Lamb 1971; Schaffer It can also be conveniently linked with the broader task 1969) reveal, however, that self-help often gets out of of health education. hand and ends in frustration for all parties. The potential hazards of self-help schemes in sanitation can be summarized as follows: 3. The advantages and dangers of self-help strategies in rural water supply programs, which have many similarities with sanitation * If participation is voluntary, some households will programs, are discussed in detail by Cairncross and others (1980). not participate for one reason or another and, The case against self-help is set out by Feachem (1980). 126 HEALTH HAZARDS OF EXCRETA Appropriate Health Education Curtis, D. (1978). Values of latrine users and administrators. In Sanitation in Developing Countries. Compiled by Oxfam At the beginning of this chapter it was said that some and The Ross Institute of Tropical Hygiene; ed. Pacey, A., values, attitudes, and understandings can be pp. 170-175. Chichester: John Wiley. accommodated by sanitary engineers, whereas other Dickson, D. (1974). Alterniative Technology and the Politics of social factors must be confronted and changed. In rural Technical ( i , London: Fontana/Collins. areas little progress can be made in cholera elimination Douglas, M. (1966). Purity and Danger. London: Routledge while people continue to locate privies over rivers that and Kegan Paul. downstream are other people's water supply. Health Dunn, F. L. (1972). Intestinal parasitism in Malayan education campaigns have to address specific issues of aborigines (Orang Asli). Bulletin of tihe Worldt Health this kind while simultaneously creating a general Organtization, 46, 99-113. awareness of the potentials of new technologies for - (1976). Human behavioural factors in the epide- improving living conditions. Health education is, miology and control of Wuchereria and Brugia infections. however,~~ ofe diapitn bot i.ndeig an n H. i, - sthePublic Health Societ'v i I I .,,-- .. 10, 34-44. however, otten disappointig both in deslgn and In (1979). Behavioural aspects of the control ofparasitic results. There is a tendency to lecture the public about diseases. Bulletin oJ tile World Health Organization, 57, good hygiene, or balanced diet, or birth control, 499 512. repeating textbook prescriptions without considering Elmendorf, M. (1980). Seven Case Studies ofRural and Urban how the ideas apply in the listeners' particular Fringe Areas in Latin America. Appropriate Technology circumstances. This tendency to patronize not only for Water Supply and Sanitation, vol. 8. Washington, minimizes the many real strengths in existing D.C.: World Bank, Transportation, Water and Tele- knowledge and practice, it is also ineffectual. It fails to communications Department. explore the users' viewpoint or to reveal the genuine Elmendorf, M. and Buckles, P. (1980). Sociocultural Aspects problems that technical innovations pose for them. of Wciter Supply and Excreta Disposal. Appropriate Health education has to be, above all, a dialogue Technology for Water Supply and Sanitation, vol. 5. between officials and users if full benefits are to be Washington, D.C.: World Bank, Transportation, Water obetwnee ofIcals Sandogouse ifd fullrbenefit Are tood b and Telecommunications Department. Obtained (Isely, Sanwogou and Martin 1979). A good Feachem. R. G. A. (1980). Community participation in example of this two-way communication is the health appropriate water supply and sanitation technologies: the education program that accompanied the Ibadan mythology ofthe Decade. P.......1. . ofthe RoYal Society comfort station pilot scheme (Ademuwagun 1975). of London. B, 209, 15-29. Not only were the positive values of the users explored Feachem, R. G. A., Burns, E., Cairncross, S., Cronin, A., here, but practical problems in implementation and Cross. P., Curtis, D., Khan, M. K., Lamb, D. and Southall, maintenance, such as finding suitable sites and paying H. (1978). Water, Health and Development: An Interdisci- for water, were clarified. Without this kind of detailed plinary Evaluation. London: Tri-Med Books. knowledge of the users' perceptual and organizational Feachem, R., Mara, D. and lwugo, K. (1980). Alternative c' . .Sanitation Techiologies Jor Urhan Areas in Africa. problems, campaigns instituted by the authorities are Appropriate Technology for Water Supply and almost certain to founder in disenchantment and Sanitation, vol. 7. Washington, D.C.: World Bank, disorder. Health education has a critical, sensory role Transportation, Water and Telecommunications in community affairs. It cannot merely be the vocal Department. chords of the sanitation authorities, it must be their Goyder, C. (1978) Voluntary and government sanitation eyes and ears as well. programmes. In Sanitation in Developing Countries. Compiled by Oxfam and The Ross Institute of Tropical Hygiene; ed. Pacey, A., pp. 162-170. Chichester: John Wiley. Literature Cited Holmquist, F. (1970). Implementing rural development projects. In Development Administration: The Kenyan Ademuwagun, Z. A. (1975). The Ibadan Comfort Stations: An Experience, eds. Hyden, G., Jackson, R. and Okumu, J., pp. Experiment in Environmental Sanitation Health Education. 201 229. Nairobi: Oxford University Press. Ibadan: African Regional Health Education Centre, Isely, R. B., Sanwogou, L. L. and Martin, J. F. (1979). Faculty of Medicine, University of Ibadan. Community organization as an approach to health Cairncross, S., Carruthers, I., Curtis, D., Feachem, R., education in rural Africa. International Journal of Health Bradley, D. and Baldwin, G. (1980). Evaluationfor Village Education, 22 (supplement), 1-19. Water Supply Planning. Chichester: John Wiley. Jackson,T. (1979). Rural sanitation technology:lessonsfrom Chambers, R. (1974). Managing Rural Development: Ideas participating research. .4ssignment Children, 45/46, 51-74. and Experiencefrom East .4frica. Uppsala: The Scandina- Kalbermatten, J. M., Julius, D. S. and Gunnerson, C. G. vian Institute of African Studies. (1982). Appropriate Sanitation Alternatives: A Technical THE HUMAN ELEMENT IN SANITATION 127 and Economic Appraisal. World Bank Studies in Water Low-Cost Technology Options for Sanitation: A State-of- Supply and Sanitation 1. Baltimore, Md.: Johns Hopkins the-Art Review and Annotated Bibliography. Publication University Press. IDRC-102e. Ottawa: International Development Kochar, V. (1978). Culture and hygiene in rural West Bengal. Research Centre. In Sanitation in Developing Countries. Compiled by Oxfam Schaffer, B. B. (1969). The deadlock in development and The Ross Institute of Tropical Hygiene; ed. Pacey, A., administration. In Politics and Change in Developing pp. 176-185. Chichester: John Wiley. Countries, ed. Leys, C., pp. 177-211. Cambridge: (1979). Culture Parasite Relationship: Socio- Cambridge University Press. behavioural Regulation of Hookworm Transmission in a Schwartz, D. (1977). The mass line as consumer participation West Bengal Region. Studies in Medical Social Science no. and community involvement: a comparison between the 1. Varanasi, India: Centre for Medical Social Science and Chinese approach and "Western" health education Social Medicine, Banaras Hindu University. principles. International Journal of Health Education, 20 Krauss, A. P. (1979). Design involvement leads to public (supplement), 1-17. acceptance. Water and Wastes Engineering, 16, 50-52. Spencer, K. (1978). Managing the expansion of Port Sudan. Lamb, G. B. (1971). Peasant Politics. London: Julian Paper presented to the Red Sea Hills Development Friedmann. Conference, 1978. Birmingham: Institute of Local Muhondwa, E. P. Y. (1976). Latrine Installation and Use in Government Studies, Birmingham University. Bagamoyo District: A Study of Sociological Factors. M.A. Streefland, P. H. (1978). The social organization of nightsoil thesis. Dar es Salaam: University of Dar es Salaam. collection. In Sanitation in Developing Countries. Compiled Pacey, A., ed. (1978). Sanitation in Developing Countries. by Oxfam and The Ross Institute of Tropical Hygiene; ed. Compiled by Oxfam and The Ross Institute of Tropical Pacey, A., pp. 133-138. Chichester: John Wiley. Hygiene. Chichester: John Wiley. Van Wijk-Sijbesma, C. (1979). Participation and Education in Pasteur, D. (1979). The Ibadan comfort stations programme: Community Water Supply and Sanitation Programmes: A a case study of the community development approach to Literature Review. Technical Paper no. 12. The Hague: environmental health improvement. Journal of Admini- World Health Organization International Reference stration Overseas, 18, 46-58. Centre for Community Water Supply. Rybczynski, W., Polprasert, C. and McGarry, M. G. (1978). Part Two Environmental Biology and Epidemiology of Specific Excreted Pathogens SECTION I Excreted Viruses Chapter 9 Enteroviruses, Poliomyelitis, and Similar Viral Infections 10 Hepatitis A Virus and Infectious Hepatitis 11 Rotavirus and Viral Gastroenteritis 9 Enteroviruses, Poliomyelitis, and Similar Viral Infections OVER 100 DIFFERENT VIRUSES are known to be fecally wide variety of diseases (table 9-1). The polioviruses are excreted by man. New viruses are still being discovered, probably the most important. They were the first and several have yet to be fully characterized. Typically enteroviruses to be fully investigated, and because they they infect the alimentary canal and are shed in very are relatively easy to culture they have been used in large numbers by infected persons (Madeley 1979). most experimental work. Diseases caused by these organisms range from the trivial to the serious or even fatal. The occurrence and Identification medical significance of excreted viruses in the Poliomyelitis is unique in being the major per- environment is the most rapidly changing field of manently crippling disease of infectious origin. It is knowledge reported here. A combination of heightened caused by the infection of the central nervous system by environmental concern (especially in the USA), poliovirus or occasionally another enterovirus. It is improvements in laboratory techniques, and the recent usually recognized by a sudden and unexpected onset discovery of important new human viral pathogens of tiredness and weakness in the limbs. Fortunately, the (especially rotavirus) have caused a marked increase in clinical symptoms of poliomyelitis occur in only a very scientific activity, with several hundred papers yearly small proportion of the persons infected, usually a now being published on aspects of excreted viruses maximum of 2 and often less than 1 percent of the total. (EPA 1978, WHO 1979). mxmmo n fe esta ecn ftettl Table 9-1 presents a classification of some excreted The clinical effects of infection range from the viruses similar to that recently proposed by the World asymptomatic through nonspecific minor illness to Health Organization (WHO 1979). This classification meningitis, paralysis and possibly death. There are two Health undoubtedlyunderganization chang 1r this c ati basic patterns of symptoms. The first is a minor illness will undoubtedly undergo changes over the next few arising a few days after infection, lasting 1-2 days and years as new viral agents are characterized and the characterized by mild fever, listlessness, sore throat and taxonomy is revised. For the purposes of this book, vomiting. The second, developing 3-4 days later but excreted viruses are divided into three groups: often occurring without the first phase, is much more e The enteroviruses (chiefly polioviruses, coxsackie- serious. Symptoms of aseptic meningitis, fever, severe viruses and echoviruses), described in this chapter, headache, and vomiting are followed by stiffness of the which also contains some information on aden- neck and back. In paralytic cases the disease usually ovirus and reovirus, as these are often considered leads to progressive weakness resulting in severe jointly with enteroviruses; (see figure 9-1) paralysis. Death, usually caused by respiratory failure, * The hepatitis A virus described in chapter 10 may occur. * The viruses possibly associated with gastroenteritis The disease is short-lived and most people recover (rotavirus, Norwalk agent, and others) described in fully, but many of the most severely affected are chapter 11. permanently disabled. Mortality among the paralytic cases varies between 4 and 10 percent depending on the Description of Pathogens and Diseases virulence of the virus, the degree of medical care and the age of the patient. Diagnosis in asymptomatic cases The enteroviruses are an acid-stable subgroup of the is dependent on laboratory facilities in which the virus small picornaviruses. They are a large group causing a can be cultured from throat swabs or feces. Serological 133 134 ENVIRONMENTAL BIOLOGY & EPIDEMIOLOGY: VIRUSES Table 9-1. Human Excreted Viruses Chapter Number in which Size and of described Virus group Family composition types Diseases or symptoms caused 9 Enterovirus Picornaviridae About 20-30 nanometers diameter. Single- Poliovirus stranded RNA in a 3 Poliomyelitis, meningitis, fever protein shell Coxsackievirus 24 Herpangina, respiratory disease, meningitis, A fever Coxsackievirus 6 Myocarditis, congenital heart anomalies, B meningitis, respiratory disease, pleurodynia, rash, fever Echovirus 34 Meningitis, respiratory disease, rash, diarrhea, fever New 4 Meningitis, encephalitis, respiratory disease, enteroviruses acute hemorrhagic conjunctivitis, fever Adenovirus Adenoviridae About 70-80 nanometers > 30 Respiratory disease, eye infections diameter. Double- stranded DNA in a protein shell Reovirus Reoviridae About 75 nanometers 3 Not clearly established diameter. Double- stranded RNA in a double protein shell 10 Hepatitis A ? About 24-29 nanometers I Infectious hepatitis virus Picornaviridae diameter. Single- stranded RNA 11 Rotavirus Reoviridae About 70 nanometers ? Vomiting and diarrhea diameter. Double- stranded RNA in a double protein shell Astrovirus ? About 28 nanometers ? ? diameter Calicivirus ? About 35-40 nanometers ? Vomiting and diarrhea diameter. Single- stranded RNA in a protein shell Coronavirus Coronaviridae Between 20 and 220 ? Common cold nanometers diameter. Pleomorphic with petal-shaped projec- tions 20 nanometers long. Single-stranded RNA in protein shell and lipid envelope Norwalk agent ? About 20-35 nanometers ? Vomiting and diarrhea and other diameter small round viruses Not Adeno- Parvoviridae About 19 nanometers 4 Not clearly established but associated with described associated diameter. Single- respiratory disease in children virus stranded DNA in protein shell ENTEROVIRUSES, POLIOMYELITIS. AND SIMILAR INFECTIONS 135 tests can also be used. Treatment is supportive in infection for the other enteroviruses. A number have nature. been isolated from pets and other animals associated The other enteroviruses can cause a wide variety of with man, but it is unclear whether or not they were symptoms (table 9-1). These viruses are generally less naturally infected. Reovirus appears to be an dangerous than poliovirus and like poliovirus they exception, having been isolated from a surprisingly only cause significant disease in a small proportion of large range of animal species. Even so, animals have cases. They normally infect the alimentary canal or the not been shown to be a significant source of infection respiratory tract, giving rise to gastroenteritis or for man. influenza-like symptoms. More severe disease is often associated with the spread of the virus to other organs such as the liver or central nervous system. As with .s . polio, the effects are generally short-lived, and Transmission treatment is supportive. Infected persons can shed very large numbers of Diagnosis is either based on symptoms or on virus particles-more than 106 per gram of feces. laboratory culture and identification. Diagnosis is Viruses are also present in throat secretions, especially complicated by the fact that the same virus may cause during the early stages of infection. These particles are different symptoms in different patients and that highly infectious and can remain viable for a different viruses may give rise to similar symptows. considerable period under suitable conditions. Infection takes place when the virus is ingested, possibly in food or water. The primary sites of infection Occurrence are the throat and the lower alimentary canal. Within a few days the virus spreads to the lymphatic system and Thesen. infetionsocatedcurwor tide handve very the blood stream. This phase corresponds with the common. Some Isolated communities have been mnrsmtm fifcin ntesalpooto known that were not infected with poliovirus but few or mosor symptoms of vfectionf In the small propouti none now remain. The other enteroviruses have a of severe cases the virus mfects the central nervous similar distribution, but there are local variations in system, possibly by spread along nerve fibers. both'virustypesan in the virulence of varios . On infecting a suitable cell, the virus diverts the cell's b metabolic activity to the production of large numbers of virus particles identical to the original virus. These are liberated when the cell breaks down, and they either Infectious agents infect other cells or, in the case of the cells lining the Poliovirus is a small spherical particle 28 nano- alimentary canal, are passed out in the feces. meters in diameter and is therefore not visible by Transmission is mainly directly from person to person normal light microscopy (figure 9-1). It occurs in three either by the oral-oral route or the fecal-oral route. serotypes, numbered 1 to 3. A most important There is some indication that in unhygienic conditions characteristic is the degree of neurovirulence, which is the latter route is the most common, with the former known to vary from strain to strain in all three types. route being more important under more sanitary The infective dose is small: probably as little as one conditions. Children under the age of 2 years are the virus particle. Poliomyelitis can occasionally be caused most potent disseminators by both routes. by coxsackie- and echoviruses. There are indications that poliovirus is carried Like poliovirus, the other enteroviruses are sub- between family groups by young children who are both microscopic spherical particles with sizes ranging susceptible and mobile (2-6 year age group). Infection between 20 and 30 nanometers in diameter. The then spreads within the family downwards to number of types in each group is given in table 9-1. nonmobile children and upwards to older children and adults. Up to 50 percent of persons having resistance from earlier infections may become reinfected, but in Reservoir these cases the excretion of viruses is much reduced and symptoms absent. The reservoir of poliovirus is man. Chimpanzees The other enteroviruses are probably transmitted by have been known to catch the disease in captivity, and the same route as poliovirus, whereas the adenoviruses, monkeys may also act as natural hosts, but nonhuman which are normally associated with upper respiratory reservoirs have not been shown to be significant. tract infections, are mainly spread by an airbornc route As with poliovirus, man is the main reservoir of from contaminated throat secretions. 136 ENVIRONMENTAL BIOLOGY & EPIDEMIOLOGY: VIRUSES Figure 9-1. Polio-, adeno-, and reoriiruses under electronmicroscopy. (a) Polioviruses under scanning electronmicroscopy. Other enteroviruses have a similar appearance. Scale bar = 0.1 micrometers. (Photo: World Health Organization, Geneva, Switzerland.) (b) Adenoviruses under transmission electronmicroscopy. Scale bar = 0.1 micrometers. (Photo: A. J. Zuckerman, London School of Hygiene and Tropical Medicine, London, U.K.) (c) Reoviruses under transmission electronmicroscopy. Scale bar = 0.1 micrometers. (Photo: A. J. Zuckerman, London School of Hygiene and Tropical Medicine, London, U.K.) Incubation period Period of communicability Minor illness when present occurs within 2-3 days of Viruses have been found in the throat secretions and infection. Nervous system involvement possibly lead- feces within 24 hours of infection, and contact cases ing to paralytic poliomyelitis may occur between 5 and have been observed within 3 days. Virus excretion, 35 days after infection-on average 17 days. The other mainly in the feces, has been observed for as long as 17 enteroviruses are generally similar to poliovirus. weeks, and on average 7 weeks. ENTEROVIRUSES, POLIOMYELITIS, AND SIMILAR INFECTIONS 137 Most of the other enteroviruses are excreted for a Control Measures shorter period than poliovirus. Coxsackie B viruses, for example, are excreted for I week or less. The In considering the control of enterovirus infections, adenoviruses, however, may persist in a latent form in one must distinguish clearly between reducing the tonsils and adenoids. infection and reducing disease. In the case of poliovirus, for instance, environmental measures may reduce transmission and thus the incidence of infection. Resistatnce However, these measures may increase the incidence of serious clinical disease by deferring the age of first infection to that at which disease is more likely to be Young children are the most susceptible age group, most adults having acquired resistance to poliovirus severe. A survey of 10,000 households in 25 villages in during earlier infections or by vaccination. Infection Gujarat (India) found that the number of paralytic leads to the development of life-long immunty to the poliomyelitis cases per 1,000 households was related to ...i u i mm y s . household income. Among low-income households infecting type of virus, but the individual may still be there were 12 cases per 1,000 houses; among middle- vulnerable to other types. there were 18 cases per 1,000 The severity of the disease is markedly dependent on houses;handeamong high-income householdsrthere the age of the patient; in a nonresistant population, were 24 cases per 1,000 houses (Jhala, Goel and Dave teenagers and young adults show the most severe 1979 2 Contrapevidence isures a recent reve symptoms. Certain other factors have been found to increase the severy of te dshowing that the real (as opposed to reported) annual incsillecthey severity,of theent disculasetionc,uhyn incidence of paralytic poliomyelitis in Burma, Egypt, tonsillectomy, pregnancy, recent noculations physical Ghana and the Philippines is between 233 and 3,800 exertion, and trauma.e Infection by theotherenterovirusesusuallyconfers per 1 million children age 0-4 years, and between 37 Infection by the other enteroviruses usually confers and 589 per 1 million of the total population (Sabi resistance in a similar manner, but vaccines are not 19 per cen of paral epion tSe generally available. 1980). About 90 percent of paralytic episodes m these countries occurred during the first 3 years of life. Despite the fact that for various technical reasons these annual incidences are underestimates, they are similar Epidemiology to or considerably higher than the rates occurring in the USA in the immediate prevaccine era. These data During this century the incidence of poliomyelitis cast doubt on the belief that improved living has been observed to change from a constant conditions, in the absence of vaccination, increase the background infection to epidemics of increasing incidence of poliomyelitis disease. severity. In temperate climates these occur in late summer and early autumn. In the tropics and subtropics the fluctuations are less marked, but the Indftidual trend is the same. The reasons for this change are not fully understood but may be due to variations in Highly efficient vaccines are available for the three hygiene or other factors affecting virus transmission polioviruses. Both killed and live attenuated vaccines and so leading to variations in the resistance within the can be used. The live vaccine is probably preferable in community. In areas with poor hygiene children developing countries because it is easily administered acquire immunity while very young, and the pro- on a lump of sugar, whereas several injections are portion of paralytic cases is therefore low and confined required for the killed vaccine. The live vaccines to this age group. Disruption of this pattern of infection contain a mixture of attenuated (weakened) strains of may lead to a higher incidence of severe symptoms at a virus that establish an infection which leads to later period. Another possibility is that more virulent resistance but, unlike many of the wild strains, does not strains of virus have been introduced. infect the nervous system. These attenuated strains can Many of the other enteroviruses act in a similar also spread from person to person and so immunize a manner to poliovirus. Often serial waves of infection greater number of people but do not spread as move through the community, fading away to a very efficiently as the wild virus. The wild viruses are low or undetectable level and being replaced by suppressed but not eliminated from the community. It infection with another type of virus. Seasonal is therefore necessary to maintain the vaccination of variations also occur. young children to prevent the build up of a susceptible 138 ENVIRONMENTAL BIOLOGY & EPIDEMIOLOGY: VIRUSES group. Resistance appears 7-10 days after vaccination. is a rate process, and the removal of infectivity The response is sufficiently rapid to be of great benefit therefore depends on both the efficiency of removal and during an epidemic. No vaccines are available for the the numbers initially present. In feces and sewage these other enteroviruses. may be higher than 106 per gram and 106 per liter, No specific drugs are available either for chem- respectively. otherapy or prophylaxis. Good personal hygiene and The enteroviruses (chiefly polio, coxsackie, and the avoidance of contaminated food and water may echo), and to a lesser extent adenoviruses and reduce the risk of mild infection in early childhood but reoviruses, have been the only excreted viruses to be thereby increase the risk of severe infection later. extensively studied in the environment. This is partly because certain other important excreted viruses Environmental (particularly hepatitis A virus and rotavirus) cannot be routinely grown in cell culture at the present time. Improvements in excreta disposal alone are unlikely However, as laboratory skills improve, and as models to have a great impact. The highly infectious nature of for human excreted viruses are developed (for instance, viruses, the preponderance of young children among reoviruses and simian rotaviruses may provide models the cases, and the large proportion of symptomless for human rotaviruses), more data will be obtained on infections indicate that the main route of infection will the environmental behavior of excreted viruses other remain from person to person. The elimination of than the enteroviruses. Preliminary evidence from a excreta as a source of infection may change the primary few studies indicates that there may be significant means of transmission from the fecal-oral to the oral- differences between rotavirus, hepatitis A virus, and the oral route. Improvements in both general hygiene and enteroviruses in their environmental characteristics excreta disposal are likely to have an effect and may be (Farrah and others 1978: Wallis and Melnick 1967), responsible for the trend toward the epidemic type of although a recent study has shown that simian poliovirus transmission. In these circumstances in- rotavirus has survival properties in fresh and saline fection will probably be delayed rather than prevented, waters similar to enteroviruses (Hurst and Gerba and the proportion of patients with severe symptoms 1980). may increase. This can be prevented in the case of Throughout the rest of this chapter, data are poliomyelitis by the use of vaccines. presented on the numbers of viruses that researchers Polioviruses and other enteroviruses have been have isolated from various environmental samples. It isolated from flies and cockroaches. For instance, in must be stressed that these numbers depend very Texas (USA)polioviruses were isolated from 15 percent considerably on the techniques used; in general, as of flies, while coxsackieviruses were isolated from 45 techniques improve reported concentrations of en- percent, and flies experimentally fed polioviruses teroviruses from a particular source (for example, river continued to excrete them for up to 2 weeks (Melnick water) increase. The very earliest studies reported only and Dow 1953). It is clear from this and similar studies the proportion of samples from which viruses could be that insects can pick up viruses and may subsequently isolated-for instance, 62 percent of sewage effluent contaminate food, but it is unknown whether this mode samples contained enteroviruses. Subsequently, quan- of transmission is of any epidemiological significance titive techniques were developed that were based on (see chapter 37). observed cell death following inoculation with varying dilutions of sample, and these yielded a count of median tissue culture infective doses (TCID50) per Occurrence and Survival in the volume of sample. More recently, most laboratories Environment have adopted a technique whereby a direct count is made of plaques formed by viruses on cell monolayers, Viruses are not capable of multiplying outside of or in cell suspensions, which yields a count of plaque- living cells; therefore, in the environment their forming units (PFUS) per volume of sample. In both the numbers can only decrease. In favorable conditions, TCID and PFU techniques, counts depend upon the however, they can survive for months. Their survival is choice of cell line because different viruses will replicate aided by neutral pH and the presence of particulate or with varying readiness in different primate cells organic matter, moisture and, in particular, low (Schmidt and others 1978). temperatures. Resistance to inactivation varies con- When viruses are present in small numbers in large siderably among different types of virus and even volumes of sample, a variety of different methods can among different strains of the same virus. Inactivation be used to concentra te them. When viruses are bound ENTEROVIRUSES, POLIOMYELITIS, AND SIMILAR INFECTIONS 139 to each other in clumps, or are adsorbed to solid nonpolluted fresh water at 20°C and found that a 3 log particles, efforts must be made to disaggregate them. unit reduction occurred in 3 to > 14 days. For each Even adopting the most careful and sophisticated virus, survival times were similar in polluted and techniques, recovery of seeded enteroviruses from nonpolluted waters. The strong influence of tempera- environmental samples is typically below 60 percent. ture on enterovirus survival is illustrated by the To add to the complexity and uncertainty, results survival of 34 percent of enterovirus during 7.1 days of obtained are still too dependent upon the personal travel under the ice of a frozen 317 kilometer section of technique of the laboratory staff and the whole the Tanana River (Alaska, USA) (Dahling and tradition and routine of the particular laboratory. Safferman 1979). Quantitative data on viruses in the environment A number of workers (for instance, Cubbage and should therefore be taken as indicative only. others 1979, Katzenelson 1978, Young and Sharp Throughout this chapter concentrations are given as 1977) have noted that the observed loss of infectivity of viruses per volume or weight of sample although, viruses in water may be due in part to genuine damage strictly speaking, they should be as infective units or to the virus and in part to an artifact caused by many TCID5o or PFUS per sample. viruses aggregating and simulating a single infectious particle. This aggregation may involve the adsorption of viruses onto suspended particulate matter or it may Inl surface waters involve the formation of virus clumps. Enteroviruses can be isolated in low concentrations An important aspect of the behaviour and survival of from almost all surface waters receiving human wastes. viruses in natural waters is their tendency to become For instance, the Thames at London (UK) contains up adsorbed to organic or inorganic suspended particles. to about 100 enteroviruses per liter, with a peak usually Adsorption is enhanced at slightly acidic pH and in the occurring in winter (WHO 1979; the River Sowe (UK) presence of divalent cations and is deterred by the in December contained up to 620 enteroviruses per presence of soluble proteins (Schaub and Sagik 1975; liter (Morris and Waite 1980); the Missouri and Schaub, Sorber and Taylor 1974). Furthermore, Mississippi rivers (USA) have yielded up to 0.1 and 0.4 viruses adsorbed to solids retain their infectivity both enteroviruses per liter respectively; the Seine at Paris to tissue culture cells and mice (Moore, Sagik and and the Moselle at Nancy (France) have contained up Malina 1975; Schaub and Sagik 1975; Schaub, Sorber to 170 and 280 enteroviruses per liter, respectively and Taylor 1974). Adsorption to solids may cause an (Berg and Metcalf 1978). accumulation of viruses in bottom sediments, from Survival in water is dependent primarily upon which they may subsequently be resuspended in the temperature and the degree of contamination. Studies overlying waters. Wellings, Lewis and Mountain listed in the appendixes of Feachem and others (1980) (1976) isolated more than 15 excreted viruses per 100 show that at temperatures less than 10°C survival times grams of mud nearly 1 kilometer dowstream from a of between 24 and more than 272 days are reported, primary effluent discharge site. No virus was isolated while at temperatures above 20°C the range is 4 to 135 from the overlying river water at this site. days. In a study of enterovirus survival in the Rio There is very little evidence that the transmission of Grande (New Mexico, USA), at 23-27C, 90 percent enteroviruses during recreation in polluted surface inactivation occurred in 25 hours for poliovirus 1, 19 waters is of any public health importance. The spread hours for poliovirus 3, and 7 hours for coxsackievirus of adenovirus in swimming pools has been de- A13. At river temperatures of 4-8°C, the time for 90 monstrated or suspected in several investigations (for percent inactivation of poliovirus 1 was 46 hours instance, Heinz and others 1976). (O'Brien and Newman 1977). Niemi (1976) studied the In summary, a few enteroviruses may survive for survival of coliphage T7 in samples of Finnish river many months, although 90 percent reduction usually water and found that, after 64 days at 3°C, a 99.5 occurs within a few days, and 99 percent reduction percent reduction occurred, whereas after 64 days at within 1 month. Temperature is the single most 20°C a 99.98 percent reduction was recorded. Joyce determining factor and 99 percent reduction at 20°C and Weiser (1967) found that poliovirus did not survive may be expected within about 10 days. Survival is for more than 63-84 days at 20-25°C, but survived for longer in heavily polluted or in very clean waters. Very more than 91 days at 4°C when stored in samples of little data are available on virus survival in surface various farm pond waters. Hurst and Gerba (1980) waters in the tropics (Lund 1979), and more research is studied the survival of poliovirus 1, echovirus 7, required. Addy and Otatume (1976) isolated en- coxsackievirus B3 and simian rotavirus in polluted and teroviruses from 28 percent of surface water samples in 140 ENVIRONMENTAL BIOLOGY & EPIDEMIOLOGY: VIRUSES the Accra area (Ghana), with highest isolation rates (80 the sections below on survival in soil and on sewage percent) obtained from polluted street drains. treatment by septic tanks and land application. The However, because surface waters in the tropics are literature on viruses in groundwater has been reviewed typically in the temperature range of 20-30°C, it is elsewhere (Keswick and Gerba 1980). reasonable to expect that survival times will be considerably shorter than those generally reported In drinking water from temperate areas. Attention has been paid recently to the occurrence In groundwater- and epidemiological significance of enteroviruses in water supply systems (Anon. 1978: Committee on Enteroviruses have been isolated from groundwater, Viruses in Drinking Water 1979; EPA 1978; Mahdy especially in situatiorn where the groundwater is 1979; Melnick, Gerba and Wallis 1978; WHO 1979). shallow and sewage effluent or sludge has been applied Enteroviruses have been isolated in very low to the overlying soil. Survival of enteroviruses in concentrations from some treated, chlorinated water groundwater may be somewhat longer than in similar supplies in France, India, Israel, Italy, Rumania, South surface waters at the same location because in hot Africa, USA and USSR (Committee on Viruses in climates the groundwater is cooler than the surface Drinking Water 1979; Gamble 1979; Kott and others water (in cold climates the opposite may be true) and 1974; Melnick, Gerba and Wallis 1978: Rao, Lakhe groundwater is not exposed to sunlight. and Waghmare 1978; WHO 1979). A considerable Wellings and others (1975) demonstrated en- debate has developed over whether these very low virus teroviruses in shallow groundwater beneath a waste- concentrations in treated drinking water constitute a water irrigation site in Florida (USA) and showed that cause for concem on public health grounds. There is the viruses could survive in groundwater for at least 28 strong support, especially among environmental days. Wellings also reported a tentative association virologists in the USA, for the concept that, because between the pollution of groundwater by septic tank viral infectious doses may be very low, small numbers effluent and an outbreak of disease associated with of viruses in large volumes of drinking or recreational echovirus 22/23 complex at a migrant labor camp in water are important. It is postulated that viruses in Florida (Wellings, Mountain and Lewis 1976). Vaughn water may cause low-level transmission which remains and others (1978) reported low levels of virus undetected due to the large proportion of asympto- contamination (up to 3 viruses per liter) in wastewater matic infections and the varied symptomatology (table recharged groundwater on Long Island (New York, 9-1) in those individuals experiencing frank disease USA) at sites where recharge basins were located less (Berg 1967; Committee on Viruses in Drinking Water than 10 meters from the aquifer. This contamination 1979; WHO 1979). Some of those who take this view occurred despite the fact that all wastewaters had urge the adoption of stringent virus quality standards, undergone either chlorination or tertiary treatment by such as less than one infective unit per 40-100 liters in sand filtration. Slade and Edworthy (1981) isolated up recreational water and less than one infective unit per to 1.3 x 104 viruses per liter from groundwater in 100-1,000 liters in drinking water (Mahdy 1979; chalk beneath groundwater recharge lagoons receiving Melnick, Gerba and Wallis 1978; Shuval 1975; WHO raw comminuted sewage, but failed to detect viruses 1979). This school of thought has been influenced by from boreholes 120 meters and 400 meters downstream the unfortunate view that, because it is technically (in relation to groundwater flow) from the recharge possible to achieve a certain level of water purity, it is area. A study of groundwater pollution in Israel therefore desirable.' isolated enteroviruses in 20 percent of 99 samples and 1. For example. Melnick (1976) writes: "I suggest a... d in 12 samples enteroviruses were isolated in the maximum of one detectable virus unit per 10 gallons of recreational absence of fecal coliforms and fecal streptococci water and a maximum of one infectious virus unit per 100 gallons of (Marzouk, Goyal and Gerstreptococci drinking water. As our methods for detecting and monitoring water (Marzouk, Goyal and Gerba 1979). supplies have continued to improve, I would suggest that we can do Little is known about virus survival in groundwater, better, and raise the standards to a maximum of one infectious virus but estimates may be made from the data on survival in per 1,000 gallons ofc drinking water." Simtlarly, the WHO Scientific surface waters reported above. Yeager and O'Brien Working Group on Human Viruses in Water, Wastewater and Soil (1977) reported that a 90 percent reduction of concluded that "the presence of even a few enteric viruses in a large enteroviruses in groundwater occurred in 11 to 14 volume of drinking water should be prevented, since treatment measures exist to achieve this goal and detection techniques are days. Information on the travel of enteroviruses becoming available which can provide the required level of through soils to pollute groundwater is contained in monitoring" (WHO 1979). ENTEROVIRUSES, POLIOMYELlTIS, AND SIMILAR INFECTIONS 141 This point of view is refuted by others (especially likely that this was a wild strain of poliovirus. More European workers and those with an epidemiological data of this type are urgently required. perspective) who point out that there is no evidence for the existence of low-level waterborne transmission and that, even if it did exist, it might make no significant In seawater contribution to the maintenance of the endemicity of Many coastal communities discharge untreated or enterovirus infections (Gamble 1979). The authors of partially treated wastes into the sea. This is not only the this book support this second viewpoint. There is case in developing countries but is common practice strong epidemiological and theoretical evidence that throughout the world; for instance untreated sewage is enterovirus transmission is primarily by the person-to- discharged in large quantities at Honolulu and Miami person route2 and may indeed be oral-oral as well as Beach (USA) (Ruiter and Fujioka 1978; Edmond, fecal-oral. It is unlikely that very low concentrations of Schaiberger and Gerba 1978). The potential health enteroviruses in treated drinking water make any hazards are those of infection of bathers and marine epidemiologically significant contribution to trans- sportsmen and the contamination of shellfish. Recent mission3, and any decision on increased water quality advances in laboratory techniques have permitted the standards, implying increased treatment costs, must concentration of small numbers of viruses from large await evidence of the benefits to be expected from such volumes of turbid seawater (Payment and others 1976) a policy. This view is especially pertinent in developing and have encouraged a number of investigations into countries where there are severe shortages of both viral pollution of the marine environment. financial and technical resources. Edmond, Schaiberger and Gerba (1978) studied Some studies on the survival of enteroviruses in enterovirus contamination of seawater along the treated drinking water are listed in the appendixes of Florida coast (USA), an area of exceptional impor- Feachem and others (1980). One study (Lefler and Kott tance for marine recreation. Between Palm Beach and 1975) found that at 18-25°C 99.9 percent of Virginia Key there are 10 ocean outfalls discharging polioviruses were inactivated in 91 days in tap water and approximately 6 x I 05 cubic meters per day of raw and in 112 days in distilled water. At 4-8°C, poliovirus was treated sewage. The Miami Beach outfall discharges completely stable in tap water and distilled water for 231 1.8 x 105 cubic meters per day of untreated sewage at a days. Kott, Ben-Ari and Vinokur (1978) reporteda99.9 depth of 44 meters. The authors found enteroviruses at percent reduction of poliovirus after 80 days in tap the surface above the outfall at concentrations between water at 18-23cC. 21 and 42 infectious units per 400 liters. Fecal coliforms A quite distinct problem is that of enteroviruses in at this site were in the range 0.9-1.4 x 104 per 100 untreated and polluted drinking water. Very few data milliliters, and fecal streptococciwereO.5-4.9 x 10' per exist on virological aspects of water supplies in l00milliliters.AtMiamitheoutfalldischarges2 x 105 developing countries (Lund 1979), but the bacte- cubic meters per day of sewage treated by activated riological data indicate the probability of substantial sludge and chlorination at a depth of only 5 meters. At viral pollution of many sources. A study in Ghana this site between 0 and 3 enteroviruses per 400 liters (Addy and Otatume 1976) isolated enteroviruses from were detected, with fecal coliforms always less than 3 3 out of 8 water samples taken from 3 drinking water per 100 milliliters and fecal streptococci less than 33 per wells near Accra. Poliovirus 1 was isolated from one 100 milliliters. The marked difference in fecal pollution well and, since vaccination rates are extremely low, it is caused by discharging untreated and treated effluent was clearly demonstrated. 2. In this connection, it is unlikely that the assertion of Berg Loh, Fujioka and Lau (1979) reported that the city (1978a) that "the source of most of the viruses that infect man of Honolulu (Hawaii, USA) discharges 2.5 x 105 cubic through the oral route is wastewater" is true. There is certainly no meters of raw sewage per day into the Mamala Bay at a evidence to support it, whereas there is ample evidence of the point 3.2 kilometers from Ala Moana beach and 6.5 vigorous transmission of enteroviruses, particularly vaccine-derived kilometers from Waikiki beach. Up to 420 en- polioviruses, among members of the same household and especially terovir among very young children (see the subsection below on uses perlter were isolated from the sewage, and enteroviruses in feces and night soil). enteroviruses were isolated from the bay water at distances of up to 3.2 kilometers from the discharge 3. Further evidence of this is provided by unpublished data from ste.cAt om splingklocatios distan fromhthe Britain which shows that enterovirus levels in rivers and reservoirs site. At some samplmg locations distant from the (and therefore presumably in drinking water) tend to peak in winter, sewage outfall, enteroviruses were isolated from waters whereas enterovirus infections, and levels in sewage, tend to peak in which contained negligible numbers of fecal indicator late summer. bacteria. 142 ENVIRONMENTAL BIOLOGY & EPIDEMIOLOGY: VIRUSES Survival of enteroviruses in seawater is generally centration of enteroviruses was weakly but reported to be shorter than in freshwater. However, significantly correlated with rainfall, total coliform enteroviruses survive for longer in seawater than counts and salinity (accounting together for appro- coliform bacteria and there have been several reports of ximately 16 percent of the variance in the virus data). enterovirus isolations from seawater containing very Enteroviruses were isolated from 43 percent of few or no coliforms (Berg and Metcalf 1978). Won and recreational water samples judged acceptable by total Ross (1973) reported a 99.9 percent reduction of coliform standards (<1,000 per 100 milliliters), and echovirus 6 in aerated seawater after about 2 days at from 35 percent of shellfish-harvesting waters judged 22°C and after about 6-7 weeks at 3-5°C. The survival acceptable by total coliform standards ( < 230 per 100 in seawater was unaffected by the addition of organic milliliters). Similar studies in the same area are substances. Akin and others (1976) reported a 99.9 reported by Goyal, Gerba and Melnick (1978). percent reduction in poliovirus 1 in 5-6 days at 24°C in Studies of pollution in the Firth of Forth estuary the Gulf of Mexico. Fujioka, Lau and Loh (1978) (Scotland) revealed adenoviruses, coxsackieviruses, found a 90 percent reduction in poliovirus at 25°C in 1 polioviruses and echoviruses at two sites where median day in seawater collected close to the shore, and in 2-3 fecal coliform levels were 2.1 x 104 per 100 milliliters days in seawater collected farther out. Further and 4.2 x 103 per 100 milliliters (Watson 1977). experiments revealed the strong possibility of a specific Studies in an estuarine environment in the USA virucidal activity displayed by unidentified marine (salinity 0.9-2.8 percent, temperature 6-24°C) isolated microorganisms. In another study the same authors enteroviruses from 6 percent of water samples and 17 (Loh, Fujioka and Lau 1979) reported 90 percent percent of bottom sediment samples (Vaughn and reduction of poliovirus 1 in 2 days, and 99.9 percent Metcalf 1975). Survival experiments in the same study reduction in 4 days, in both sewage-contaminated and showed a 99 percent reduction in coxsackievirus B3 in sewage-free seawater at 24°C. about 12 days at summer temperatures (18-21°C), Considerable attention has focussed upon the study whereas this degree of reduction took approximately of enteroviruses in estuaries and the associated risk of 28 days during winter and spring (4-15°C). viral disease transmission via contaminated shellfish. Colwell and Kaper (1978) reported viral stability for Metcalf, Wallis and Melnick (1974) reported studies of 322 days at 4°C, whereas at 25°C viruses were rarely pollution of the Houston ship canal (temperature detected after 56 days. These results were unaffected by 10-33°C; salinity 0.1-1.1 percent; fecal coliforms salinity changes in the range 1 to 3.4 percent. Roberts, 6.6-500 x 103 per 100 milliliters) and Galveston Bay Haggerty and Johnson (1976) found that poliovirus 2 (temperature 9-30'C; salinity 1-2.4 percent; fecal suffered an 84-88 percent reduction after 20 days at coliforms <2-330 per 100 milliliters) in Texas (USA). 17°C when held in seawater, estuary water, river water Two activated sludge plants were discharging up to or lake water. Hurst and Gerba (1980) recorded a 99.9 1.7 x l0O enteroviruses per day into the ship canal, and percent reduction of poliovirus 1, echovirus 7, the dominant virus types identified were polioviruses 1 coxsackievirus B3 and simian rotavirus in estuarine and 2 and echovirus 7. In the ship canal, 0.8 kilometers water (temperature 20°C, salinity 1.2-2.8 percent) in downstream from the nearest effluent discharge site, 2-3 days. The rate of inactivation was unrelated to salt enterovirus concentrations were 0.05-0.9 per liter, concentration. The same virus types in clean and whereas 6.4 kilometers further downstream con- polluted freshwater at the same temperature were centrations were 0.08-0.7 per liter. Enteroviruses were reduced by 99.9 percent in 3 to > 14 days. The also isolated from the bottom sediments of the ship unimportance of salinity in determining virus survival canal at concentrations of up to 4 per 100 grams. In has been shown also by Berry and Noton (1976), Galveston Bay, 33 kilometers from the discharge site, Matossian and Garabedian (1967) and Metcalf, Wallis no enteroviruses could be detected in the water, but and Melnick (1974). polioviruses 1 and 2 were isolated from oysters Of particular relevance to recreational hazards are (concentrations up to 26 per 100 grams). Further the findings of Baylor and others (1977), which show examination of 89 poliovirus isolates from the ship that viruses can be transferred from surf to the air and canal and oysters indicated that 8 percent might be blown onto the beach. This is caused by viruses wild, virulent strains. Survival tests in the laboratory adsorbing to air bubbles as they rise through the water. indicated that, in ship canal water at 22°C, poliovirus 1, When they burst at the surface, tiny droplets rich in coxsackievirus B5 and echovirus 7 were eliminated viruses are ejected into the air and are carried on the within 21 days. Further studies in Galveston Bay wind. The concentration of viruses in these droplets (Gerba and others 1979) showed that the con- may be at least 100 times greater than in the seawater ENTEROVIRUSES, POLIOMYELITIS, AND SIMILAR INFECTIONS 143 from which they came. This presents a potential health of enterovirus excretion, are high. Otatume and Addy risk similar to that postulated for aerosol droplets (1975) isolated enteroviruses from 44 percent of 386 produced by activated sludge plants, spray irrigation fecal specimens collected from 45 healthy infants in systems and flush toilets (see the section below on the Accra (Ghana). Virus isolation rates were not affected occurrence and survival of enteroviruses in air). by seasons, were higher in urban (44 percent) than in A number of other studies (for instance, Gerba and rural (21 percent) areas, and were higher among infants others 1977; Hetrick 1978; Metcalf and Stiles 1968; from houses without flush toilets (50 percent) than Pietri and Breittmayer 1976; Shuval 1978; Vaughn and among infants from houses with flush toilets (30 others 1979a) have investigated enteroviruses in percent). Out of 138 typed virus isolates, 12 percent marine and estuarine environments and have reached were poliovirus (presumed to be wild), 4 percent were broadly similar conclusions. Survival in seawater is coxsackieviruses, and the remainder were echoviruses. generally shorter than in freshwater, and a specific In Ibadan (Nigeria) three separate studies showed 39 virucidal property of seawater (possibly of micro- percent of infants excreting enteroviruses or aden- biological origin) has been postulated. The evidence for oviruses (Montefiore and others 1963), 49 percent of this has been reviewed by Kapuscinski and Mitchell children under 3 years excreting enteroviruses other (1980) and Katzenelson (1978). Sunlight may have than polioviruses (Poliomyelitis Commission 1966), some slight virucidal action on viruses suspended near and 45 percent of children between 3 and 24 months the surface. Viruses are found associated with bottom excreting enteroviruses (Peradze, Montefiore and sediments in a greater proportion of samples, and at Coker 1968). In Yaounde (Cameroon), 39 percent of higher concentrations, than in the overlying waters, 524 children age 0-6 years were excreting en- and their survival is prolonged in this state (Gerba and teroviruses, and 11 percent were excreting polioviruses others 1977; LaBelle and Gerba 1979; Smith, Gerba (Boche, Millan and Le Noc 1973). Sabin and others and Melnick 1978; Vaughn and Metcalf 1975). (1960) found that 11 percent of children 1-5 years old Sediment may serve as a reservoir of enteroviruses that in Toluca (Mexico) were excreting wild poliovirus, may be resuspended into the overlying water by wind, while 51 percent were excreting other viruses. Rao, currents, dredging or boats. Lakhe and Waghmare (1978) reported that 45 percent Temperature is the most determining factor in viral of children between 1 and 15 years old in Nagpur survival, with greatly increased inactivation rates in (India) were excreting enteroviruses. These data on the warmer waters (Berry and Noton 1976; Colwell and prevalence of enterovirus excretion among children in Kaper 1978). Few or no data are available on marine Africa, Asia, and Central America show a quite pollution near major tropical coastal towns (Lund remarkable consistency. 1979). However, these towns typically discharge Another gauge of the very high incidence of considerable volumes of untreated or partially treated enterovirus infections among young children in wastes into the sea, and so substantial viral pollution is developing countries is data on the proportion of to be expected. Survival times are probably shorter unvaccinated children having antibodies to poliovirus. than those reported from temperate areas. For instance, John and Jayabal (1972) found that 79 percent of 191 unvaccinated infants and children under Infeces and night soil 5 years old in Vellore (India) had antibodies to one or more types of poliovirus, thus indicating a history of The source of enteroviruses in the environment is the infection. Sabin and others (1960) found that 100 feces of infected individuals, which may contain 106 or percent of children in Toluca (Mexico) developed more viruses per gram. There is extensive information antibodies to one or more polioviruses before the age of on the proportion of people, especially children, 4 years, and that over 90 percent of 4 year olds had excreting enteroviruses at a given time. Little is known antibodies to all three polioviruses. Montefiore and directly about the occurrence of viruses in night soil, others (1963) reported that 100 percent of children over although typical concentrations may be inferred from 3 years in Ibadan (Nigeria)had immunity to poliovirus 1. data on enteroviruses in feces (given here) and in In a subsequent study in Ibadan (Poliomyelitis sewage (given below). Enterovirus survival in feces and Commission 1966), the prevalence of immunity to night soil may be estimated from data on survival in polioviruses 1, 2, and 3 in children between 24 and 36 sludge (see below and the appendixes to Feachem and months old was 68, 48, and 68 percent respectively. others 1980). Studies in Kabul (Afghanistan) showed that over 90 Under conditions of poverty and poor hygiene the percent of unvaccinated children had acquired incidence of enteroviral infections, and the prevalence immunity to polioviruses by the age of 5 and that peak 144 ENVIRONMENTAL BIOLOGY & EPIDEMIOLOGY: VIRUSES transmission occurred in the early summer (Sery and a sewage especially rich in enteroviruses, and reported others 1970; Thraenhart and others 1970). concentrations of enteroviruses will continue to rise as By contrast, enterovirus isolation rates from laboratory techniques improve and as more studies are healthly individuals in industrialized countries are carried out in developing countries. Sewage in much lower. Froeschle, Feorino and Gelfand (1966) developing countries must be assumed to contain at isolated enteroviruses (excluding polioviruses, which least 105 enteroviruses per liter, and sewage effluents they assumed to be vaccine derived) from 4.9 percent of produced by conventional treatment plants will also healthy 1-5 year old children in six cities in the USA. contain high concentrations of enteroviruses (see the Isolation rates peaked in late summer and early fall section below on enterovirus inactivation by sewage with a maximum of 12.4 percent positive in September. treatment processes). Infection rates were higher in males than in females and In an early study of this subject, Bloom and others highest in 1 year olds, with rates decreasing with (1959) investigated the enteroviruses in the sewage of increasing age. Cooney, Hall and Fox (1972) studied Lansing and East Lansing (Michigan, USA) between over 14,000 fecal specimens in Seattle (USA) and found 1955 and 1957. East Lansing sewage yielded en- polioviruses (presumed to be vaccine derived) in 8.8 teroviruses in 14 percent of samples, compared with 7 percent, adenoviruses in 2.2 percent, coxsackieviruses percent in Lansing, which had large volumes of in 0.7 percent, and echoviruses in 0.6 percent. From industrial wastes in its sewage. Peak isolations 18,000 respiratory specimens, polioviruses were isol- occurred during July through November. Thirty-three ated in 0.8 percent, adenoviruses in 0.9 percent, percent of samples of influent at the East Lansing coxsackieviruses in 0.1 percent, and echoviruses in 0.5 activated sludge plant were positive for enteroviruses, percent. Isolation rates were inversely related to age. while only 10 percent of samples of the final effluent In summary, it is clear that enteroviruses spread were positive. vigorously by the fecal-oral route (and possibly also by Haifa (Israel) sewage between 1972 and 1974 the oral-oral route) in conditions of poverty and low contained a monthly average of between 6 x I03 and personal and domestic hygiene. Thus the prevalence of 4.9 x 105 viruses per liter. The highest value recorded enterovirus excretion is high (40-50 percent among was 1 x 106 viruses per liter (Buras 1976). Fattal and infants and young children), as is the prevalence of Nishmi (1977) reported a predominance of po- antibodies to enteroviruses, which indicate past or lioviruses amongst enteroviruses isolated from the current infection. Under conditions of relative sewage of six Israeli towns and found that 13 percent of affluence and optimal hygiene (as in the USA) wild isolated polioviruses were wild strains rather than enteroviruses, and vaccine-derived polioviruses, con- attenuated vaccine strains. By contrast, Katzenelson tinue to circulate in the community and among and Kedmi (1979) reported detecting poliovirus in members of the same family. However, the prevalence only about 50 percent of 25 samples of raw sewage and of enterovirus excretion is very much lower (around 5 sewage effluents in Jerusalem, Tel Aviv and elsewhere percent in young children) than in the developing in Israel. The proportion of polioviruses to all countries. In all countries studied, the prevalence of enteroviruses was low. virus excretion is inversely related to age, so that the In Seattle (USA) Heyward and others (1979) highest virus excretion rates are found among infants. isolated up to 1.3 x I03 viruses per liter from combined As hygiene improves in the absence of vaccination sewer-stormwater overflows. In Ottawa (Canada) programs, the age distribution of infections tends to Sattar and Westwood (1977) detected pathogenic shift upwards, and the amount of clinically serious viruses in 79 percent of sewage samples. Of 72 isolates disease may increase (see, for instance, Anon. 1971, identified, 56 (78 percent) were reoviruses; the Hillis 1979, Metselaar 1968). remaining 16 were enteroviruses. Of the 16 en- teroviruses, 1 was coxsackie, 10 were vaccine strains of In sewage poliovirus, and 5 were wild polioviruses. The authors point out that the presence of these wild strains in Since enteroviruses are not normally excreted for sewage, at a time when immunity against poliovirus is prolonged periods by healthy individuals, their declining due to a fall-off in vaccination, is a cause for occurrence in sewage is subject to wide fluctuations. concern. Fujioka and Loh (1978) isolated en- However, nearly all sewages contain enteroviruses, and teroviruses from 100 percent of raw sewage samples the larger the contributing population the less variable investigated in Hawaii (USA) at concentrations is the concentration of viruses. Communities with poor between 27 and 1.9 x 104 per liter. In the same study, hygiene and a high proportion of children will produce 26 poliovirus isolates were assayed for virulence and 3 ENTEROVIRUSES, POLIOMYELITIS, AND SIMILAR INFECTIONS 145 (all from chlorinated effluent) were found to be wild. enteroviruses per liter (maximum 218 per liter). This Rao, Lakhe and Waghmare (1978) reported virus difference was attributed to the differences in socioecon- concentrations of up to 11,500 per liter in Indian raw omic status and age structure between the two sewage. There was a pronounced diurnal and seasonal communities. Enteroviruses in sewage reflect the levels variation in virus load; maximum concentrations of infection and vaccination within the contributing occurred between 8 and 10 a.m. and during the rainy population and may be used as an aid to epidemiological season. Nearly 80 percent of viruses isolated were surveillance (see, for instance, Zdrazilek, Sramova and polioviruses and 60-80 percent of these were wild Hoffmanova 1977). strains. The authors noted that about 60 percent of Little information is available on the concentration recorded cases of paralytic poliomyelitis cases in India of enteroviruses in tropical sewage. It is to be expected are reported during the rainy season. that poor communities, living in conditions of Virus survival in sewage has been investigated in inadequate hygiene, will produce a sewage with 107 or several studies (see the appendixes of Feachem and more infectious virus units per liter (Lund 1979), others 1980). The results generally indicate longer although, of course, most such communities produce survivals than in river water, with survival times of over no sewage at all because they are not connected to a 231 days at cool temperatures (< 10°C) and up to 110 sewerage system. However, even fairly affluent days at warmer temperatures (20°C). Lefler and Kott communities in developing countries will almost (1975) showed 99.9 percent reduction of poliovirus in certainly produce a sewage with a greater con- sewage, after 42 days at 18-25°C, and after 231 days at centration of pathogenic viruses than in Europe and 4-8°C. Kott, Ben-Ari and Vinokur (1978) reported the North America, because the incidence of viral complete disappearance of enteroviruses in lagooned infections is higher, water use is lower, and a greater trickling filter effluent within 73 days, and the proportion of the population is under 15 years old (see disappearance of poliovirus in oxidation pond effluent the previous section on viruses in feces). at 18-23°C within 110 days (99.9 percent reduction in about 70 days). Rao and others (1977) found up to In sludge 1,250 enteroviruses per liter in Bombay sewage and report that, when stored at 8°C for 2 days, a 22 to 40 The sludges of sewage works are rich in en- percent loss occurred. teroviruses because a high proportion of viruses in Prolonged survival of enteroviruses in sewage may sewage are, or become, solids associated and are be due in part to the protective effects of adsorption to therefore concentrated into both primary and secon- solids. Wellings, Lewis and Mountain (1976) found dary sludges (Lund 1973,1976; Lund and Ronne 1973; that between 16 and 100 percent of viruses in raw Wellings, Lewis and Mountain 1976). It is probable sewage and sewage effluent, at two treatment plants in that most of the difference between the virus Florida (USA), were solids associated. Gerba, Stagg concentration of the influent and the effluent of a and Abadie (1978) reported that 3 to 49 percent of sewage treatment plant is accounted for by the viruses viruses were solids associated in treatment plant in the sludge. The few studies on virus survival in sludge effluents near Houston (Texas, USA). are listed in the appendixes to Feachem and others In a unique study Ruiter and Fujioka (1978) (1980). investigated the sewage produced by two communities Subrahmanyan (1977) studied the survival of several in Honolulu (Hawaii, USA). Kuhio Park Terrace had a types of enteroviruses added to sewage sludge at a total population of 2,745, of whom 46 percent were concentration of 107 per liter and kept at 22°C. children under 14 years. The density of settlement was Survival times ranged from a minimum of 2 weeks 376 persons per hectare, 73 percent of households had (coxsackievirus A9) to a maximum of over 12 weeks an income of under US$5,000 per year, and 23 percent (coxsackievirus B5 and echovirus 9). Polioviruses of heads of household were unskilled laborers. Nuuanu survived from 8 to 12 weeks. Damgaard-Larsen and had a total population of 2,302, of whom 10 percent others (1977) inoculated digested and dewatered were children under 10 years. The density of settlement sludge with coxsackievirus B3 at a concentration of 106 was only 19 persons per hectare, 4 percent of per gram. The sludge was applied outdoors in households had an income of under US$5,000 per year, Denmark to sandy and clay soils during December to and 4 percent of household heads were unskilled May, when rainfall totalled 300 millimeters and laborers. Kuhio Park Terrace produced a sewage with temperatures ranged from -12 to 260C. Virus an average of 345 enteroviruses per liter (maximum 820 inactivation took place at a rate of about 1 log unit per per liter), while Nuuanu produced an average 93 month, and it took 23 weeks before viruses could not be 146 ENVIRONMENTAL BIOLOGY & EPIDEMIOLOGY: VIRUSES detected. Viruses remained bound to the sludge and by low temperatures but was unaffected by whether the did not travel downward through the soil. Nielsen and soil was wetted with distilled water or with various Lydholm (1980) reported the survival of naturally concentrations of sewage effluent. Virus inactivation occurring coxsackievirus B5 for 4 months occurred much more rapidly under nonsterile aerobic (March-July) in digested sludge applied to land in conditions than under sterile aerobic conditions or Denmark. under sterile and nonsterile anaerobic conditions. Sattar and Westwood (1979) studied the viruses Duboise, Moore and Sagik (1976) found that present in raw sludge (5 percent solids), anaerobically polioviruses held for 84 days in loamy sand were digested sludge (20 days at 35°C), and lagoon-dried reduced by less than 90 percent at 4°C but by 99.999 sludge (minimum of 6 months drying time) from the percent at 20°C. In studies into the disposal of septic largest sewage treatment plant in Ottawa (Canada). tank effluent it was found that poliovirus 1 adsorbed to Excreted viruses were isolated from 84 percent of raw sandy soils was reduced by 97.5 percent after 28 days at sludge samples, 53 percent of digested sludge samples, 20°C and by less than 50 percent after 56 days at 7°C and 39 percent of dried sludge samples. Viruses were (Small Scale Waste Management Project 1978). isolated from sludge that had been drying for over 8 Lefler and Kott (1974a) studied the survival of months. Most virus isolates were reoviruses, the poliovirus 1 in sand kept in the dark at room remainder being enteroviruses. temperature (18-22°C). With the sand saturated in Hurst and others (1978) isolated viruses from distilled water, no poliovirus was detected after 112 various activated sludge samples at a sewage treatment days, and 99 percent inactivation was achieved in plant at Houston (Texas, USA) in concentrations of about 63 days. With tap water or oxidation pond around 30 viruses per liter of sludge. After sludge effluent, complete inactivation took 105 days, while 99 thickening, aerobic digestion and centrifugation the percent reduction took 42 days. Coliphage f2 survived concentration of viruses rose to 231 per liter. This for longer than poliovirus 1. When the saturated sand sludge was then applied to land, where the virus was kept at 4-8°C, 20 percent of poliovirus was still concentration was monitored over two separate active after 175 days. On dried sand at 4-8°C, 96 periods. During the first 7 day period (during percent inactivation occurred in 21 days and virus was September with no rain), the solids content of the still detectable (at 0.02 percent of the original sludge rose from 6.9 to 18.4 percent, and 97 percent of concentration) after 77 days. the viruses were inactivated. During the second 7 day Tiemey, Sullivan and Larkin (1977) inoculated period (during September with rain on day 6), the poliovirus 1 into samples of activated sludge and solids content of the sludge stayed almost constant at secondary effluent to produce a viral concentration of 13-14 percent, and 99.5 percent of the viruses were 2.5 x 108 viruses per liter. The fluids were sprayed over inactivated. A sample of sludge which had been on the soil plots so as to flood them to a depth of 25 field for 3 months had a solids content of 59 percent millimeters. Runoff water from the plots contained 106 and no demonstrable virus. Thus in a Texas summer a viruses per liter on the day of flooding but this fell to 0 2 log reduction per week was recorded, compared with by day 6. In winter (- 14 to 27°C) viruses applied in a unit log reduction per month during a Danish winter effluent survived in soil for between 89 and 96 days, (Damgaard-Larsen and others 1977). whereas viruses applied in sludge survived between 96 and 123 days. In early summer (19°C to 34°C), viruses In soil were not detected for more than 11 days after flooding with either effluent or sludge. Increased interest in the health aspects of the Yeager and O'Brien (1979a) elucidated several agricultural use of sewage and sludge has generated aspects of virus survival in soil. They found that several studies on virus survival in soil. However, little poliovirus survival was heavily temperature de- information is yet available. More is known about pendent, with virus survival in saturated soil being up virus travel and adsorption in soils, and this subject is to 12 days at 37°C, up to 92 days at 22°C, and up to 180 reviewed below in the section dealing with land days at 4°C. Viruses survived longer in soils saturated treatment. with septic tank liquor (90 percent reduction in 8-21 A review by Gerba, Wallis and Melnick (1975a), and days at 22°C) than in soils saturated with river or the studies listed in the appendixes to Feachem and groundwater (90 percent reduction in 5-7 days at others (1980), indicate that survival times of over 175 22°C). Viruses survived for longer in sandy loam (90 days are possible. Hurst, Gerba and Lance (1979) percent reduction in 6-21 days at 22°C) than in sand found that enterovirus survival in soil was prolonged (90 percent reduction in 4-8 days at 22°C). Soil drying ENTEROVIRUSES. POLIOMYFLITIS. AND SIMILAR INFECTIONS 147 was found to be highly virucidal, irrespective of soil the survival of various viruses on strawberries, cherries, type, and speed of soil drying depended on and peaches at 4°C and investigated the effect of temperature. Soil moistures of below 2.9 percent inoculating the viruses in water or in dilute feces and of appeared to be especially virucidal. In an accompany- storing the fruit in humid or dry atmospheres. Viruses ing study (Yeager and O'Brien 1979b) the same were inactivated far more rapidly under dry than under authors investigated the nature of virus inactivation in humid conditions, and virus survival was prolonged by soil. They concluded that loss of infectivity is due to inoculation in feces rather than in water. Viruses irreversible damage to the virus particles. They survived longer on cherries and peaches than on speculate that two general mechanisms may underly strawberries, and coxsackieviruses and echoviruses the inactivation of picornaviruses in the environment: survived for longer than polioviruses and reoviruses. under temperate, saturated conditions RNA de- Under dry conditions survival of viruses was between gradation may occur, whereas in dried soil (and also 40 and < 1 percent after 1-2 days, and viruses were perhaps in aerosols and under a variety of hostile undetectable after 4-6 days. The short survival times circumstances such as heat, irradiation and de- are notable in view of the cool temperature (4°C), and siccation) the virions may dissociate into intact RNA the authors consider that an antiviral substance and isoelectrically altered capsids (see also O'Brien and produced by the fruit is active. The authors also Dacus 1978). consider that the longer survival of viruses inoculated Virus survival in soil depends upon many factors in dilute feces is due to delayed desiccation as including the type of soil, its pH, the sterility of the soil, compared with viruses inoculated in water. and the type of liquid in which the viruses are applied. Subsequently, the same authors (Konowalchuk and However, temperature and moisture appear to be the Speirs 1977) reported that the concentration of dominant factors. While very long virus survival times poliovirus 1 and coxsackievirus B5 was reduced by (over 5 months) are possible at cool temperatures about 99 percent after 5 days on grape bunches hung (< 10°C), at warmer temperatures (> 25°C) viruses are indoors at 22°C. likely to be eliminated within 2 weeks. Soil drying is Kott and Fishelson (1974) investigated the effect of also highly virucidal, and the evidence suggests that, in effluent chlorination and sunlight on the survival of warm climates, intermittent agricultural application of seeded poliovirus 1 on tomatoes and parsley. The sewage, night soil or sludge, with drying periods of 3-5 maximum recoveries of polioviruses from vegetables 6 days between applications, would result in little or no hours after application in waste stabilization pond build-up of viable pathogenic viruses in the soil. This effluent were: 2.2 percent when applied in un- contention is further supported by the studies of chlorinated effluent with exposure to sunlight, 1.6 Sadovski and others (1978)-reported in the next percent when applied in chlorinated effluent with subsection, concerning viruses on crops. exposure to sunlight, 12.7 percent when applied in unchlorinated effluent and kept in darkness, and 8.5 percent when applied in chlorinated effluent and kept On crops in darkness. Poliovirus applied outdoors did not survive for more than 1 day on tomatoes or 2 days on The interest in virus survival in soil has been parsley at 15-31°C. Poliovirus survival was con- accompanied by interest in virus occurrence and siderably prolonged when viruses were applied in survival on vegetables fertilized or irrigated with sludge phosphate-buffered saline rather than effluent. or sewage. Larkin, Tierney and Sullivan (1976) planted lettuces Konowalchuk and Speirs (1975a) studied virus and radishes and, 8-10 days later, sprayed them with survival on vegetables stored at 4°C. In a humid secondary effluent or sludge seeded with 2.5 x 108 atmosphere, coxsackievirus, poliovirus, echovirus, polioviruses per liter. These experiments were con- reovirus, and adenovirus inoculated in a water droplet ducted in Ohio (USA) in the summer of 1973 and 1974 onto lettuce, celery, green peppers, tomatoes, radish, when there was extensive direct sunlight, periodic rain, and carrots were undetectable after 4-5 days. When air temperatures of 19-340C, and soil surface inoculated in dilute feces, 4-5 percent were detectable temperatures rising to 45°C. On the days immediately after 5 days; when inoculated in feces, 7-12 percent after spraying, large amounts of virus (up to 2.9 x 104 were detectable after the same time. Additional studies per 100 grams) could be recovered from the vegetables. on virus survival in vegetable infusions indicated that Two weeks after spraying no more than 100 viruses per the vegetables contained no antiviral agents. In a later 100 grams could be detected, and small numbers (10 study Konowalchuk and Speirs (1975b) investigated per 100 grams) persisted for at least 36 days. In similar 148 ENVIRONMENTAL BIOLOGY & EPIDEMIOLOGY: VIRUSES studies, Tierney, Sullivan and Larkin (1977) were still Feachem and others (1980)4, indicate highly variable able to isolate 60 polioviruses per 100 grams of lettuce survival times for enteroviruses on vegetables and fruit. 23 days after spraying. (Lettuces and radishes in this Type of virus and type of crop are clearly important, climate are normally harvested 3 to 4 weeks after but the dominant factors are temperature, sunlight and planting.) humidity (which will control the degree of warming), Sadovski and others (1978) studied the survival of and radiation and desiccation experienced by the polioviruses inoculated into waste stabilization pond viruses. Survival times of up to 2 months are possible, effluents and applied by drip irrigation to cucumber but at day temperatures above 25°C (and especially in plots on two farms in Israel. At one site (air dry climates) one may anticipate negligible survival of temperature 13-30°C, soil temperature at noon enteroviruses on crops for more than 2 weeks. Indeed, 22-30°C, sunlight 9.5 hours per day, relative humidity it may be that almost complete elimination will occur 27-55 percent), a single irrigation was performed with in under 5 days and that the longer survival times inoculated effluent containing 9 x 107 polioviruses per reported by some investigators are only achieved by liter. Viruses were still detectable in the irrigation the untypically high concentration of seeded en- system, at a concentration of > 104 per liter, 8 days terovirus in the applied effluent [for instance Larkin, after the flow of inoculated effluent. The soil Tierney and Sullivan (1976) employed 2.5 x 108 contamination immediately after irrigation with polioviruses per liter, and Sadovski and others (1978) inoculated effluent was l04viruses per 100 grams ofsoil had 2.2 x 1012 per liter]. It has been clearly (dry weight) and persisted at a level of > 103 per 100 demonstrated by Israeli workers that drip irrigation, grams for at least 8 days. Cucumbers grown in exposed particularly when combined with soil covered with soil were contaminated by 2.2 x 103 viruses per 100 plastic sheets, is a method of effluent application that grams immediately following irrigation, and this minimizes the risks of crop contamination by contamination fell to 30 per 100 grams on day 8. enteroviruses. However, when the soil and drip lines were covered with plastic sheets no viruses could be isolated from the I cucumbers after a few hours had elapsed after Infshand .1o,!/ti .',' inoculated irrigation. At the second site (air tempera- The primary hazard associated with estuarine and ture 23-28°C, soil temperature at noon 40-43°C, marine discharge of fecal wastes may not be risks to sunlight 11.8 hours per day, relative humidity 62-70 bathers and water sportsmen but to those who eat the percent), three irrigations were performed with fish and shellfish that are harvested in polluted waters. inoculated effluent containing 2.2 x 1012 polioviruses The greatest risks of viral infection are associated with per liter. After the third inoculated irrigation the soil the ingestion of contaminated molluscs (such as contained 9.1 x 103 viruses per 100 grams (dry oysters, mussels, cockles, and clams) and crustacea weight), and this contamination fell to 47 per 100 (such as crabs, lobsters, shrimps, and prawns) in a raw grams after 10 days and to O after 15 days. Unlike at the or partially cooked state. Most attention has focussed first site, where irrigation with uninoculated effluent upon oysters because they are commonly eaten raw had continued throughout the study, in this case and their method of filter feeding (common to all irrigation terminated 5 days after the third inoculated bivalve molluscs) concentrates pathogenic organisms irrigation, and consequently the soil moisture content from the water into their tissues (Anon. 1976; Gerba fell from 15 to 3 percent. Virus contamination of the and Goyal 1978; Hughes, Merson and Gangarosa cucumbers grown in exposed soil rose to 0.13 per 100 1977; Metcalf 1978; Wood 1979). Attention has also grams, but was undetectable 6 days after the last been paid to improved laboratory techniques for inoculated irrigation. In covered soil no viral isolating enteroviruses from shellfish (Gerba and contamination of the vegetables could be detected. At Goyal 1978; Metcalf 1978; Vaughn and others 1979b). both sites, virus survival in the soil was unaffected by Mitchell and others (1966) placed 600 eastern whether plastic sheets were lain over the soil and the oysters (Crcassostrea virginica) in seawater at 20°C drip lines. Earlier studies at the first site by the same containing 106 polioviruses per liter and found that workers (Sadovski, Fattal and Goldberg 1978) showed viruses rapidly accumulated in the oyster tissue such that no viruses could be isolated from cucumber or that after 1 hour the virus concentration in the oyster eggplants drip-irrigated with uninoculated waste was 27 times higher than in the surrounding water. stabilization pond effluent containing 103 entero- viruses per liter. 4. See also Engley (1956) and Berg (1978b) for reviews of literature These studies, and others listed in the appendixes of on virus survival in food (as opposed to on cropsJ. ENTEROVIRUSES, POLIOMYELITIS, AND SIMILAR INFECTIONS 149 When the seawater contained 3 x 105 polioviruses per harvesting waters in Galveston Bay (Texas, USA). Of a liter, viruses accumulated less rapidly but were always total of 44 water samples, 26 yielded viruses in concentrated in the oyster by at least 10-fold after 3 concentrations of up to 0.4 per liter, whereas of 40 hours. When the oysters were rinsed and placed in pools of 10 to 12 oysters each, viruses were isolated sterilized seawater, over 95 percent and 99.9 percent of from 14 pools at concentrations of up to 224 per 100 viruses were eliminated after 8 and 24 hours grams. On five occasions viruses were found in oysters respectively. Viruses were sometimes undetectable but not in the overlying waters. Gerba and Goyal after 48 hours and sometimes detectable in very small (1978) reviewed 17 reported isolations of viruses from numbers (2 per gram) for up to 96 hours. shellfish. Hoff and Becker (1969) studied the accumulation of It is generally agreed that no human enterovirus poliovirus by the Olympia oyster, the Pacific oyster, multiplication takes place in shellfish (Chang and and the Manila clam and found that these species others 1971) and that the dangers lie in the uptake, concentrated the virus to a level between 10 and 180 concentration, and survival of viruses in shellfish tissue. times higher than in the surrounding waters. When the Uptake, depuration, and survival in oysters has been contaminated shellfish were held in disinfected found to be temperature dependent. Below a given seawater (6-16°C), poliovirus concentrations in the temperature, a particular species of shellfish will cease meat were reduced by at least 99.9 percent after 96 to filter. The European flat oyster (Ostrea edulis) hours. Hedstrom and Lycke (1964) found that appears to filter at temperatures down to 5°C, whereas poliovirus survived for 3.5 days in seawater but for well the eastern oyster (Crassostrea 0irginica) will not filter over 6 days in oysters in contaminated seawater. below 7°C. The edible mussel (Mytilus edulis) filters at Oysters did not cleanse themselves of poliovirus within temperatures down to 2°C, but the hard clam 22 hours when transferred to uninfected water or to (Mercenaria mercenaria) ceases active filtration at water containing up to 1.7 milligrams per liter of free about 12°C (Metcalf and Stiles 1968; Wood 1979). As chlorine. the temperature falls, the rate of filter feeding declines DiGirolamo, Liston and Matches (1975) placed and so does the rate of accumulation of viruses. Below oysters in seawater (salinity 2.8 percent, temperature the critical temperatures mentioned above, virus 13°C) containing 1.9 x 107 polioviruses per liter and accumulation should cease. The same is true of found that after 2 days the oysters had accumulated depuration, and so a contaminated shellfish will about 104 polioviruses per gram of meat. Most viruses cleanse itself more slowly as temperature falls and will were concentrated in the digestive organs and feces. cease to cleanse itself at all below a critical temperature. When placed in stationary sterilized seawater (salinity Survival of viruses in stored shellfish is very much 2.8 percent, temperature 13°C), contaminated oysters prolonged by low temperatures. Vaughn and Metcalf lost between 79 and 84 percent of polioviruses in 5 (1975) reported that coxsackievirus B3 in oysters days. When placed in flowing sterile seawater, oysters survived for up to 42 days at 1-11°C, but for only 22 lost over 99 percent of accumulated poliovirus after 3 days at 14-21°C. Metcalf and Stiles (1965) found that days. Gerba and Goyal (1978) reviewed 17 other viruses in oysters stored at 5°C remained relatively studies on the accumulation and depuration of stable for at least 28 days. DiGirolamo, Liston and excreted viruses by shellfish. Matches (1970) found that 10 percent of polioviruses The isolation of enteroviruses from oysters living in survived for 84 days in oysters after freezing at - 36°C lightly contaminated waters has been frequently and storage at - 17.5°C. DiGirolamo and Daley reported. Metcalf and Stiles (1965) isolated coxsackie (1973) froze crabs at -20°C and found that 17-35 B4 and echo 9 viruses from oysters in estuary waters at percent of seeded coliphage T4 survived after 30 days. distances of up to 4 miles from the nearest sewage Other studies of viruses in refrigerated shellfish have outlet. Vaughn and Metcalf (1975) found that 7.6 shown that survival times of up to 120 days are possible percent of oyster samples contained enteroviruses in (Gerba and Goyal 1978). waters from which only 5.6 percent of samples were These and many other studies (reviewed in Gerba and positive for viruses. Vaughn and others (1979a) Goyal 1978) show that viruses in water are readily isolated up to 30 viruses per 100 grams of flesh from accumulated by shellfish. In edible bivalve molluscs clams in Great South Bay (New York, USA), the (clams, mussels, oysters) the viruses are concentrated waters from which contained no more than 2 viruses mainly in the digestive system and may be present in per liter. concentrations over 100-fold higher than in the Goyal, Gerba and Melnick (1979) studied the surrounding waters. This is because these shellfish are presence of enteroviruses in oysters and oyster- filter feeders, and one oyster may filter as much as 1,500 150 ENVIRONMENTAL BIOLOGY & EPIDEMIOLOGY: VIRUSES liters of seawater per day in its quest for food. Crustacea In the air that inhabit polluted waters or that feed on Airborne droplets of water and wastewater may contaminated molluscs may also accumulate en- contain enteroviruses, and these viruses may cause teroviruses, although less work has been done on this, infection when inhaled. Droplets containing viruses DiGirolamo and others (1972a) showed that crabs kept m in contaminated seawater for 2 days at lO°C, or allowed may be formed by the flushing of a toilet, by spray to feed on contaminated mussels for 12 hours, irrigation, or by any occasion in which bubbles are tocumufeted onrcontamoina ussels for 12 hours, rising through contaminated waters and bursting at Depuration or cleansing of viruses from shellfish is a the surface (such as activated sludge plants, waves and Deph a ti on p or leasin g of res filr or sheli sh is a surf, or the passage of boats). As a bubble rises through mechanical process induced by the filter feeding of the wtrvrssbcm dobdt t ufc h mollusc in clean water. Maximum depuration occurs water, viruses become adsorbed to its surface. The when feeding activit is.greatest.This bubble bursting at the surface ejects a tiny jet of water when feeding activity is greatest. Thus, cleansing thtbek1nomnSrplt,adteedolt more rapid at warmer temperatures, at optimal that breaks mto many droplets, and these droplets s ies rand in flowi n water.epuat o ftim contain most of the viruses that were adsorbed to the salInities, and in flowing water. Depuration of bubble. Thus the droplets contain a much higher commercially harvested oysters by placing them in concentration of viruses than the water from which clean water is practiced. Chlorination of the water to came. maintain its purity has been advocated, but this is Bey came. .. ... .. ,.' , ...... Baylor, Peters and Baylor (1977) bubbled air antagonistic to the oyster, inhibits feeding, and thus through a column of liquid containing coliphages T2 delays depuration. Preliminary experiments have been and T4 and produced droplets that contained a conducted on virus removal from contaminated conduted prion virus taqcuuremoa from adsorintminted t concentration of phage 50 times that in the column. seawater prior to aquaculture by adsorbing viruses to Baylor and others (1977) seeded the breaking surf with magnetite and removing them in a magnetic field coliphages T2 and T4 at beaches near New York. (Bitton and others 1977). Droplets were formed in the surf that contained a When contaminated shellfish reach the market, the concentration of phages 100 to 250 times higher than risks are obviously greatest if they are eaten raw. the seawater, and these droplets were carried by the However, a residual risk remains even with cooked the forwateand m ets. shellfish. Studies have shown that a proportion of wi o at least 30 meters. . * r. r ~The aerosohized excreted viruses most encountered polioviruses in oysters survived stewing (after 8 by people in developed countries are those produced minutes, 10 percent survived), frying (after 10 minutes, by the flush toilets in their houses. Gerba, Wallis and 13 percent survived), baking (20 minutes, 13 percent Melnick (1975b) seeded 108 polioviruses into a toilet survived), steaming (30 minutes, 7 percent survived), bowl and found that flushing ejected at least 2.8 x 103 and irradiation (4 kilogray,5 7-13 percent survived) infectious units to the level of the seat. Further and that up to 20 percent of coliphage T4 in crabs experiments with seeded coliphage MS2 showed that survived boiling (DiGirolamo, Liston and Matches survived boiling (DiGirolamoand Listhers 1972b. Mthese organisms remain airborne long enough to settle 1970, 1972; DiGirolamo and others 1972b). out in large numbers on surfaces throughout the Nearly all the documented disease outbreaks bathroom, and presumably also to be inhaled by associated with excreted virus contamination of people in the bathroom. In an unventilated bathroom, shellfish are outbreaks of hepatitis A (see chapter 10) or 94 percent of recovered coliphage had settled out viral gastroenteritis (see chapter 11). These outbreaks within 2 hours of the flush, and most of the remainder have been reviewed by Gerba and Goyal (1978) and had settled within 4 hours. Small numbers of viruses Levin (1978). However, as reported above. most studies on viruses in shellfish have focussed on the ould apparently remain airborne for much longer. enteroviruses because it is for these viruses that well- Fanmno and others (1977) studied airborne viruses developed laboratory isolation methods exist. Before produced by a trickling filter plant and an activated A. sludge plant in Michigan (USA). The naturally the development of isolation techniques for hepatitis A occurring level of animal viruses in sewage at the virus and rotavirus, it must be assumed that these trickling filter and activated sludge units was 100 per viruses behave in shellfish similarly to the en- liter, while the coliphage concentration was 5 x 105 per liter. No animal viruses were recovered from air samples at the plants,-but coliphage was recovered at concentrations up to 0.5 per cubic meter of air. 5. The Si unit ofradiation dose is the Grav' Gy), which is equal to Airborne coliphage recovery was correlated with 100 rads and is the equivalent of 1 joule per kilogram. relative humidity (higher humidity associated with ENTEROVIRUSES, POLIOMYELITIS, AND SIMILAR INFECTIONS 151 higher recovery) but was not correlated with wind Inactivation by Sewage Treatment speed or ambient temperature (see also Cochran and Processes Fannin 1976 and Fannin and others 1976). Earlier laboratory studies by de Jong and Winkler (1968) had The realization that raw sewage is rich in pathogenic shown that the inactivation of poliovirus 1 during viruses, and recent advances in laboratory techniques spraying was greatest at low humidities. (for instance, Lydholm and Nielsen 1980), have given Sorber, Schaub and Bausum (1974) developed a rise to many investigations into the effectiveness of theoretical model of the transmission of viruses in various treatment processes in reducing viral con- aerosols produced by spray irrigation with effluents centrations in sewage effluents. These studies have containing various enterovirus concentrations. The almost exclusively examined the removal of en- model indicates that a healthy young male working at teroviruses and coliphages, and these two groups of the wetted perimeter when strong effluent (6,000 viruses do not always behave in a similar way (nor may viruses per liter) is being sprayed may inhale as many they be good models for rotavirus or hepatitis A virus). as 240 viruses in 10 minutes; whereas if he is working Several reviews have been published (for instance Berg 200 meters from the wetted perimeter when weak 1973; Sproul 1976; WHO 1979). effluent (10 viruses per liter) is being sprayed, he may inhale only 0.0006 viruses in 10 minutes. These findings dependupon ssumpions mde abut clmatic By primary and seco7ndary sedimentation depend upon assumptions made about clitnatic conditions. The authors conclude that spray irrigation Primary sedimentation tanks, with retention times with chlorinated effluents from conventional treatment of 2-6 hours, allow a proportion of the viruses in the plants poses considerable risk of virus inhalation and sewage to adsorb onto solids and settle. Many viruses that better virus removal systems need to be applied will already be adsorbed to settleable solids in the prior to spray irrigation. influent. Removals reported in the literature, listed in Moore, Sagik and Sorber (1979) were able to isolate the appendixes of Feachem and others (1980), suggest small numbers of coliphages (up to 1.5 per cubic meter between 0 and 83 percent removal from influent to of air) and enteroviruses (up to 1.7 x 102 per cubic effluent. meter of air) from large volumes of air sampled 50 Rao and others (1977) recorded a 24 to 33 percent meters downwind of the wet-line edge of a wastewater removal of enteroviruses by primary settling tanks in spray irrigation site in California (USA). Teltsch and the wet season in Bombay. At other times of the year Katzenelson (1978) isolated echoviruses from 4 out of removal was between 41 and 83 percent with a 2-hour 12 air samples collected 40 meters downwind of retention time. Rao, Lakhe and Waghmare (1978) wastewater sprinklers in Israel. Bausum, Schaub and reported a 50 percent reduction of viruses in a pilot Kenyon (1978) studied a spray-irrigated golf course in plant settling tank at Nagpur (India). Sherman and Arizona (USA) and isolated seeded coliphage f2 from others (1975) and Naparstek and others (1976) studied aerosol droplets 563 meters downwind of sprinklers removal of seeded coliphage f2 in treatment plants in delivering secondary effluent and 137 meters dow- Maryland (USA) and found 35-47 percent average nwind of sprinklers delivering chlorinated effluent. removals in primary sedimentation tanks and 30 The possibility of virus transmission via aerosol percent removal during secondary sedimentation. One droplets will undoubtedly be the subject of a report suggests that factors other than settlement may considerable amount of research over the next few be operative in removing viruses from sedimentation years. Attention will focus upon risks to workers at tank effluent (Clarke and others 1961). sewage treatment facilities and at agricultural sites Similar performance may be expected from secon- employing spray irrigation with wastewater. A study dary sedimentation tanks, except that these are often from Israel (Katzenelson, Buium and Shuval 1976) designed with higher overflow rates. The sludge showed that the populations of kibbutzim that removed from sedimentation tanks will normally practiced spray irrigation with waste stabilization contain a 10-100 times higher concentration of pond effluent had a higher incidence of hepatitis A enteroviruses than the raw sewage. infection than kibbutzim in which no form of wastewater irrigation was used. However, it is most unlikely that transmission by aerosol droplets plays By storage any major part in the maintenance of endemic Storage is an effective method of virus inactivation, enteroviral infections in poor communities where basic especially at temperatures above 20'C. In any storage hygienic facilities are lacking. vessel, some sedimentation will also be taking place 152 ENVIRONMENTAL BIOLOGY & EPIDEMIOLOGY: VIRUSES that will remove a proportion of viruses to the sludge sludge treatment). The inactivation of enteroviruses, layer. Expected removal rates in stored sewage may both in sludge within the septic tank and in the be derived from the data given above on the survival of drainfield, will be considerably enhanced by warm enteroviruses in sewage (see also the appendixes of temperatures. Feachem and others 1980), although little is known about survival under tropical climatic conditions. Bv tricklingfilters By septic tanks The basic mechanism for virus removal by trickling filter plants is adsorption onto the biological slime, Removal of enteroviruses by septic tanks has been retention times are too brief for other processes to be very little studied, and not at all in developing significant. However, reported removal rates are low, countries. A septic tank is simply a settling chamber (or and this suggests that there is poor contact between chambers) with a mean retention time of 3 days or less. viruses and slime surface, that adsorbed viruses are In poorly designed tanks, or those requiring desludg- subsequently eluted by the flow of sewage passing ing, there is very considerable carryover of solids into through the filter, or both. the effluent. Viruses will be removed both by Sherman and others (1975) found that 9 percent and inactivation in the anaerobic liquor and by adsorption 19 percent of seeded coliphage 2 were removed by the to solids that settle to the sludge layer. Some studies of trickling filter beds in two treatment plants. When enterovirus removal have been conducted, and primary sedimentation trickling filters and secondary estimates may also be derived from information on sedimentation were considered together, coliphage survival in sewage and on removal by primary removals were 55 percent and 64 percent. Buras (1976) sedimentation (see the appendixes to Feachem and studied the performance of the Haifa (Israel) trickling others 1980). A series of laboratory experiments filter plant over a two year period. Average influent showed that a 99 percent reduction of poliovirus 1 in biochemical oxygen demand by the standard test septic tank effluent took 14 days at 20°C and 43 days at (ROD5) was 500 milligrams per liter, while average 7°C (Small Scale Waste Management Project 1978). effluent BOD5 was 70 milligrams per liter. The monthly Therefore, if all influent was held for 3 days at 20°C average enterovirus concentrations in the influent (because of short circuiting, it never is). a 64 percent varied between 6 x 103 per liter and 4.9 x 105 per liter, virus reduction might be expected. In practice, with a 2-year mean of the monthly means of 1.3 x 105 enterovirus reductions of 50 percent and under are to per liter. The monthly average concentrations in the be expected. Septic tanks usually serve small effluent varied between 3 x 103 per liter and 4.5 x I05 populations (5-200 people), and so influent and per liter, with a 2-year mean of the monthly means of effluent virus concentrations will fluctuate dramati- 9.6 x 104 per liter. An overall removal efficiency of cally. only 26 percent is derived. Kott, Ben-Ari and Vinokur The ultimate fate of viruses entering a septic tank (1978) isolated between 2.4 x 103 and 1.2 x 104 depends on the disposal of the effluent and the sludge. enteroviruses per liter of trickling filter plant effluent at Effluents are normally discharged to drainfields, where Haifa. viruses may be retained and inactivated in the soil. Clarke and Chang (1975) studied the performance of Cliver, Green and Bouma (1975) reported that septic bench-scale, rotary-tube trickling filters. At medium tank effluent (containing 109 seeded polioviruses per filtration rates poliovirus 1, echovirus 12, and liter) was rendered virus free after travelling 0.4 meters coxsackievirus A9 were reduced by 85, 83, and 94 through sand. with an application rate of 0.05 cubic percent, respectively. At higher filtration rates re- meters per square meter per day at 20°C. Higher movals were 59, 63, and 81 percent, respectively. The application rates or lower temperatures greatly authors failed to disassociate viruses from the reduced virus removal. This and other studies relevant biological slime in the filters and concluded that either to enterovirus removal from septic tank effluent have the slime-virus complex is very stable or that the virus been recently reviewed in detail (Small Scale Waste is somehow inactivated by adsorption to the slime. Management Project 1978). More information on Fecal coliform and fecal streptococci removal rates virus removal by sand and soil is given in the closely paralleled those for enteroviruses and lead the subsections below on filtration and land treatment. authors to suggest that these bacteria may be used as Septic tank sludge will be rich in accumulated indexes of viral removal by trickling filters. Gerba, enteroviruses and requires treatment by digestion, Stagg and Abadie (1978) investigated the association drying or composting (see the subsections below on with solids of enteroviruses in the effluent of a trickling ENTEROVIRUSES, POLIOMYELITIS, AND SIMILAR INFECTIONS 153 filter plant in Houston (Texas, USA). Between 9 and Since retention times in activated sludge plants are 196 enteroviruses per liter were contained in the short (typically 6-12 hours), it is to be expected that effluent, and between 3 and 20 percent of these were most removal of virus is by adsorption to flocs that are adsorbed onto solids. This is a much lower solids- subsequently removed by sedimentation. Glass and associated proportion than that reported by the same O'Brien (1980) calculated that the inactivation rate of authors for activated sludge effluent (49 to 100 percent) enteroviruses in activated sludge mixed liquor at 25°C and supports the contention that the poor virus was about 12 percent per hour. Therefore, in an removal efficiency of trickling filters is due to the activated sludge tank with a mean retention of 9 hours, system's providing insufficient opportunity for virus only 68 percent virus removal would be obtained by adsorption to solids or slime. inactivation even if all liquor were retained for the Few data are reported on the removal of mean retention time. enteroviruses by trickling filters in developing count- Moore and others (1974) studied a contact ries. Nupen (1970) reported that the trickling filter stabilization plant (contact time of 20-30 minutes plant (together with primary and secondary sedimen- followed by a 4-hour stabilization period) near Austin tation) at Windhoek (Namibia) reduced an influent (Texas, USA). Incoming enterovirus concentrations concentration of 2 x 104 viruses per liter by 82 percent. were 250-1,500 per liter. Between 80 and 90 percent of In a subsequent report (Nupen, Bateman and enteroviruses became solids associated in the mixed McKenny 1974) it was stated that the outflow from the liquor, and overall removal varied from 80 to 90 primary sedimentation tanks at Windhoek contained percent. In subsequent laboratory studies it was found 7 x 104 viruses per liter and that, following trickling that 99 percent of poliovirus in mixed liquor became filtration and secondary sedimentation, this was solids associated after 1 hour's aeration. The same reduced by 70 percent in winter and by 95 percent in authors (Malina and others 1974) also reported summer. laboratory model studies on seeded poliovirus removal Removal rates reported in the literature listed in the by activated sludge and contact stabilization processes. appendixes of Feachem and others (1980) vary Poliovirus removals by the activated sludge model between 0 and 95 percent. It is not always clear from were 92-99.9 percent and were not especially sensitive the literature whether removal in the trickling filter to changes in aeration time (range of 5-15 hours) or to alone, or across the whole treatment plant, are being mixed liquor suspended solids concentration (range of recorded. Predictably, removal achieved in laboratory 1940-2710 milligrams per liter). Poliovirus removal models (for instance Clarke and Chang 1975) is far was also not affected by whether pure oxygen or higher than that achieved in practice (for instance, compressed air was used. Contact stabilization Buras 1976), and removal is reduced at higher loading (contact time of 16-32 minutes followed by 2.1 hours rates. A typical removal rate for a trickling filter unit stabilization period) removed 84-99.8 percent of alone might be 5 to 20 percent, whereas a complete poliovirus. Sludges, from both the activated sludge and trickling filter plant (with no tertiary processes) could contact stabilization models, contained between 70 be expected to remove 25-60 percent of enteroviruses. and 5,800 enteroviruses per gram. Many of the viruses removed from the sewage will be Balluz, Jones and Butler (1977) studied a concentrated into the primary and secondary sludges. laboratory-scale activated sludge plant that received raw settled sewage from Guildford (UK) with a mean BOD5 of 270 milligrams per liter and produced an By activated sludge effluent with a mean BOD5 of 11 milligrams per liter. The temperature was 15°C. An average poliovirus The most significant variables in the removal of removal of 99.8 percent was recorded, with 85 percent enteroviruses from activated sludge effluent are of virus associated with the solids fraction of the mixed temperature, retention time (Heyward and others liquor. The authors stress that the efficiency of the 1977; Malina and others 1975), the degree of plant in removing viruses may be closely related to the adsorption of viruses onto activated sludge flocs ability to remove suspended solids and that the (which may vary considerably between different virus subsequent treatment of the virus-rich sludge is of the types-Farrah and others 1978; Gerba and others utmost importance. In similar experiments with 1980), and the efficiency of removal of suspended solids coliphage f2, the same authors (Balluz, Butler and from the final effluent. Studies on virus removal by Jones 1978) found a removal of only 68 percent and activated sludge are listed in the appendixes of that a mere 16 percent of phage was associated with the Feachem and others (1980). solids fraction. It was concluded that coliphage is an 154 ENVIRONMENTAL BIOLOGY & EPIDEMIOLOGY: VIRUSES unsuitable indicator of enterovirus behavior in sewage removed from the sewage will be concentrated into the treatment processes (see also Butler and Balluz 1979). primary and secondary sludges. These findings on coliphage in activated sludge are important in interpreting the results of studies in which dih coliphage has been seeded into treatment plants to By oxidation itc study virus removal. Naparstek and others (1976) Practically no information is available on en- recorded the removal of seeded coliphage f2 at an terovirus removal by oxidation ditches (see the activated sludge plant in Maryland (USA). On appendixes of Feachem and others 1980). The process average, only 11 percent of coliphage was removed by is essentially similar to activated sludge, but the longer the aeration tanks and secondary sedimentation units, hydraulic retention times (1-3 days), and the higher and the removal across the whole plant (which proportion of sludge recycling giving a solids retention included chlorination) was only 80 percent. Safferman time of 10-30 days, are features that should produce and Morris (1976) studied the coliphage removal improved virus removal. This is supported by ability of a sophisticated pilot plant that incorporated laboratory studies in the USSR indicating the high-rate activated sludge, clarification, nitrification, elimination of seeded enteroviruses following 2 day's denitrification, aeration, and filtration. Average flow aeration (Goncharuk and others 1970) and by pilot- was 200 cubic meters per day, and the final effluent had plant studies in India showing 97-99.7 percent a BOD5 of 2 milligrams per liter. Removal of coliphage reduction of naturally occurring enteroviruses (Rao by the high-rate activated sludge unit was between 90 and others 1973). However, full-scale ditches will and 99 percent, whereas removal across the whole achieve considerably lower removal rates, and poorly plant averaged 99.97 percent. operating plants will most likely remove a negligible Gerba, Stagg and Abadie (1978) found between 0.1 proportion of enteroviruses. and 7 enteroviruses per liter in the effluents from two activated sludge plants in Houston (Texas, USA). Between 49 and 100 percent of viruses in the effluent B' waste stabilization ponds were adsorbed onto solids. Fujioka and Loh (1978) Very few systematically compiled data exist on the investigated a treatment plant in Hawaii (USA) that virus removal properties of well-constructed waste employed settling and activated sludge. Influent stabilization pond systems in warm climates. Removal contained 27-19,000 viruses per liter, while effluent rates reported (see the appendixes of Feachem and contained 7-5,222 per liter. Rao and others (1977) others 1980), vary widely, which is partly due to poor studied virus removal at the Dadar sewage treatment pond design, poor experimental procedures and short- plant (Bombay, India) where about 19,000 cubic circuiting of sewage flow across the ponds (Malherbe meters of sewage per day are treated by activated and Strickland-Cholmley 1967). sludge prior to marine discharge. Effluent BOD5 over a Rao, Lakhe and Waghmare (1978) reported that 2-year period averaged 6 milligrams per liter (98.5 even very poorly designed stabilization ponds in India percent reduction), and effluent suspended solids achieved virus removal rates similar to those of averaged 20 milligrams per liter (97.2 percent activated sludge plants. A single pond with 3-10 days reduction). Raw sewage contained 250-1,250 en- retention removed 89.9-96.2 percent of viruses; a teroviruses per liter, and final effluent contained 5-60 single pond with a 2.7 days retention time removed per liter. Removal rates were between 90 and 99 94.8-97.3 percent, and 4 ponds in series with a 17.2 percent. days retention time removed 88-98.9 percent of Both laboratory and field experience indicate that viruses. activated sludge systems are not particularly effective There is ample evidence of reduced survival of in removing enteroviruses but are more effective than enteroviruses in stabilization ponds at warm summer trickling filters (see above and Heyward and others temperatures when compared with the same ponds at 1977). Enterovirus removal in activated sludge cooler winter temperatures (Funderberg and others treatment works is in the range 0 to 99 percent, 1978; Kott, Ben-Ari and Betzer 1978; Lefler and Kott although better results (up to 99.9 percent) have been 1975; Slanetz and others 1970). Viruses adsorbed to achieved in laboratory and pilot-scale models. It is settleable solids will fall to the sludge layer at the base reasonable to assume that a well-run activated sludge of the facultative pond where they may survive for plant may reduce the enterovirus concentration by extended periods (Funderberg and others 1978). Other 50-95 percent, but that a poorly operated plant will biological and physical factors-such as a virucidal achieve negligible removal. Many of the viruses increase in pH to 9 or above caused in part by blooms ENTEROVIRUSES, POLIOMYELITIS, AND SIMILAR INFECTIONS 155 of algae (Funderberg and others 1978)-also may (1 8-20°C), with initial concentrations of 2,000 per liter, determine virus survival. inactivation was complete within 11-35 days. Nupen Lund (1979) estimated that virus inactivation in (1970) and Nupen, Bateman and McKenny (1974) heavily polluted water might proceed at approximately reported a 95 percent reduction in enteroviruses in a I log unit in 5 days at 32°C and I log unit in I day at chain of 9 maturation lagoons (total retention time 14 35°C. Funderberg and others (1978) reported polio- days) receiving the trickling filter plant effluent at virus removal in model outdoor ponds near Austin Windhoek (Namibia). Lagoon effluent contained up to (Texas, USA). During the summer over 99 percent of 25 enteroviruses per liter in summer and up to 842 per added virus was lost within 5 days, whereas this degree liter in winter. of removal took 15 and 25 days in spring and winter, respectively. COAGULATION. Coagulation is one of the more These data suggest that well-designed stabilization cheGULaT Coagulation isoone ofrthe more ponds in the tropics (with minimal short-circuiting, efete hem procse fo removing viruses from water temperature above 25°C, and overall retention wastewater. Alum [A12(S04)33, lime [Ca(OH)2], iron watr t r a e 2, asalts, and polyelectrolytes have all been used. Wolf and time of 30 days or more) should achieve very high levels others (1974) reported a greater than 99.6 percent of virus removal (at least a 4 log reduction). removal of seeded coliphage f2 and poliovirus 1 in a Confirmation of this must await further experimen- laboratory model coagulation-sedimentation system tation on well-designed waste stabilization ponds in employing alum. Lime is probably the most effective coagulant, since the high pH values produced are strongly virucidal (particularly above pH 11-see, for By aerated lagoons example, Nupen, Bateman and McKenny 1974). For An aerated lagoon on its own may be expected to maximum efficiency, coagulation should be followed have a virus removal rate similar to, or a little better by slow sand filtration (Berg 1973; Berg, Dean and ' . . ~~Dahling 1968; Derbyshire and Brown 1979; Grabow, than, an oxidation ditch. If the effluent is treated in Midn and Dbssone1978 Nupen 1970; Shelton maturation ponds, removal rates as in waste andDre 193 spou1978 Nupe197)0. Shelton stabilization ponds are expected. No specific data are reviewro virus Sreol by c onrandipH available, but warm temperatures will certainly revaew of vnrus removal by coagulation and pH increase enterovirus inactivation rates. The sludge adjustments has been recently published (Sproul 1980). drawn off from secondary sedimentation tanks or settling ponds will be rich in enteroviruses. FILTRATION. Sand filters can remove a high proportion of viruses from secondary effluents, but By tertiary treatment reported performances are erratic. Higher removal rates are achieved at lower filtration rates. Removal of Some tertiary, or advanced physicochemical, treat- viruses is also cnhanced by low or high pH and by the ment processes are effective in removing viruses. presence of cations (Jenkins and others 1980) and very However, they add cost to sewage treatment and in much enhanced by coagulation prior to filtration (Berg some cases are too technically and mechanically 1973). sophisticated to be appropriate in developing count- Sproul (1976) reported 99.7 percent removal from ries. activated sludge effluent at a filtration rate of 0.04 cubic meters per square meter per day and 100 percent LAGOONING. Secondary effluents may be further removal at 0.007 cubic meters per square meter per treated in maturation lagoons. Enterovirus removal day. Safferman and Morris (1976) reported very poor rates and processes are the same as in waste removal of coliphage (0 to 48 percent) by dual and stabilization ponds, except that little or no sedimen- multimedia filters without precoagulation. Berg, Dean tation takes place. High rates of virus removal can be and Dahling (1968) recorded an 82-99.8 percent achieved if several lagoons are employed and short- removal of viruses in lime coagulated effluent at a circuiting is avoided. filtration rate of 131 cubic meters per square meter per Kott, Ben-Ari and Betzer (1978) investigated the use day. of lagoons for the tertiary treatment of trickling filter Very significantly from the viewpoint of developing effluent at Haifa (Israel). In winter (temperatures down country operating problems, Vaughn and others to 8°C), initial enterovirus concentrations of 1.1 x 104 (1978) stated that the treatment plant at Holbrook per liter were reduced to zero in 47-73 days. In summer (New York, USA), which features extended aeration, 156 ENVIRONMENTAL BIOLOGY & EPIDEMIOLOGY: VIRUSES denitrification, and gravity sand filtration, was combined chlorine added to primary effluent in- experiencing "operating difficulties" and they isolated activated only between 1 and 2 log units of enterovirus up to 283 enteroviruses per liter from the final effluent. in 15 minutes, whereas in the same experiments fecal Assuming a raw influent concentration of about 1,000 coliform reductions ranged from 3 to more than 5 log per liter, a removal rate of only 72 percent was achieved units, and total coliform reductions ranged from 5 to in filtered tertiary effluent in an industrialized country. more than 7 log units. Similarly, Rao, Lakhe and Waghmare (1978) reported Different species of human excreted virus have that a sewage reclamation plant at a factory in Bombay different sensitivities to inactivation by chlorine. incorporated extended aeration, alum coagulation, Reoviruses are among the most sensitive, and rapid sand filtration, and deionization but achieved a polioviruses are among the most resistant (Drulak, virus removal of only 81-99 percent. These are Wallbank and Lebtag 1979; Englebrecht and others powerful illustrations both of the operating difficulties 1978; Shuval and others 1966: Sproul 1976). frequently experienced with advanced wastewater Boardman and Sproul (1977) studied the in- treatment plants even in developed countries and of the activation of coliphage T7 by chlorine when the phage inapplicability of much virus removal data obtained in was adsorbed to particles of clay, aluminium oxide, or laboratory or pilot-scale plants to full-scale operating calcium carbonate in water. It was concluded that treatment plants. adsorption of virus to the surface of inorganic particles offered no protection against inactivation by chlorine, DISINFECTION. Enterovirus removal from secon- but that encapsulation by a particle may afford dary or tertiary effluents by disinfection has been the protection. This conclusion has been confirmed by subject of numerous investigations in recent years. The studies by Hejkat and others (1979) into the most widely used disinfection technique for sewage inactivation by chlorine of poliovirus in fecal effluents is chlorination, and there is considerable homogenates.Theyfoundthatthevirusthatwasclosely evidence that viruses are less readily destroyed by associated with, or occluded within, small fecal effluent chlorination than enteric bacteria (Berg and particulates was protected from chlorine inactivation. Metcalf 1978; Snead and others 1980), although, A combined chlorine residual of 6.6 milligrams per liter unlike some bacteria, viruses cannot regrow in the (at pH 8 and 220C) achieved a 50 percent inactivation effluent subsequently. of solids-associated virus in 15 minutes, whereas only As with the bactericidal effects of chlorine in water 1.4 milligrams per liter of combined chlorine were treatment, free chlorine (especially in the form of sufficient to obtain the same reduction of free virus in hypochlorous acid at low pH and particularly at warm the same time. However, these differences were small temperatures) is a far more potent virucide than compared with differences in inactivation due to combined chlorine (monochloramine, dichloramine, dissolved organics that determined whether any free and other compounds), which is formed in the presence chlorine, as opposed to combined chlorine, was of ammonia and organic matter (Olivieri, Donovan present. Stagg and others (1978) studied three and Kawata 1971). Chlorine added to most sewage treatment plants in Houston (Texas, USA) and found plant effluents is rapidly converted to combined that between 2 and 21 percent of coliphages in plant chlorine, and this, together with the protective effect of effluent prior to chlorination were solids associated. virus association with solid particles, may result in very Passage through chlorine contact chambers in- poor virus removal. activated freely suspended phages to a greater extent In clean water at pH 7-8 1-2 milligrams per liter of than solids-associated phages, and increased the free chlorine maintained for 1-2 hours will be more proportion of solids-associated phages in the final than sufficient for complete virus inactivation. effluent to between 6 and over 99 percent. Only about Englebrecht and others (1978) showed that 6 different 15 percent of the solids-associated viruses were enteroviruses in water were all inactivated by 99 embedded; the remainder were adsorbed. percent in under 5 minutes when 0.5 milligrams per It is clear from the above that the efficacy of effluent liter of free chlorine were applied at 5C and pH 7-8. In chlorination in virus removal depends considerably a secondary sewage effluent (BOD5 of 45 milligrams per upon the quality of the effluent prior to chlorination. liter), however, poliovirus was reduced by 50 and 90 The better the quality of the effluent, the higher the percent in 6 hours after applying 5 and 11 milligrams virus inactivation attained by a given chlorination per liter of chlorine, respectively (Shuval and others system; tertiary treatment (for instance, by filtration) is 1966). Similarly, Berg and Metcalf (1978) reported therefore often recommended to reduce further that, at 22-240C, 11-23 milligrams per liter of suspended solids and dissolved organics prior to ENTEROVIRUSES, POLIOMYELITIS, AND SIMILAR INFECTIONS 157 chlorination (Dryden, Chen and Selna 1979; Bausum, Schaub and Kenyon (1978) found that Kirkpatrick and Presecan 1978). chlorination of a trickling filter effluent in Arizona Several reports indicate that well-run chlorination (USA) reduced the concentration of seeded coliphage units, receiving high quality effluents, can produce a by only 95 percent, as compared with a bacterial virus-free final effluent. Kott, Ben-Ari and Betzer reduction of 99.97 percent. Kott and others (1974) (1978) investigated the effect on enteroviruses of studied chlorinated waste stabilization pond effluents chlorinating a trickling filter effluent at Haifa (Israel). in Israel (8 milligrams per liter of applied chlorine for 1 At a chlorine dose of 20 milligrams per liter and a hour at 20°C) and found an average enterovirus contact time of 2 hours, enterovirus concentrations reduction of only about 10 percent, whereas the total were reduced from up to 5,900 per liter to zero (see also coliform reductions were 2 log to > 6 log units. The Kott, Ben-Ari and Vinokur 1978; Lindeman and Kott chlorinated pond effluents contained between 300 and 1971). 1,000 enteroviruses per liter. Other experiments found The possibility of a virus-free chlorinated effluent is that, at pH 6.0 with a 2-hour contact time, seeded also illustrated by data from some of the advanced poliovirus 1 in stabilization pond effluent was reduced wastewater reclamation plants. Culp (1974a, 1974b) by 86 percent with 20 milligrams per liter of applied reports complete virus inactivation at a Lake Tahoe chlorine, by 87 percent with 40 milligrams per liter of (USA) sewage treatment plant by carefully controlled chlorine, and by 100 percent with 60 milligrams per chlorination. Grabow and Isaacson (1978) failed to liter of chlorine. isolate any enteroviruses from 144 10-liter samples of The chlorination of inadequately treated sewage, in water produced by the advanced wastewater re- the hope of thereby removing much of the microbial clamation plants at Windhoek (Namibia) and Pretoria hazard, is disturbingly widespread despite clear (South Africa). These plants incorporated a train of evidence that it is generally ineffective and represents advanced processes and included break-point chlori- bad engineering practice. The authors of this book nation sufficient to produce 0.2-0.6 milligrams per liter have observed this practice on several occasions, and of free residual chlorine after 2-3 hours of contact time have frequently heard it recommended in developing (Nupen 1970; Nupen, Bateman and McKenny 1974). countries when concern is being expressed about the However, chlorination in no way guarantees a virus- discharge of highly polluted effluents from improperly free effluent. Sherman and others (1975) found that the designed or malfunctioning sewage treatment plants. chlorination of trickling filter plant effluents from two An interesting case study of this problem is the treatment plants in Maryland (USA) reduced seeded investigations by Sattar and Westwood (1978) in coliphage by 60 percent. Overall reductions of phage Ottawa (Canada), a city of 500,000 people that across the two plants were 82 percent and 86 percent. discharged 90 percent of its sewage into the Ottawa Fujioka and Loh (1978) reported isolating 25-34 and River after the wastes received only primary treatment 2-750 enteroviruses per liter from the chlorinated (sedimentation) and chlorination. Two treatment effluent of two treatment plants in Hawaii (USA). plants were studied that received a raw sewage with a Influent concentrations were 5-268 and 27-19,000 1oD5 of 79-98 milligrams per liter and that produced a enteroviruses per liter, respectively. Wellings and chlorinated primary effluent with a ROD5 of 44-48 others (1975) found on average 0.13 enteroviruses per milligrams per liter. Raw sewage samples were 80 liter (53 percent of samples positive) in the chlorinated percent positive for enteroviruses, with an average effluent from a package treatment plant receiving concentration of 1,000 per liter. Samples of sedimen- sewage containing 161 viruses per liter from a mobile tation tank effluent were 72 percent positive for home park. Wellings, Lewis and Mountain (1974, enteroviruses and also contained 1,000 viruses per liter. 1976) isolated up to 12 and 98 enteroviruses per liter, in Samples of final chlorinated effluent were 56 percent two studies on the chlorinated effluent from an positive for enteroviruses and contained 27 viruses per activated sludge plant in St. Petersburg (Florida, liter. The Ottawa River is used for recreation and USA). Metcalf, Wallis and Melnick (1974) isolated up provides the raw water source for about 600,000 to 4 enteroviruses per liter from a chlorinated effluent people. (1.2-1.9 milligrams per liter of residual chlorine after Various other wastewater disinfection systems have 10 minutes of contact) at an activated sludge plant near been studied with respect to their ability to inactivate Houston (Texas, USA). Vaughn and others (1978) viruses. Ozone is a very potent virucide, and its activity isolated up to 26 and 98 viruses per liter from the is less disturbed by organic pollution than is the case chlorinated secondary effluents from two sewage for chlorinc (De Michele 1974; Dryden, Chen and treatment plants on Long Island (New York, USA). Selna 1979; Evison 1978; Katzenelson and 158 ENVIRONMENTAL BIOLOGY & EPIDEMIOLOGY: VIRUSES Biedermann 1976; Munger, Heyward and Swartz percent of poliovirus in primary effluent was removed 1977; Pavoni and Tittlebaum 1974; Rakness and Hegg in the top 0.2 meters of loamy sand, and no poliovirus 1979; Sproul 1976). Bromine chloride and paracetic was detected below 0.8 meters, when the flow rate was acid have been evaluated and are also little affected by approximately 0.2 cubic meters per square meter per organic matter in the effluent (Hajenian and Butler day. In other experiments it was shown that poliovirus 1980). Chlorine dioxide also effectively inactivates adsorption by loamy sand is reduced when the flow enteroviruses in water at a rate similar to hypochlorous rate is increased above some critical value, whereas acid. Unlike hypochlorous acid, chlorine dioxide is flow rate changes above and below this value do not more potent at higher pH values (Cronier, Scarpino affect adsorption. The critical value for loamy sand was and Zink 1978). Radiation at a level of 3-5 kilogray6 about 1 cubic meter per square meter per day; below inactivates approximately 90 percent of viruses in this flow rate poliovirus penetration was less than 1.6 sewage effluent, whereas only 1-1.5 kilogray are meters, whereas above it viruses penetrated the entire required to achieve the same inactivation of viruses in 2.5-meter column. distilled water (Metcalf 1977; Sullivan and others Duboise, Moore and Sagik (1976) reported that 1971). Photodynamic oxidation has also been eva- poliovirus and coliphage adsorbed to cores of loamy luated for the disinfection of wastewaters (Gerba, sand were eluted less by intermittent application of Wallis and Melnick 1977a, 1977b). However, all these effluent or water than by continuous application. In techniques are currently at the experimental stage; in addition, the chemical quality of the effluent improved any case, they may involve a level of technical more by soil filtration when the effluent was applied sophistication and cost that would make them intermittently than when it was applied continuously inappropriate in many situations in developing (see also Duboise and others 1974). countries. Bitton, Masterton and Gifford (1976) found that under experimental conditions coliphage T2 and LAND TREATMENT. Land treatment by soil filtration poliovirus were adsorbed more readily when suspen- or groundwater recharge can be highly effective in ded in tap water than in secondary effluent, and that removing viruses from primary or secondary sewage effluent is a more potent eluent than tap water for effluents, but results reported in the literature vary washing adsorbed viruses out of soil columns. Lefler widely. and Kott (1976) also found higher elution of poliovirus Lance, Gerba and Melnick (1976) showed, in and coliphage from sand with effluent as compared laboratory studies, that poliovirus in secondary with tap water. However, Duboise, Moore and Sagik effluent was almost completely removed by filtration (1976) reported that flooding cores of loamy sand with through loamy sand after flowing to a depth of 1.6 dechlorinated effluent eluted fewer polioviruses than meters and was reduced by 99 percent after 0.4 meters when distilled water was used. of flow. These results were obtained at filtration rates of Landry and others (1979) found that 72-100 percent both 0.55 cubic meters per square meter per day and of polioviruses, coxsackieviruses, and echoviruses were 0.15 cubic meters per square meter per day. Flooding retained when tertiary sewage effluent was passed the soil with deionized water (to simulate a rainstorm) through 1.25-meter natural cores of gravelly sand at a caused some downward movement of the viruses. but rate of 20 cubic meters per square meter per day. this was greatly reduced when CaC12 was added to the Flooding the cores with artificial rain water released deionized water. Drying of the soil between effluent 0-67 percent of the adsorbed viruses, whereas flooding application and a simulated rainstorm considerably with sewage effluent released 0-14 percent. A total of reduced desorption of viruses; 5 days drying prevented eight laboratory and field strains of enteroviruses were subsequent desorption completely. The authors used in these experiments. Some differences in concluded that viruses would move through 2.5 meters adsorption among the strains were recorded (with of calcareous sand only if heavy rains fell within a day echovirus 1 showing the greatest soil affinity), and the following the cessation of sewage application. In proportion of adsorbed viruses being eluted by follow-up studies (Gerba and Lance 1978; Lance and rainwater or sewagediffered markedly (with echovirus 1 Gerba 1980; Lance, Rice and Gilbert 1980), similar being the least mobilized and a wild strain of poliovirus adsorption and elution results were obtained in loamy 3 being the most readily eluted). The authors concluded sand whether polioviruses were suspended in primary that soil adsorption-elution behavior is strain de- or secondary effluent. In one series of experiments, 99 pendent and warn against the application of laboratory data from experiments using only a single strain of 6. See footnote 5, above. poliovirus 1. Gerba and others (1980), Goyal and Gerba ENTEROVIRUSES, POLIOMYELITIS. AND SIMILAR INFECTIONS 159 (1979), and Goyal and Melnick (1978) also reported and around the dome. Enteroviruses were isolated from wide intertypic and intratypic variation in adsorptive 3 out of 48 well-water samples, and horizontal behavior among enteroviruses in various soils. mnovement of viruses through the saturated soils of at Burge and Enkiri (1978a) reported substantial least 7 meters was demonstrated. differences in the ability of five soils to adsorb Gilbert and others (1976a, 1976b) studied virus coliphage viruses. More acidic soils had higher removal from activated sludge effluent (up to 75 viruses adsorption rates, and one loamy sand adsorbed no per liter) applied to loamy sand (infiltration rate of 0.27 viruses (see also Burge and Enkiri 1978b; Vilker and cubic meters per square meter per day) at a 7-year-old Burge 1980). Similarly, Lefler and Kott (1974b) found wastewater renovation plant near Phoenix (Arizona, that many coliphage f2 and poliovirus 1 were able to USA).Novirusesweredetectedintheobservationwells, pass through a 0.2-meter sand column (at an indicating at least a 99.99 percent removal after flow application rate of 1.7 cubic meters per square meter through 3-9 meters of soil. In contrast, Schaub and per day) and that only a high concentration of bivalent Sorber (1977) reported very low viral removal by soil cations (Ca' + and Mg' +) prevented this. Funderberg filtration (infiltration rate 0.07 cubic meters per square and others (1979), Goyal and Gerba (1979), and meter per day) of primary effluent at a 30-year-old Moore and others (1979) have also reported wide treatment plant in Massachusetts (USA). The soil was variation in virus adsorption behavior dependent on unconsolidated silty sand and gravel. Seeded coliphage soil properties. f2 viruses were reduced by an average of 53 percent after Studies by Scheuerman and others (1979) showed 18 meters of percolation, and seeded f2 and indigenous that some organic soils have poor virus adsorption enteroviruses were sporadically detected in the potential due to the presence of water-soluble humic groundwater at horizontal distances of 180 meters from substances (humic and fulvic acids), which may the application zone. compete with viruses for adsorption sites on soil It is clear from these and other studies that particles or may react with certain surface groups on adsorption to soil particles, rather than viral death, is virus particles that are functionally important in the dominant removal mechanism. Adsorption is adsorption to soil. increased by low infiltration rates (say <0.1 cubic Wellings, Lewis and Mountain (1974) studied an meters per square meter per day), by low pH, and by effluent spray irrigation site near St. Petersburg the presence of divalent cations (Ca++ and Mg +). (Florida, USA). The effluent from the activated sludge Adsorption is reduced in the presence of soluble plant contained up to 240 enteroviruses per liter, and organic matter which competes for adsorption sites on the final chlorinated effluent contained up to 98 per the soil particles. Adsorption and elution behavior liter. The effluent was applied to a sandy soil at between depend very much upon the characteristics of the soil 0.007 and 0.04 cubic meters per square meter per day. and the particular strain of virus. A great deal of further Water collected in drains 1.5 meters under the soil experimentation will be required before the optimal contained polioviruses, echoviruses, and reoviruses soil structures-and their relationships to infiltration (2 out of 9 samples positive). Enteroviruses were also rates, application schedules, and virus removal isolated from wells 3 and 6 meters deep at the site performance-are fully understood. It is already following heavy rain. apparent, however, that by passing even raw sewage Wellings and others (1975) studied the discharge of through less than 1 meter of a suitable soil it is possible effluent from a 154-unit mobile home park into a to reduce the virus concentration by as much as, or more cypress dome in the wetlands of Florida (USA). The than, that normally achieved by wastewater chlori- population of the park varied between 310 and 337 nation (Gerba 1979). Because of higher temperatures during the study and produced a raw sewage with an there, the effectiveness of land application in virus average of 161 enteroviruses per liter (range between 0 removal in the developing countries is likely to be and more than 700 per liter). Polioviruses 1, 2, and 3 greater than that generally reported from temperate accounted for 40 percent of isolates identified, with areas. It must be remembered, however, that without coxsackieviruses (B3 and B4) making up 43 percent, efficient management, operation, and maintenance and echoviruses (7, 11, and 14) the remaining 17 land application systems will become insanitary bogs. percent. Chlorinated effluent from a package treatment The above discussion has dealt exclusively with soil plant yielded polioviruses and coxsackieviruses in 8 filtration and groundwater recharge as methods of out of 15 samples taken. The effluent was discharged land treatment for wastewaters. The other major type into the cypress dome, and groundwater quality was of land treatment technology is the grass plot or monitored in 18 3-meter-deep wells constructed in overland run-off method. In these systems a significant 160 ENVIRONMENTAL BIOLOGY & EPIDEMIOLOGY: VIRUSES proportion of the effluent may run over the surface of Even less is known about the virological aspects of the soil and not flow through it, and it may be expected night soil and night soil treatment. that virus removal will be poor compared with the soil filtration data reported above. Experiments by Schaub and others (1980) confirmed this, showing a removal of B' pit latrines only 30-60 percent of seeded f2 bacteriophage and Little information is available, but it is probable that only 76-88 percent of indigenous excreted virus during enteroviruses survive for several weeks in pit latrines treatment on 36 meter long grass plots with a 3 percent (see the sections above on occurrence and survival in slope. feces and night soil and in sludge; see also the appendixes to Feachem and others 1980). In warm OTHER PROCESSES. A variety of other treatment climates, the pit contents should be free of en- processes are associated with advanced wastewater teroviruses if they are left for at least 3 months before treatment plants and with water reclamation or digging out. renovation projects. Some of these processes have been A pit latrine may act as a source of viral groundwater assessed for virus removal capability. Carbon adsor- pollution depending on the type of soil, groundwater ption and nitrification do not seem particularly levels, and the proximity of local wells (see the sections effective, whereas denitrification was reported to above on occurrence and survival in groundwater and remove 97 percent of coliphage (Berg 1973; Gerba and on virus removal by land treatment). others 1974; Safferman and Morris 1976; Sproul 1976). Francis, Brown and Ainslie (1953) isolated po- Complete water reclamation plants, incorporating a lioviruses (16 out of 220 samples positive) and train of advanced processes, are generally reported to coxsackieviruses (10 out of 63 samples positive) from achieve total virus removal when operating pit latrines in poor areas of four towns in southern perfectly. The Lake Tahoe (Nevada, USA) recla- Texas (USA). Pit latrines with polioviruses were not mation plant has occasionally let through viruses associated with known cases of poliomyelitis, an beyond the carbon adsorption stage, but they were epidemic of which was taking place at the time eliminated by chlorination (Berg 1973). Similarly, the (March-July of 1948), but were associated with the Windhoek (Namibia) reclamation plant is reported to isolation of polioviruses from flies in the vicinity. have achieved a virus-free effluent, despite an influent virus concentration of up to 2 x t04 per liter (Grabow and Isaacson 1978; Nupen 1970; Stander and Clayton B anaerobic digestion 1977). Although some form of anaerobic digestion is used to treat sludge from most larger sewage treatment plants, very little information is available on the virus removal performance of full-scale digesters. (Some Inactivation by Night soil and Sludge laboratory studies are discussed below and arc listed in Treatment Processes the appendixes of Feachem and others 1980). Ward and Ashley (1976) investigated the in- activation rate of poliovirus in digested sludge and Raw night soil contains all the viruses being excreted found that it was greater than 1 log unit per day at by the contributing population. Sewage works sludges 28°C and about 1 log unit per 5 days at 4°C. They are rich in viruses because a high proportion of viruses concluded that anaerobically digested sludge contains in sewage are, or become, solids-associated and are a specific virucidal agent; in a subsequent study (Ward therefore concentrated into both primary and secon- and Ashley 1977a) they identified this agent as dary sludges (Lund 1973; Lund 1976; Lund and Ronne ammonia (see also Fenters and others 1979). Ammonia 1973; Wellings, Lewis and Mountain 1976). Interest in is not virucidal in its charged state, but free ammonia, viruses in sludges has been stimulated by the fact that a which is formed at pH values of 8 and above, is highly large proportion of sewage sludge is applied to the land virucidal to enteroviruses but much less so to as a method of disposal and soil enrichment. reoviruses. Ward and Ashley concluded that ammonia Information on this subject is restricted to acts as a potent enterovirucide in raw and digested laboratory studies and a few field studies conducted in sludges with high pH values. At pH 9.5 and 21°C, North America and Europe. Little is known about greater than 3 log unit and 5 log reductions in viruses in sludge in developing countries or about poliovirus concentrations were obtained in 72 hours in sludge treatment under tropical climatic conditions. raw and digested sludges, respectively. A later study ENTEROVIRUSES. POLIOMYELITIS, AND SIMILAR INFECTIONS 161 confirmed that reovirus 3 was unaffected by the and centrifuged at a Houston (Texas, USA) treatment presence of ammonia (Ward and Ashley 1977c). plant. Eisenhardt, Lund and Nissen (1977) studied the Investigators who have looked for viruses in digested inactivation of coxsackievirus B3 in a laboratory-scale sludge have generally found them in considerable anaerobic sludge digester at pH 7. At 32°C a 5 log numbers (Berg and Metcalf 1978; Grigoryeva, reduction in virus concentration occurred in about 14 Korchak and Bey 1969; Hurst and others 1978; Sattar days, whereas at 35°C the same reduction took only 4 and Westwood 1979; Wellings, Lewis and Mountain days. Inactivation was slightly faster when the virus 1976). Some laboratory studies have reported an was held in pasteurized sludge. Bertucci and others inactivation rate of around 1 log unit per day at (1977) ran a laboratory anaerobic digester (pH 30-35°C (for instance, Eisenhardt, Lund and Nissen 7.2-7.4) at 35°C and compared inactivation rates of 1977; Fenters and others 1979; Ward and Ashley various enteroviruses. Inactivation rates varied from 1976). At this rate of inactivation, typical anaerobic 75 percent per day for echovirus 11 to 97 percent per digestion at 35°C for 35 days should produce a virus- day for coxsackievirus A9. free sludge with a wide margin of safety. However, Sanders and her coworkers (1979) pointed out that Sanders and others (1979) have shown that in- most previous laboratory studies investigated the activation rates of solids-associated viruses after the inactivation of free viruses inoculated into sludge first day of digestion may be very much slower (around immediately prior to digestion. However, to simulate 1 log unit every 2-7 days). In addition, most digesters more exactly real operating conditions it is necessary are operated by continuous, or regular, addition and to allow the viruses to become associated with solids removal of sludge. Therefore, some sludge has a prior to commencing digestion. Sanders therefore retention time of very much less than the design value investigated the inactivation by anaerobic digestion of and will contain significant concentrations of viruses solids-associated poliovirus and found that survival after digestion. It is probable that only batch digestion was enhanced by solids incorporation. The in- at 35°C, for 35 days, or digestion at temperatures of activation rates at 34 and 37°C were 84 to 99 percent around 50°C, will produce a virus-free sludge. More per day, respectively, for the first 24 hours. After that field data are required, on the actual virus removal time inactivation slowed considerably to between 30 performance of operating plants of these types, to and 60 percent per day. At 50°C the inactivation rate confirm this assumption. was high at more than 7 log units per day. Berg and Metcalf (1978) reported the destruction of between 76 and 96 percent of viruses by mesophilic By drying digestion (35°C for 20 days) and between 98.9 and > 99.9 percent by thermophilic digestion (50°C for 20 Both raw and digested sludges are normally days). Enterovirus concentrations in raw sludge were dewatered prior to disposal, and the most common 4 x 103 to > 1 x 105 per liter, 300 to 4,100 per liter in technique is spreading on outdoor sludge drying beds. mesophilically digested sludge, and 0 to 170 per liter in Very little information is available on virus removal by thermophilically digested sludge. In these experiments, sludge drying (see below and the appendixes of samples of digested sludge were taken shortly after the Feachem and others 1980), and no studies have been addition of fresh sludge to the digesters, and so reported from developing countries. However, the data theoretical retention times would not have applied to on enterovirus survival in sludge are also relevant (see all aliquots of digested sludge. the section above on the occurrence and survival of Wellings, Lewis and Mountain (1976) isolated enteroviruses in sludge and the appendixes of Feachem enteroviruses and reoviruses, at concentrations of up to and others 1980). 34 per liter, from sludge from an anaerobic digester in Ward and Ashley (1977b) investigated the in- Florida (retention time >60 days at 34°C) to which no activation of viruses in sewage sludge that occurs raw sludge had been added for the previous 7 days. during dewatering by evaporation. Sludge, with a Sattar and Westwood (1979) found excreted viruses in solids content of 5 percent and a pH of 6, was 53 percent of samples of digested sludge (20 days at inoculated with 2.7 x 107 viruses per milliliter and air 35°C) and in 39 percent of dried sludge samples (>6 dried at 21°C in 1 centimeter thick layers over 4 days. months' drying time) at a large sewage treatment plant As evaporation proceeded, poliovirus 1 was in- in Ottawa (Canada). Hurst and others (1978) isolated activated at a low but constant rate until, at a solids viruses, at concentrations of up to 231 per liter, from concentration of 65 percent, approximately 75 percent sludge that had been thickened, aerobically digested, inactivation had occurred. At this stage inactivation 162 ENVIRONMENTAL BIOLOGY & EPIDEMIOLOGY: VIRUSES increased rapidly so that, during concentration up to present at the high pH levels found in anaerobically 83 percent solids, a further 99.9 percent inactivation digested sludge. At 43°C after 200 minutes, poliovirus occurred. Further concentration up to 91 percent concentration was reduced by over 3 log units in solids produced little more inactivation. A similar digested sludge, but it was almost stable in raw sludge. result was obtained with coxsackievirus BH and At 51°C, the poliovirus concentration was reduced by reovirus 3. In a subsequent study (Ward and Ashley over 5 log units in under 5 minutes in digested sludge 1978b), it was found that sludge drying increased the and by over 4 log units after 50 minutes in raw sludge. heat required to inactivate enteroviruses and reovirus. In a second study (Ward and Ashley 1977c), the heat Sattar and Westwood (1979) isolated viruses from inactivation of reovirus 3 in sludge was investigated. anaerobically digested sludge that had been drying for Reovirus was found to be quite heat resistant 8 months in Canada. Wellings, Lewis and Mountain compared with poliovirus but was not protected (1976) isolated 10 enteroviruses per 100 grams of against heat inactivation by sludge. At 50°C for 20 sludge that had been on sludge drying beds for two minutes, reovirus concentrations were reduced by 4 log weeks during February in Florida (USA). units in digested sludge and by 2 log units in raw 'These studies, and the reports on virus survival in sludge. At 60°C after 20 minutes; the reductions were 5 sludge indicate that during cool, wet weather en- log units in digested sludge and 4 log units in raw teroviruses may survive in drying sludge for several sludge. A virucidal agent against reoviruses was months. Data on rapid virus inactivation at solids discovered in the sludge that had greatly increased concentrations between 65 and 83 percent may be activity at pH values above 8. Unlike the case of the irrelevant, since under temperate conditions sludges enteroviruses (Ward and Ashley 1977a), this agent was may achieve a solids content of only about 25 percent not ammonia. A follow-up study (Ward and Ashley after about 2 months on a drying bed. Even in Texas 1978a) determined that ionic detergents found in (USA) in the summer, a sludge that had been applied to sewage sludges reduce the heat required to inactivate land for 3 months had dried to only 59 percent solids reoviruses (cationic detergents being more active than (Hurst and others 1978). However, a comparison anionic detergents, and nonionic detergents having no between virus inactivation rates in sludge during activity). In contrast, some detergents were found to Danish winters (1 log unit per month), and during protect poliovirus against heat inactivation. (More Texan summers (2 log units per week), clearly indicates information on the virucidal activity of detergents, and that enterovirus inactivation is far more rapid in hot the effects of differing pH values, is given in Ward and climates under bright sunshine. A good virus removal Ashley 1979). In a subsequent study (Ward and Ashley performance may therefore be obtained by sludge 1978b), a reduction in moisture content was found to drying beds in many developing countries, and field reduce significantly the rates of heat inactivation of studies are required to confirm this possibility. both enteroviruses and reovirus. Poliovirus in raw sludge at 51°C was reduced by over 5 log units in 5 minutes when the sludge had 5 percent solids but by By heating less than 2 log units after 100 minutes when the sludge had an 80 percent solids content. Reovirus in raw Under certain circumstances enteroviruses can be sludge at 51 °C was reduced by 4 log units in 50 minutes remarkably resistant to heating. For instance, Larkin when the sludge had 5 percent solids and by less than 2 and Fassolitis (1979) reported that infectious ribonuc- log units after 50 minutes when the sludge had a solids leic acid (RNA) liberated from poliovirus 1 and content of 80 percent. coxsackievirus B2 could withstand 65 minutes at 70°C. When compared with the reality of sludge treatment In general, however, heat is a potent virucide, and the processes, however, these are trivial differences and heating of sludges, or their digestion at elevated distinctions. Figure 9-2 presents data on the survival of temperatures, is an effective method of virus in- different types of enteroviruses under different activation. conditions for various time-temperature combi- Ward, Ashley and Moseley (1976) studied the effect nations. A conservative upper bound is drawn, above of raw and anaerobically digested sludge on the heat which the combinations of time and temperature inactivation of poliovirus. Raw sludge was found to be should guarantee enterovirus elimination. From this very protective of poliovirus inactivation whereas figure it is postulated that holding sludge at 30°C for 3 digested sludge was not, and subsequent studies (Ward months, at 40°C for 2 weeks, at 50°C for 1 day, or at and Ashley 1977a) determined that this difference was 60'C for 2 hours, will inactivate all enteroviruses, due to the virucidal activity of uncharged ammonia reoviruses, and adenoviruses. ENTEROVIRUSES, POLIOMYELITIS, AND SIMILAR INFECTIONS 163 OD - so8 75 -75 70 - ZONE -70 65 - Z65 60 - OF -60 55 -SAFETY -5s .~45- 4 -40 35 -3 '30 - IL IL 25 - 25 20 - s IL s O- 20 15 * 100% inactivation of nterovirus 15 10 | 1e ta n I00% inactivation of entorovirusm | 10 5 - it * X* 5 0.0) o'. 1 b I I lio io oo Insin Ihow 1d, Iw& Imonth lyom TIME (HOURS) Figure 9-2. The influence of time and temperature on enteroviruses. The data probably also apply to adenoviruses and reoviruses. The points plotted are the results of experiments done under widely differing conditions. The line drawn represents a conservative upper boundary for death By composting seeded bacteriophage (originally present at a con- centration of 106 per gram) took about 50 days in Aerobic thermophilic composting is an effective composting raw sludge and up to 70 days in method of inactivating viruses in sludge if all parts of composting digested sludge. Naturally occurring the pile or mass are heated to 50°C or above for enteric viruses were isolated throughout the windrow sufficient time (see figure 9-2 and the appendixes of phase of the composting but were never isolated from Feachem and others 1980). the curing piles. All these experiments were conducted Krige (1964) reported that seeded poliovirus 1 was during the cold and wet months of October-March. eliminated from a sludge, grass, and refuse mixture Experiments were later conducted into the inactivation composted at 38-58°C for 7 days. Wiley and of seeded coliphage f2 by a forced air composting Westerberg (1969) determined that the thermal death system (21 days of aerated composting followed by 30 points for poliovirus 1 were 60°C for 5 minutes or 55°C days of curing) at the same site (Burge, Cramer and for 30 minutes. When poliovirus 1 was added to a Epstein 1978). Temperatures rose to 50°C and above forced-air sludge-composting unit operating at within the first five days, and coliphage destruction 60-76°C, it could not be detected after 1 hour. deep in the pile was complete within 13 days. However, Kawata, Cramer and Burge (1977) reported the at the edge of the pile, very small proportions (around inactivation of seeded bacteriophage f2 in a sludge and 0.001 percent) of virus survived after 21 days. The wood chips mixture composted at a plant in Maryland inactivation rate in the pile was approximately 1 log (USA). The mixture was formed into windrows, which unit per 2 days. Pile temperatures in the forced air were turned regularly (up to once per day depending system were unaffected by ambient temperature or upon the temperature within the mass) for 2 weeks and rainfall. were then made into large piles for 4 weeks of curing. Much more research is required on virus removal When raw sludge was composted, the temperatures from various types of composting system using night rose to 50-70°C within 3 days and remained there soil, sludge, refuse, woodchips, and other materials. except for short periods following rainstorms. When Pending this work, virus inactivation may be digested sludge was composted, the temperature rose tentatively predicted from figure 9-2. Even where the gradually to 40-60°C after 10-14 days, and during time-temperature characteristics in the pile are well cold wet winter weather the temperatures rose only to within the safety zone in figure 9-2, virus survival may the 20-30°C range. Complete inactivation of the still be occurring at the edges of the pile, which are 164 ENVIRONMENTAL BIOLOGY & EPIDEMIOLOGY: VIRUSES usually much cooler, especially during rain. Complete Anon. (1976). Shellfish and public health. British Medical elimination of enteroviruses is therefore dependent Journal, 2, 1-2. upon pile management techniques such as turning, Anon. (1978). Viruses and reclaimed water. British Medical lagging, or forced aeration. Journal, 2, 1662. Balluz, S. A., Bulter, M. and Jones, H. H. (1978). The behaviour of f2 coliphage in activated sludge treatment. By other sludge treatment processes Journal oJ Hygiene, 80, 237-243. Balluz, S. A., Jones. H. H. and Butler, M. (1977). The persistence of poliovirus in activated sludge treatment. tures of 50'C or above should yield a virus-free product Journal of Hygiene, 78, 165- 173. if the process is well controlled and carried out for Bausum, H. T., Schaub, S. A. and Kenyon, K. F. (1978). Viral sufficiently long to ensure that all parts of the mass are and Bacterial Aerosols at a Wastewater Spray Irrigation heated. This latter point is particularly important when Site. Technical Report 7804. Washington, D.C.: US Army continuous, rather than batch, processes are being Medical Research and Development Command. used. Examples include pasteurization (70-80°C), Baylor, E. R., Baylor, M. B., Blanchard, D. C., Syzdek, L. D. anaerobic or aerobic thermophilic digestion and Appel, C. (1977). Virus transfer from surf to wind. (46-55°C), wet oxidation (180-220°C), incineration Scienzce, 198, 575-580. (over 650C), and pyrolysis, as well as heating and Baylor, E. R., Peters, V. and Baylor, M. B. (1977). Water-to- composting (discussed above), air transfer of virus. Science, 197, 763-764. Berg,G.ed.(1967).Trani,sminssion of, l , l. Wiatei Route. Sludge disinfection by irradiation with high-energy New York: Wiley Interscience. electrons is attracting increasing interest. (Osborn and . 1973) Removal ofviruses from sewage, effluents. and Hattingh 1978). The few data available on virus waters: a review. Bulletin of the World Heulth Organization. inactivation in sludge by irradiation indicate a rather 49, 451-460. poor removal of 75-90 percent after the application of , (1978a). Detection, occurrence and removal of 3-5 kilograys.7 (Lessel and Suess 1978; Sullivan and viruses. Journal ot the Water Polltutionz Conztrol Federatioz., others 1971; Ward 1977). Sludge protects poliovirus 50. 1395-1402. from irradiation, but little or no extra protection is , ed. (1978b). Indicators ojf Viruses in Water anid Food. afforded by increasing solids content above about 1 Ann Arbor, Mich.: Ann Arbor Science Publishers. percent (Ward 1977). Superchlorination or chlorine Berg, G., Dean. R. B. and Dahling, R. D. (1968). Removal of percent (Ward 197.uecpoliovirus 1 from secondary effluents by lime flocculation oxtdation (the application of 700-4,000 milligrams per and rapid sand filtration. Journal of the American Water liter of chlorine under pressure) may inactivate most Works Association, 60, 193-198. viruses in sludge but has been objected to because it Berg, G. and Metcalf, T. G. (1978). Indicators of viruses in proliferates chlorinated organic compounds in the waters. In Indicators ofjViruses in Water and Food, ed. Berg, environment (Kamlet 1979). G.. pp. 267-296. Ann Arbor. Mich.: Ann Arbor Science Most of these technologies for sludge disinfection Publishers. are still in the research and development stage, and Berry. S. A. and Noton, B. G. (1976). Survival of many of them will prove to be too costly and too bacteriophages in seawater. Water Research, 10, 323-327. technically complex to be appropriate in most Bertucci, J. J., Lue-Hing, C., Zenz, D. and Sedita, S. J. (1977). situations in developing countries. Inactivation of viruses during anaerobic sludge digestion. Jour nal of the Water Pollutioni Control Feder ationl, 49, 1642- 1651. 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In Proceedings of the Third Applied and Environmental Microbiology, 35, 290-296. International Conference on Water Pollution Research. pp. Thraenhart, O., Omar, A., Habib, A. and Miakhail, M. R. 37-44. Washington, D.C.: Water Pollution Control (1970). Poliomyelitis surveillance in Kabul City. Federation. Zentralblatt fur Bakteriologie, Parasitenkunde, Infek- Slade, J. S. and Edworthy, K. J. (1981). Virology of tionskrankheiten und Hygiene, 1, 213, 319-324. wastewater recharge of the chalk aquifer. II. Microbiology Tierney, J. T., Sullivan, R. and Larkin, E. P. (1977). and water quality. In Viruses and Wastewater Treatment, Persistence of poliovirus 1 in soil and on vegetables grown eds. Goddard, M. and Butler, M. Oxford: Pergamon. in soil previously flooded with inoculated sewage sludge or Slanetz, L. W., Bartley, C. H., Metcalf, T. G. and Nesman, R. effluent. Applied and Environmental Microbiology, 33, (1970). Survival of enteric bacteria and viruses in 109-113. municipal sewage lagoons. In Proceedings of the Second Vaughn, J. M., Landry, E. F., Baranosky, L. J., Beckwith, C. International Symposium Jor Water Treatment Lagoons, A., Dahl, M. C. and Delihas, N. C. (1978). Survey of human ed. McKinney, R. E., pp. 132-141. Kansas City: Missouri virus occurrence in wastewater-recharged groundwater on Basin Engineering Health Council. Long Island. Applied and Environmental Microbiology, 36, Small-Scale Waste Management Project (1978). 47-51. Management of Small Waste Flows. Report EPA-600/2-78- Vaughn, J. M., Landry, E. F., Thomas, M. Z., Vicale, T. J. and 173. Cincinnati, Ohio: US Environmental Protection Penello, W. F. (1979a). Survey of human enterovirus Agency. occurrence in fresh and marine surface waters on Long Smith, E. M., Gerba, C. P. and Melnick, J. L. (1978). Role of Island. 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In Virus Survival transfer model for virus transport in soils. Water Research, in Water and Wastewater Systems, eds. Malina, J. F. and 14, 783-790. Sagik, B. P., pp. 241-252. Austin Texas: Center for Wallis, C. and Melnick, J. L. (1967). Concentration of viruses Research on Water Resources, University of Texas at on aluminum and calcium salts. American Journal of Austin. Epidemiology, 85, 459-468. Sproul, 0. J. (1976). Removal of viruses by treatment Ward, R. L. (1977). Inactivation of poliovirus in wastewater processes. In Viruses in Water, eds. Berg, G., Bodily, H. L., sludge with radiation and thermoradiation. Applied and Lennette, E. H., Melnick, J. L. and Metcalf, T. G., pp. Environmental Microbiology, 33, 1218-1219. 167-179. Washington, D.C.: American Public Health Ward, R. L. and Ashley, C. S. (1976). Inactivation of Association. poliovirus in digested sludge. Applied and Environmental (1980). Critical Review of Virus Removal by Microbiology, 31, 921-930. Coagulation Processes and pH Modifications. Report EPA- (1977a). Indentification of the virucidal agent in 600/2-80-004. Cincinnati, Ohio: US Environmental wastewater sludge. Applied and Environmental Protection Agency. Microbiology, 33, 860-864. Stagg, C. H., Wallis, C., Ward, C. H. and Gerba, C. P. (1978). (1977b). Inactivation of enteric viruses in wastewater Chlorination of solids-associated coliphages. Progress in sludge through dewatering by evaporation. Applied and Water Technology, 10, 381-387. Environmental Microbiology, 34, 564-570. Stander, G. J. and Clayton, A. J. (1977). Planning and (1977c). Discovery of an agent in wastewater sludge 172 ENVIRONMENTAL BIOLOGY & EPIDEMIOLOGY: VIRUSES that reduces the heat required to inactivate reovirus. Wiley, B. B. and Westerberg, S. C. (1969). Survival of human Applied and Environmernal Microbiology, 34, 681-688. pathogens in composted sewage Applied Microbiology, 18, (1978a). Identification of detergents as components 994-1001. of wastewater sludge that modify the thermal stability of Wolf, H. W., Safferman, R. S., Mixson, A. R. and Stringer, C. reovirus and enteroviruses. Applied and Environmental E. (1974). Virus inactivation during tertiary treatment. In Microbiology, 36, 889-897. Virus Survival in Water and Wastewater Systems, eds. (1978b). Heat inactivation of enteric viruses in Malina, J. F. and Sagik, B. P., pp. 145-157. Austin, Texas: dewatered wastewater sludge. Applied and Environmental Center for Research in Water Resources, University of Microbiology, 36, 898-905. Texas at Austin. - (1979). pH modification of the effects ofdetergentson Won, W. D. and Ross, H. (1973). Persistence of virus and the stability of enteric viruses. Applied and Environmental bacteria in seawater. Journal of the Envlironmental Microbiology, 38, 314-322. Engineering Division, American Society oJ Civil Engineers, Ward, R. L., Ashley, C. S. and Moseley, R. H. (1976). Heat 99, 205-211. inactivation of poliovirus in wastewater sludge. Applied Wood, P. C. (1979). Public health aspects of shellfish from and Environmental Microbiology, 32, 339-346. polluted water. In Biological Indicators of Water Quality, Watson, P. G. (1977). A virological survey of polluted eds. James, A. and Evison, L., pp. 13/1-13/18. Chichester: seawater. Journal of Applied Bacteriology, 43, 11-12. John Wiley. Wetlings, F. M., Lewis, A. L. and Mountain, C. W. (1974). Yeager, J. G. and O'Brien, R. T. (1977). Enterovirus and Virus survival following wastewater spray irrigation of bacteriophage inactivation in groundwater and translo- sandy soils. In Virus Survival in Water and Wastewater cation in soil. Abstract N57. Abstracts of the Annual Systems, eds. Malina, J. F. and Sagik, B. P., pp. 253-260. Meetinig of the American Society jbr Microbiology. Austin, Texas: Center for Research in Water Resources, Washington, D.C. University of Texas at Austin. (1979a). Enterovirus inactivation in soil. Applied and (1976). Demonstration of solids-associated virus in Environmental Microbiology, 38, 694-701. wastewater and sludge. Applied and Entvironmental (1979b). Structural changes associated with po- Microbiology, 31, 354-358. liovirus inactivation in soil. Applied and Environmental Wellings, F. M., Lewis, A. L., Mountain, C. W. and Pierce, L. Microbiology, 38, 702-709. V. (1975). Demonstration of virus in groundwater after Young, D. C. and Sharp, D. G. (1977). Poliovirus aggregates effluent discharge onto soil. Applied Microbiology. 29, and their survival in water. Applied and Environmental 751-757. Microbiology, 33, 168-177. Wellings, F. M., Mountain, C. W. and Lewis, A. L. (1976). Zdrazilek, J., Sramova, H. and Hoffmanova, V. (1977). Virus in groundwater. In Second National Conference on Comparison of poliovirus detection in sewage and stool Individual On-site Wastewater Systems, pp. 61-65. Ann samples: a study in a creche in the third week after Arbor, Mich.: National Sanitation Foundation. vaccination. International Journal of Epidemiology, 6, WHO (1979). Human Viruses in Water, Wastewater and Soil. 169-172. Technical Report Series no. 639. Geneva: World Health Organization. 10 Hepatitis A Virus and Infectious Hepatitis MUCH OF THE WORK on poliovirus and other Recently a third form of viral hepatitis has been enteroviruses in the environment described in chapter described: non-A:non-B hepatitis. This new form of 9 was inspired by an interest in other excreted viruses hepatitis is now known to be the most common type of that cause major public health problems but cannot be post-transfusion hepatitis in some areas. Non-A: non-B routinely isolated at the present time. Foremost among hepatitis may prove to be divisible into more than one these other excreted viruses is hepatitis A virus, which form. As far as is known, only hepatitis A is primarily is a common and important cause of disease an excreted infection, and therefore it alone will be throughout the world. discussed in this chapter. The study of the hepatitis viruses is a rapidly moving field of research hepatitis A virus was not identified in fecal extracts until 1973, although the Identfication disease it causes has been recorded by civil and military The clinical picture of viral hepatitis varies in its historians since the fifth century BC. This chapter is presentation from inapparent or subclinical infection, brief, because little is known at the time of writing about to slight malaise, mild gastrointestinal symptoms hepatitis A virus in the environment, and tentative, and the anicteric (without jaundice) form of the because the rate of scientific progress is rapid, and much disease, to acute icteric iliness, severe prolonged new information will come to light in the next few years. jaundice, and chronic liver disease. The anicteric form A recent and comprehensive account of the hepatitis is characterized by malaise, anorexia, various gastro- viruses is given by Zuckerman and Howard (1979). intestinal disturbances, an enlarged and tender liver, and perhaps a fever. In acute icteric infections these symptoms may be more pronounced and may be Description of Pathogen and Disease followed after 5-10 days by dark urine, clay-colored stools, and jaundice, which persists commonly for 1-2 Two distinct forms of viral hepatitis have been weeks. Typically, the disease is especially mild in recognized: hepatitis A (also known as infectious children, for whom the ratio of anicteric to icteric hepatitis, epidemic hepatitis, or epidemic jaundice) illness may be 10 or more to 1. Convalescence usually is and hepatitis B (also known as serum hepatitis). prolonged. In general, severity increases with age, but They differ in etiology and in some epidemio- complete recovery without sequelac or recurrences is logical, immunological, clinical, and pathological the rule. Many mild cases without jaundice, especially characteristics. From the environmental viewpoint, in children, are recognizable only by liver-function or the primary distinction between them is that serum-enzyme tests. hepatitis A is transmitted by the fecal-oral route, whereas hepatitis B is normally transmitted by infected blood or tissue fluid (for instance, during blood Occurrence transfusion, injection, immunization, tattooing, and Viral hepatitis type A occurs endemically in all parts acupuncture) but may also rarely be transmitted by of the world, with frequent reports of minor and major saliva, semen, breastmilk, other body fluids, and feces if outbreaks. The exact incidence is difficult to estimate contaminated with blood. Because of these differences because of the high proportion of subclinical infections in mode of transmission, the approaches to prevention and infections without jaundice, differences in sur- and control of hepatitis A and B are very different. veillance, and differing patterns of disease. The degree 173 174 ENVIRONMENTAL BIOLOGY & EPIDEMIOLOGY: VIRUSES of underreporting is very high; even in developed Reservoirs countries with compulsory notification, it is doubtful Man is almost certainly the important reservoir for whether more than 50 percent of cases of jaundice are human hepatitis A infection. However, cases have been actually reported. Bctuause seprogia reported that suggest transmission to man from Because serological tests for hepatitis A antibody are chmaze,grls,Cebsps,ibo,an now available, it has become possible to study the chimpanzees, gorillas, Celebes apes, gibbons, and incidence and it he paisAinfections in woolly monkeys. Antibodies to hepatitis A virus are andidenceau ion vparios gfeog hicl found in nonhuman primates, and susceptible chimpan- different populations zees and marmosets are readily infected in the areas. A recent survey of sera for hepatitis A antibody laboratory. by immune adherence hemagglutination from samples of healthy adults, mostly volunteer blood donors, from seven geographical populations has shown that the age-standardized prevalence of hepatitis A antibody Transmission was 29 percent in Switzerland, 45 percent in the USA, Hepatitis A virus is spread by the fecal-oral route, 76 percent in Senegal, 81 percent in Belgium, 89 percent most commonly by person-to-person contact, and in Taiwan, 95 percent in Israel, and 97 percent in infection occurs readily in conditions of poor Yugoslavia (Szmuness and others 1977). This survey sanitation and overcrowding. Common-source out- confirmed that infections with hepatitis A virus are breaks are most frequently initiated by fecal con- widespread throughout the world. tamination of water and food, but waterborne transmission is not a major factor in the maintenance of this infection. Ingestion of shellfish cultivated in Infectious agent polluted water is associated with a high risk of Small cubic particles measuring 27 nanometers have acquiring hepatitis A. been seen by electron microscopy in infective feces of human subjects (see figure 10-1). The virus contains single-stranded RNA and has the biochemical and Incubation period biophysical properties of a picornavirus. The incubation period of hepatitis A is between 3 rx 4ib,, and 5 weeks, with a mean of 28 days. Period of communicability * t ^ , Hepatitis A virus is shed in the stools primarily - i iduring the period from 2 weeks before, to 2 weeks after, the onset of symptoms; in other words, for up to 4 weeks commencing 1-3 weeks after infection. * Persistent carriage or excretion of hepatitis A virus in humans does not occur. Resistance Susceptibility is general. Low clinical incidence in infants and preschool children suggests that mild and anicteric infections are common. The degree and duration of homologous immunity after attack are unknown but presumed to be long lasting. Figure 10-1. Hepatitis A viruses under transmission Epidemiology electronmicroscopy. Scale bar = 0.1 micrometers. (Photo: A. J. Zuckerman and A. Thornton, London All age groups are susceptible to hepatitis. Until School of Hygiene and Tropical Medicine, London, recent years the highest incidence in the civilian UK) population was observed in children of school age, but HEPATITIS A VIRUS AND INFECTIOUS HEPATITIS 175 in a number of countries, including Sweden and the USA). Antibody was not detected in any individual USA, as many as 60-70 percent of notified cases now under 20 years old, and the highest age-specific occur in adults. This shift in age incidence in the prevalence for hepatitis A antibody was 59 percent in developed countries is reminiscent of the changing the 40-49 age group. Antibody prevalences were pattern of poliomyelitis (see chapter 9) and may reflect higher among institutionalized individuals in reduced transmission, caused by improved socioecon- Philadelphia. Szmuness and others (1976) studied 947 omic conditions, which defers infection to an older age randomly selected individuals in New York City group when the clinical consequences are usually more (USA) and found an overall prevalence of hepatitis A severe. antibody of 45 percent. Lower social classes had In conditions of poor hygiene, it is probable that significantly higher prevalences (72-80 percent) than transmission of hepatitis A virus occurs among higher social classes (18-30 percent). Jews had a children by direct fecal-oral routes. This leads to a significantly lower prevalence (7 percent) than other high incidence of subclinical or very mild infections whites (39 percent), but sex and homosexuality did not that confer substantial immunity. Moritsugu and affect prevalence. Antibody prevalence was closely others (1979) found that 92 percent ofchildren under 9 related to age in all groups; for instance, among years old in Colombo (Sri Lanka) had evidence of Chinese the prevalence rose to over 90 percent by the antibodies to hepatitis A virus. In Costa Rica age of 40 years. For both blacks and whites, antibody (Villarejos and others 1976), age-specific antibody prevalence was 2.5 to 4 times lower among individuals prevalences reached 80 percent by the age of 9 years. In with postgraduate education than among those Liberia, 90 percent of children over 5 years old in both without. urban and rural areas had hepatitis A antibodies These various studies show clearly that transmission (Willcox and others 1980). Similar results have been of hepatitis A virus is more common, and thus the obtained from Kenya (Wankya and others 1979) and prevalence of antibodies among children is higher, from Fiji, Tuvalu (formerly Ellice Islands), Niue, Cook among people of lower socioeconomic and educational Islands, and Western Samoa (Gust, Lehmann and status. This relationship can be detected both between Dimitrakakis 1979). and within countries. These and other aspects of In developed countries, improved hygiene reduces hepatitis A epidemiology, as revealed by serological the incidence of hepatitis A infection in the young, but surveys, have been reviewed by Dienstag and others many people become infected at some time in life. Gust, (1978). Recent investigations of hepatitis A outbreaks Lewis and Lehmann (1978) examined the sera in day care centers in the USA have highlighted the (collected in 1954-55) of 959 people (mainly of low major role of children who are not toilet trained (those socioeconomic status) in Melbourne (Australia) and under 2 years old) in spreading the infection (Hadler found that the prevalence of those having hepatitis A 1980; Vernon 1980). antibodies as 38 percent in the 6 to 10 year olds, 56 In temperate zones the characteristic seasonal trend percent in the 20 year olds, and over 97 percent in those has been for a marked rise in incidence in the autumn over 40 years old. The sera were collected prior to mass and early winter months, with a progressive fall to a poliomyelitis vaccination campaigns, and it was found minimum in midsummer. that the age-related acquisition of poliovirus anti- bodies was extremely similar to hepatitis A antibodies. Control Measures This strengthens the possibility that the epidemiology and transmission of polio and hepatitis A infections The spread of infection is reduced by simple hygienic may be similar and that they share a common response measures and the sanitary disposal of excreta. Normal to improved hygiene. A repeat survey in Melbourne in human immunoglobulin may prevent or attenuate a 1975 found antibody prevalences of 23 percent in 6 to clinical illness but may not always prevent the 10 year olds, 45 percent in 20 year olds, and 66 to 97 infection. The use of normal immunoglobulin is of percent in those over 40 years old (Gust and others value in the control of outbreaks of infection in specific 1978). The decrease in antibody prevalence pre- circumstances, such as in institutions and nursery sumably reflects an improvement in economic and schools. Following the recent development of a tissue environmental conditions between the mid- 1950s and culture technique for hepatitis A virus, hopes of the mid-1970s. developing a specific vaccine are high. The epide- Villarejos and others (1976) found low prevalence of miology of hepatitis A infection, and approaches to its hepatitis A antibody among people of high socioecon- control, would be altered considerably by the omic status in the Philadelphia area (Pennsylvania, widespread use of such a vaccine. 176 ENVIRONMENTAL BIOLOGY & EPIDEMIOLOGY: VIRUSES Occurrence and Survival in the seepage from cesspools traveling a horizontal distance Environment of 23-55 meters through fissured red shale and limestone to pollute a well 67 meters deep. Similarly, 24 There is no direct evidence of the behavior or cases of hepatitis A occurred among 180 residents of occurrence of hepatitis A virus in the environment holiday cottages near Pilsen (Czechoslovakia) when because the virus has never been isolated from an their well was contaminated by seeping sewage (Vilim environmental sample. Such isolations must await and others 1977). However, there is no evidence that the development of sensitive and specific serological water conforming to conventional bacteriological techniques for detecting small amounts of hepatitis A criteria has ever caused hepatitis A, and the disease antigen or routine tissue culture techniques. The recent occurs under conditions similar to those which lead to successful propagation of hepatitis A virus in other waterborne, fecal-oral outbreaks of disease marmoset liver, fetal rhesus monkey kidney, and other (Grabow 1976). cells gives hope that tissue culture techniques will Known waterborne cases of hepatitis A in the USA become available soon. range between 35 and 120 year, which is only about 0.4 The available evidence on hepatitis A virus in the percent of total reported cases. Recent studies have environment is indirect. The knowledge that hepatitis sought to associate hepatitis incidence in the USA A incidence is high in some communities leads to the with raw water quality, water treatment practices, or assumption that hepatitis A virus may be present old distribution systems. However, many of these where fecal pollution is present, and especially where physical parameters are associated with socioecon- high concentrations of enteroviruses are present (see omic status in the area, and it is well established that chapter 9). However, far too little is known about the hepatitis A incidence is higher in poor and deprived prevalence of hepatitis A virus excretion, or the communities. To clarify the situation, Batik and others iiumbers of virus particles excreted, to predict at what (1980) compared hepatitis incidence with water supply concentration hepatitis A virus might be found in, for factors among a sample of nearly 3 million people who instance, sewage. Some evidence is provided by experienced 11,633 reported cases of hepatitis A during outbreaks of hepatitis A infection that can be traced by 1965-77. The comparisons were controlled for age epidemiological analysis to a particular source, such as distribution, educational levels, population density, contaminated water or food or shellfish. and poverty. None of the water supply source or Many outbreaks of hepatitis have been linked to treatment variables were significantly correlated with polluted drinking water. An explosive outbreak hepatitis A incidence. occurred in New Delhi in December-January 1955-56 Another source of circumstantial evidence of (Viswanathan 1957). About 30,000 cases were reported hepatitis A virus behavior in the environment are the (presumably many cases were subclinical or went many documented accounts of hepatitis outbreaks unreported) when sewage contaminated the city water associated with contaminated shellfish (Gerba and supply after heavy rain. This outbreak produced Goyal 1978; Hughes, Merson and Gangarosa 1977; evidence that this presumed hepatitis A virus-like strain Levin 1978). As many as 8.6 percent of reported is more resistant to chlorination than some enteric hepatitis A cases in the USA are associated with bacteria, and this is predictable from the data on the shellfish consumption (Levin 1978), usually with effect of chlorination on enteroviruses (see chapter 9). A consumption of raw oysters and raw or steamed clams. more recent report from India (Newaskar, Vidwans and Koff and others (1967) interviewed 270 adult hepatitis Vachha 1978) also suggests a link between sewage patients in Boston (Massachusetts, USA) hospitals and contamination of water supplies and an outbreak of concluded that ingestion of raw or steamed shellfish hepatitis in Maharashtra. was as common a source of infection as contact with Numerous small outbreaks attributed to water jaundiced persons, even during a nonepidemic period. pollution are reported from North America and An outbreak of hepatitis A (278 cases) that occurred Europe (see Craun 1978). These outbreaks typically in Louisiana during October and November 1973 was are associated with contamination of the water investigated and shown to be related to simultaneous distribution system by cross-connection or back- outbreaks in Texas and Georgia (USA). The outbreak siphonage or with the use of small untreated rural was attributed to the consumption of contaminated water supplies that are contaminated by sewage oysters harvested from approved growing areas on the discharges or leaks. Neefe and Stokes (1945) reported east Louisiana coast. The oysters were probably an outbreak of 350 cases over 13 weeks at a summer polluted when contaminated river water was dischar- camp in the USA. The outbreak was attributed to ged into the area during floods earlier in the year. HEPATITIS A VIRUS AND INFECTIOUS HEPATITIS 177 Oyster fishing was prohibited while the counts of It is to be expected that isolation and enumeration coliform bacteria were in excess of 70 per 100 milliliters. techniques for hepatitis A virus will become available Oysters harvested some 4 weeks after the coliform over the next few years and will be followed by a surge counts fell below this limit led to the disease outbreak. of investigations into the inactivation of the virus by The evidence suggests that the oysters concentrated the sewage treatment processes. In the meantime, it is hepatitis virus and retained it for a period of 1.5-2 reasonable to assume that hepatitis A virus behaves in months. A more severe outbreak was probably avoided a way similar to the enteroviruses (chapter 9). This because oysters in heavily contaminated areas were assumption will become more plausible if it is killed by changes in salinity (Mackowiak, Caraway confirmed that hepatitis A virus is an enterovirus. and Portnoy 1976; Portnoy and others 1975). On the basis of the epidemiological evidence, there is good reason to believe that shellfish accumulate and Inactivation b Night Soil and Sludge retain hepatitis A virus from polluted waters in the Tratment Proegs sg same way that they accumulate and retain poliovirus Treatment Processes (chapter 9). There is also good epidemiological evidence that cooking of shellfish does not necessarily As with sewage treatment processes, no direct inactivate all hepatitis A virus, just as it does not evidence is available on the inactivation of hepatitis A necessarily inactivate all poliovirus. Recent virus by night soil or sludge treatment processes. A confirmation of this was provided by Peterson and study by Ragka and others (1966) provided indirect others (1978), who reported that hepatitis A virus evidence of hepatitis A virus survival in cesspool sludge injected into oysters and treated at 60'C for 19 minutes applied to farm land. During the winter months of could still induce acute disease and seroconversion December and January (1962-63), cesspool sewage when fed to fasted marmosets. was spread on farmland near a small stream used as the source of water for a dairy near Jablonec (Czechoslovakia). On March 11-13 a thaw combined Inactivation by Sewage Treatment with rain led to the contamination of the stream. The Processes organic content of the water was sufficient to overwhelm the chlorination of the supply, and The lack of isolation techniques for hepatitis A virus contaminated water was used by the dairy. The water has prevented any direct studies on the inactivation of treatment process included chlorination followed by the virus by sewage treatment. Indirect evidence on the sand filtration. An epidemic of hepatitis A spread by reaction of hepatitis A virus to chlorination is provided dairy products occurred during April-June. There by the work of Neefe and others (1947), who were 424 cases, with the highest incidence in the 15-20 contaminated water with feces known to contain age group. Relatively few contact cases occurred hepatitis A virus, subjected the water to various possibly due to the mass administration of gamma treatment regimes, and then asked volunteers to drink globulin, particularly to children. The average it. The results indicated that coagulation and filtration incubation period was 45 days. There was no increase reduced but did not eliminate hepatitis A virus but that in other enteric infections, and the authors attribute coagulation, filtration, and chlorination (to provide 0.4 this either to a lack of the disease organisms in the milligrams per liter of free residual chlorine after 30 sewage or to the marginal chlorination having been minutes) eliminated the virus. However, direct sufficient to inactivate bacterial pathogens. It is evident chlorination of the contaminated water (to provide a from the information supplied that under cold weather total chlorine residual after 30 minutes of 1 milligram conditions hepatitis A virus survived at least 5 to 6 per liter) did not prevent infection in the volunteers, weeks in sewage spread on farmland. whereas heavier chlorine doses applied to the There is some evidence that hepatitis A virus may be contaminated water (15 milligrams per liter of total more resistant to heat than the enteroviruses discussed chlorine after 30 minutes) rendered the water in chapter 9. Krugman, Giles and Hammond (1970) noninfective to all volunteers. These results suggest found that hepatitis A virus was rendered nonin- that hepatitis A virus, like the enteroviruses (see fectious and nonimmunogenic by treatment at 98°C for chapter 9), is insensitive to combined chlorine and may 1 minute. Deinhardt (1976) reported that some only be inactivated in sewage disinfection by the hepatitis A virus survived treatment at 60°C for 1 hour. application of heavy chlorine doses to highly purified However, ability to withstand fairly high temperatures effluents. (>.60°C) for short times (< 1 hour) may not be 178 ENVIRONMENTAL BIOLOGY & EPIDEMIOLOGY: VIRUSES indicative of the ability of the virus to withstand cooler outbreaks. Journal of the Water Pollution Control temperatures for longer periods (see figure 9-2). Federation, 50, 1377-1381. Mackowiak, P. A., Caraway, C. T. and Portnoy, B. L. (1976). Oyster associated hepatitis: lessons from the Louisiana experience. American Journal of Epidemiology, 103, Literature Cited 181-191. Moritsugu, Y., Miyamura, K., Utagawa, E., Kono, R., de la Batik, O., Craun, G. F., Tuthill, R. W. and Kraemer, D. F. Motte, P. U. and Forbes, C. A. L. (1979). Prevalence of (1980). An epidemiologic study ofthe relatioriship between antibody to hepatitis A virus in Sri Lanka. Asian Journal of hepatitis A and water supply characteristics and treatment. Inzfectious Diseases, 3, 33-36. American Journal oJ Public Health, 70, 167-168. Neefe, J. R., Baty, J. B.. Reinhold, J. G. and Stokes, J. (1947). Craun, G. F. (1978). Disease outbreaks caused by drinking Inactivation of the virus of infectious hepatitis in drinking water. Journal of the Water Pollution Control Federation, water. American Journal of Public Health, 37, 365-372. 50, 1362-1374. Neefe, J. R. and Stokes, J. (1945). An epidemic of infectious Deinhardt, F. (1976). Hepatitis in primates. Advances in Virus hepatitis apparently due to a water-borne agent. Jmaurnal oq Research, 20, 113-157. the American Medical Association. 128, 1063 1075. Dienstag, J. L., Szmuness, W., Stevens, C. E. and Purcell, R. Newaskar, L. D., Vidwans, A. H. and Vachha, S. M. (1978). H. (1978). Hepatitis A virus infection: new insights from Outbreak of viral hepatitis due to water pollution in seroepidemiologic studies. Journal of Infectious Diseases, Pimpri-Chinchwad township. Indian Journal of 137, 328-340. Environmental Health, 20, 79-83. Gerba, C. P. and Goyal, S. M. (1978). Detection and Peterson, D. A., Wolfe, L. G., Larkin, E. P. and Deinhardt, F. occurrence of enteric viruses in shellfish: a review. Journal W. (1978). Thermal treatment and infectivity ofhepatitisA of Food Protection, 41, 743-754. virus in human feces. Journal of Medical 1 , !. . 2, Grabow, W. 0. K. (1976). Progress in studies on the type A 201-206. (infectious) hepatitis virus in water. Water South Africa, 2, Portnoy, B. L., Mackowiak, P. A., Caraway, C. T., Walker, J. 20-24. A.. McKinley, T. W. and Klein, C. A. (1975). Oyster- Gust, I. D., Lehmann, N. I. and Dimitrakakis, M. (1979). A associated hepatitis: failure of shellfish certification seroepidemiologic study of infection with HAV and HBV programs to prevent outbreaks. Journal of the American in five Pacific islands. American Journal of Epidemiology, Medical Association, 233, 1065-1068. 110, 237-242. Ragka, K., Helcl, J., Jezek, J., Kubelka, Z., Litov, M., Novak, Gust, I. D., Lehmann, N. I., Lucas, C. R., Ferris, A. A. and K., Radkovsky, J., Sery, V., Zejdl, J. and Zikmund, V. Locarnini, S. A. (1978). Studies on the epidemiology of (1966). A milk-borne infectious hepatitis epidemic. Journtal hepatitis A in Melbourne. In Viral Hepatitis: A of Hygiene, Epidemiology, Microbiology and Immunology, Contemporary Assessment of Etiology, Epidemiology, 10, 413-428. Pathogenesis and Prevention, eds. Girish, N. V., Cohen, S. Szmuness, W., Dienstag, J. L., Purcell, R H, Harley, E. J., N. and Schmid, R., pp. 105-112. San Francisco: Abacus Stevens, C. E. and Wong, D. C. (1976). Distribution of Press. antibody to hepatitis A antigen in urban adult Gust, I. D., Lewis, F. A. and Lehmann, N. I. (1978). populations. New England Journal of Medicine, 295, Prevalence of antibody to hepatitis A and polioviruses in 755-759. an unimmunized urban population. American Journal of Szmuness, W., Dienstag, J. L., Purcell, R. H., Stevens, C. E., Epidemiology, 107, 54-56. Wong, D. C., Ikram, H., Bar-Shany, S., Beasley, R. P., Hadler, S. C. (1980). Risk factors for the occurrence of Desmyter, J. and Gaon, J. A. (1977). The prevalence of hepatitis A outbreaks in day care centers. In Epidemic antibody to hepatitis A antigen in various parts of the Intelligence Service 29th Annual Conference, pp. 33-34. world: a pilot study. American Journal of Epidemiology, Atlanta, Georgia: Centers for Disease Control. 106, 392-398. Hughes. J. M., Merson, M. H. and Gangarosa, E. J. (1977). Vernon, A. A. (1980). Hepatitis A associated with a day care The safety of eating shellfish. Journal of the American center in Tulsa, 1979. In Epidemic Intelligence Service 29th Medical Association, 237, 1980-1981. Annual Conference. p. 34. Atlanta, Georgia: Centers for Koff, R. S., Grady, G. F., Chalmers, T. C., Mosley, J. W. and Disease Control. Swartz, B. L. (1967). Viral hepatitis in a group of Boston Vilim, V., Pesek, J., Brejcha, O., Zakova, M., Jindr. J. and hospitals: importance of exposure to shellfish in a Pruchova, M. (1977). Viral hepatitis A, water epidemic in a nonepidemic period. The New England Medical Journal, bungalow community. Ceskoslovenska Epidemiologie, 276, 703-710. Mikrobiologie, Immunologie, 26, 46-51. Krugman, S., Giles, J. P. and Hammond, J. (1970). Hepatitis Villarejos, V. M., Provost, P. J., Ittensohn, 0. L., McLean, A. virus: effect of heat on the infectivity and antigenicity ofthe A. and Hilleman, M. R. (1976). Seroepidemiologic MS- 1 and MS-2 strains. Journal of Infectious Diseases, 122, variations of human hepatitis caused by A, B and a 432-436. possible third virus. Proceedings of the Society for Levin, M. (1978). Fish and shellfish associated disease Experimental Biology and Medicine, 152, 524-528. HEPATITIS A VIRUS AND INFECTIOUS HEPATITIS 179 Viswanathan, R. (1957). Infectious hepatitis in Delhi Willcox, M., Brohult, J., Olsson, I. and Bengtsson, E. (1980). (1955-56), acritical study: epidemiology. Indian.lournal of Antibody to hepatitis A virus in Liberians. Transactions of Medical Research, supplementary number, 45, 1-29. the Royal Society of Tropical Medicine and Hygiene, 74, Wankya, B. M., Hansen, D. P., Ngindu, A. M. N., Feinstone, 690. S. F. and Purcell, R. H. (1979). Seroepidemiology of Zuckerman, A. J. and Howard, C. R. (1979). Hepatitis Viruses hepatitis A and B in Kenya. A rural population survey in of Man. London: Academic Press. Machakos District. East African Medical Journal, 56, 134-138. 11 Rotavirus and Viral Gastroenteritis THE AWARENESS THAT VIRUSES play a major role in and recovery occurs within about a week. Mortality the causation of diarrheal disease has been one of the rates are low in hospitalized children in developed outstanding medical advances of recent time. countries but may be considerable among untreated Previously, surveys of diarrheal disease had failed to children in developing countries. Dehydration and determine the causative agent in up to two-thirds of all shock are the most likely terminal processes, and oral cases-no known pathogen could be isolated from the rehydration is as effective in treating viral diarrhea as it stools of these patients. Since 1972, however, several is in treating bacterial diarrhea (Nalin and others different viruses have been identified in stools by 1979). Rotavirus gastroenteritis may occur as a single electronmicroscopy and have been shown to be case, or one episode of an epidemic outbreak. There is associated with diarrheal disease throughout the also a form of continuing infection in some newborn world. Rotaviruses have received the most attention nurseries in which a high proportion of the infants are and have been accepted as a major cause of childhood asymptomatic. gastroenteritis. Occurrence Description of Pathogens and Diseases Rotavirus appears to be almost universally distri- buted in human populations around the world. It has A growing number of different viruses are now been found in the stools of children with diarrhea from associated with diarrheal disease (see table 9-1). Japan and New Zealand in the East, to Canada and Rotaviruses appear to be the most important of these Argentina in the West. It has been identified in tropical and are therefore given greatest attention in this as well as temperate climates, although it may not be chapter. Several reviews of the rotaviruses have been quite such an important etiological agent for diarrhea published (Flewett and Woode 1978; Holmes 1979; in tropical countries as in temperate regions (patho- McNulty 1978; Steinhoff 1980; Yolken and Kapikan genic E. coli may be more dominant in the tropics; see 1979). chapter 13). Identification Infectious agents A number of different viruses may cause gastroen- Acute nonbacterial gastroenteritis has long been teritis, and the disease may vary accordingly. In recognized as a clinical entity. There was epidemiologi- rotavirus gastroenteritis, the onset is generally quite cal evidence of outbreaks of infectious diarrheas in sudden, and vomiting may be the presenting symptom which neither bacterial nor parasitic organisms could or may accompany diarrhea at the start. Vomiting is be found. Volunteer experiments demonstrated that often the dominant feature rather than diarrhea. Fever diarrhea could be transmitted by oral administration is present in many cases. Dehydration frequently of bacteria-free fecal filtrates. A particle of sub-bacterial occurs, but may be more severe in combined infections size, presumably a virus, seemed likely. The develop- with pathogenic Escherichia. coli. There is no ment of techniques to culture enteroviruses and consistent pattern of association between rotavirus adenoviruses from stool samples failed to identify any and pathogenic E. coli. In hospitalized children the organisms that occurred predominantly in patients fever and vomiting usually resolve in the first 5 days, with diarrhea. The application of electronmicroscopy 181 182 ENVIRONMENTAL BIOLOGY & EPIDEMIOLOGY: VIRUSES to diarrheal stool samples was the decisive advance. ADENOVIRUSES. These viruses are found in small The technique was enhanced by ultracentrifugation, numbers in feces of some patients with diarrhea, but antiserum clumping of particles (immuno-electron- occasionally in great numbers (see, for instance, microscopy, IEM), and negative staining. These methods Richmond and others 1979). The evidence that have their limitations because, unless particles adenoviruses can cause diarrhea is circumstantial, and occur in concentration of greater than 106 per gram there is no equivalent animal model. However, their of feces, they may not be detectable. More recent occasional presence in large numbers indicates that techniques for the identification of rotavirus particles they must have replicated in and destroyed cells. from stools include infected cell immunofluorescence, counter-immunoelectrophoresis, radioimmune assay, ASTROVIRUSES. These are particles of 28 nanometers and enzyme-linked immunosorbent assay (ELISA), and in diameter that are roughly spherical with surface the methodology is still rapidly improving. indentations that result in the appearance of a 5- or 6- Any form of examination of the feces may give a pointed star (figure 11-1b). They have been found in the distorted indication of the pathophysiology of feces of normal children and of those with gastro- gastroenteritis, a condition in which the primary lesion enteritis (see, for instance, Kurtz, Lee and Pickering is in the small bowel. The large bowel is distal to the site 1977). There is still no firm evidence that they are of infection and, even in a child, contains some 10 p o bacteria and also many fungi, mycoplasmas, and pathogenc. protozoa. All of these frequently have their own viral infections and may shed particles into the feces. CALICIVIRUSES. These are picornaviruses of appro- Bacteriophages, unless they have tails, may be very ximately 35 nanometers in diameter (figurel -lc) and difficult to distinguish from small spherical human were previously known as fecal viruses in such diverse viruses. The colon and its flora alter the effluent from species as sealions, pigs, and cats. Calicivirus has now the small bowel in a number of ways before it presents been associated with several outbreaks of gastro- enteritis and has also been found in the stools of as fecal material. asymptomatic individuals (Schaffer 1979; Studdert ROTAVIRUSES. These viruses from the stools of 1978). children are morphologically identical to those found in the stools of some calves, piglets, foals, lambs, mice, CORONAVIRUSES. These are well-known agents of and young monkeys with acute diarrhea. The human acute gastroenteritis in piglets and calves. They vary in virus has been transmitted to a number of these shape and size but have a distinctive appearance in animals. The virus particles are spherical, 70 nano- electron micrographs (figure 11-id). Recently they meters in diameter, and made up of double-stranded have been described in feces from young adults in RNA in two distinct capsid layers that on electron- Britain and from children in Canada and Australia. microscopy give the appearance of a wheel, hence the They have been isolated in tissue culture. They are not name rotavirus (figure 11-la). Rotaviruses are now proven human enteric pathogens, although they are a classifiedasagenusofthefamilyReoviridae(seetable9- major cause of the common cold (Clarke, Caul and 1). There are at least two, and possibly four, serotypes Egglestone 1979; McIntosh 1979; Robb and Bond of human rotavirus. 1979). Figure 11-1. Agents of viral gastroenteritis. (a) Rotaviruses under scanning electronmicroscopy. Scale bar = 0.1 micrometers. (Photo: J. Cohen, Station de Recherches de Virologie et d'Immunologie, Institute National de la Recherche Agronomique, Thiverval, France.) (b) Astroviruses under transmission electronmicroscopy, showing the characteristic 5- or 6-pointed star appearance. Scale bar = 0.1 micrometers. (Photo: C. R. Madeley, Royal Victoria Infirmary, Newcastle-upon-Tyne, UK.) (c) Caliciviruses under transmission electronmicroscopy, showing the characteristic surface hollows. Scale bar = 0.1 micrometers. (Photo: A. J. Zuckerman, London School of Hygiene and Tropical Medicine, London, UK.) (d) Coronaviruses under transmission electronmicroscopy. The virus particles vary in shape and size and possess a distinctive array of widely spaced surface projections, approximately 20 nanometers long, which give the characteristic "corona" appearance. Scale bar = 0.1 micrometers. (Photo: E. 0. Caul, Public Health Laboratory Service, Bristol, UK.) (e) Norwalk agent particles under transmission electronmicroscopy. Scale bar = 0.1 micrometers. (Photo: E. 0. Caul, Public Health Laboratory Service, Bristol, UK) ROTAVIRUS AND VIRAL GASTROENTERITIS 183 s _ ~ ~~~~ - ;-S '~~~~~~~~~ 'I' _rSv 'S 1*1 Nso--i~ ~~d 184 ENVIRONMENTAL BIOLOGY & EPIDEMIOLOGY: VIRUSES ENTEROVIRUSES. Most studies have indicated that containing cockles (Appleton and Pereira 1977). IEM the occurrence of these viruses is no more common in suggests this agent (cockle virus) is antigenically the stools of children with diarrhea than in those from similar to W agent. but different from Norwalk agent. control groups. However, in one outbreak of There is still considerable confusion in identifying gastroenteritis, believed to be due to a failure of water viruses in feces, especially when variations in methods, supply purification, coxsackie- and echoviruses were possible artifacts, and the presence of bacteriophages found as frequently as Shigella sonnei in the stools of are considered. It is far from proven that all the viruses those with diarrhea (Green and others 1968). discussed above cause gastroenteritis, and all have been isolated from healthy persons as well as from MEASLES VIRUS. In temperate climates measles is those with gastroenteritis. On some occasions, more now an exanthem which affects children primarily with than one virus has been present. However, it appears respiratory symptoms and a systemic upset. In the past, likely that, just as the upper respiratory tract reacts to a however, diarrhea was associated with measles and 28 range of viruses by producing the symptoms of the percent of children with measles in a London clinic in common cold, the alimentary tract will react to a range 1904 had diarrhea (Balme 1904). In tropical countries of viruses by developing gastroenteritis. It is only the where measles is frequently more severe, not only is the rotaviruses that are unquestionably a major cause of rash very prominent, but there is evidence of invasion gastroenteritis worldwide, and it is these which are of the bowel epithelium. The giant cells associated with discussed in the rest of this chapter. measles have been seen in the mucosa of biopsy specimens, and the excretion of giant cells in the feces Resoir may be prolonged. Diarrhea is frequently associated servos with measles in the tropics. A study in Guatemala Man is probably the only important reservoir for showed that half of the children under 5 years old with human rotavirus infection. measles had acute diarrhea (Scrimshaw and others 1966). Transmissioni NORWALK AGENT AND OTHER SMALL ROUND It is probable that transmission modes are similar to VIRUSES. Norwalk agent is a small round virus particle those of the enteroviruses and hepatitis A virus; that is, of 27 nanometers in diameter (figure 1 1-le) that caused fecal-oral and usually person-to-person but sometimes an outbreak of nonbacterial gastroenteritis in 50 via contaminated water, food, or shellfish. Airborne percent of students and staff of an elementary school in respiratory transmission remains an additional possi- Norwalk, Ohio (USA) in 1968. There was a 32 percent bility. attack rate among family contacts. Rectal swab filtrates produced disease in volunteers, and sub- sequently the particle was visualized by IEM. Other Incubation period morphologically similar viruses (Montgomery County Studies that include information about more than agent and Hawaii agent) have been isolated from one case of rotavirus diarrhea within a family or closed different epidemics of diarrhea (Dolin 1979). Some of community indicate that the incubation period is these show a cross-immunity, but several distinct between 24 and 72 hours. serotypes have been demonstrated. These agents produce a mild, self-limited gastroenteritis that lasts Period of communicabilitv 24-48 hours and affects older children and adults more often than the rotavirus. This is very uncertain because many details about Particles of similar size have been associated with the route and mode of spread are unknown. Moreover, small epidemics of winter vomiting disease in Britain: rotavirus diarrhea apparently disappears from a the W and Ditchling agents. These particles differ community for months at a time in hot weather; antigenically from the Norwalk agent and a high also, the organism cannot be found in stools unless it is proportion of adults appear to have antibody against present in high concentrations (> 106 per gram). If them. Some patients continued to excrete the particles transmission is dependent on the ingestion of a large for over 2 months after the illness. Smaller spherical number of virus particles, communicability from a particles of 25-26 nanometers were recently found in patient will be at its maximum on about the third to the feces of a high proportion of patients suffering from fourth day of the disease, coinciding with the period of food poisoning in Britain after eating seafood cocktails maximum virus shedding (101l per gram or more) and ROTAVIRUS AND VIRAL GASTROENTERITIS 185 would be unlikely after the eighth day-although By 18 months of age 85 percent of children in the excretion of rotavirus can continue for more than 20 area of Washington, DC (USA) have acquired days. Asymptomatic infection and excretion certainly antibodies to both Type 1 and Type 2 rotaviruses, and occur, but persistent carriage has not been the high antibody prevalence is maintained through- demonstrated. out life (Yolken and others 1978a). In contrast, in the same area, only about 10 percent of 3 year old children Resistance have Norwalk agent antibodies, and this prevalence rises to only around 50 percent later in life (Kapikian Facts are limited by ignorance about the epi- and others 1978). The same picture of rapid acquisition demiology and pathophysiology of rotavirus infection. of rotavirus antibodies by nearly all children, Newborn babies are apparently susceptible to the contrasted with gradual acquistion of Norwalk agent infection, particularly in the nursery situation, but antibodies (to a maximum prevalence of only 33 only a proportion of them develop clinical symptoms. percent), was found in Bangladesh (Kapikian and The low pathogenicity at this age may possibly be due others 1978; Sack and others 1980). to passively acquired maternal immunoglobulins. In temperate countries there is a striking seasonal Although the majority of older children and adults variation, with most cases occurring in the coldest have antibody to rotavirus, adults can be infected as months of the year, whereas in tropical climates (and is shown by rising antibody titers and sometimes by poorer communities) there appears to be much less clinical infections. The existence of at least two seasonal variation. At a children's hospital in rotavirus serotypes that are not cross-protective may Washington, DC (USA) during 1974-78. rotavirus partly explain repeat attacks. accounted for 39 percent of inpatient diarrhea and 22 percent of outpatient diarrhea. The equivalent figures Epidemiology in January were 71 percent and 62 percent, whereas during June and July they were 4.4 percent and 4.8 Rotavirus gastroenteritis is primarily a disease of percent for inpatients and outpatients, respectively children, especially those between 6 months and 3 (Brandt and others 1979). A comparative study in years old. Rotavirus infection can spread very rapidly Dallas (Texas, USA) and San Jose (Costa Rica) among neonates in nurseries, but many of these showed that in both settings rotavirus accounted for infections are asymptomatic (Jesudoss and others 50-60 percent of acute nonbacterial pediatric gastro- 1979). Rotavirus infection has been recorded in adults, enteritis episodes occurring from December through often in association with infection of their children (for February. This is the cool period in Dallas and the dry instance. Wenman and others 1979: Zissis and others season in San Jose. During the rest of the year the virus 1976). In all age groups asymptomatic infection is fairly was not recovered from any Dallas patients but was common, but persistent carriage is not demonstrated. found in 30-40 percent of Costa Rican patients in every Seroepidemiological surveys show that neonates month except May (Hieber and others 1978). have a high prevalence of rotavirus antibodies In developed and temperate countries (such as (presumably of maternal origin) that falls over the first Australia, Britain, Japan, and the USA), about half of 6 months of life. Antibody prevalence then rises again all diarrhea in children that requires hospitalization is until, by about 3 years, 80-90 percent have rotavirus caused by rotavirus infection. During the summer, antibodies, and this high prevalence is maintained 0-20 percent of cases are rotavirus associated, and in thoughout adult life. For instance, a survey of 266 winter this figure rises to 70-80 percent. Studies in children in Vellore (India) showed that the antibody developing and tropical countries have indicated that prevalence was 75 percent among neonates, 30 percent rotavirus accounts for a somewhat lower proportion of among 5-6 month old infants, and 87 percent among 3 hospitalized childhood diarrhea cases-maybe 25-50 year olds (Jesudoss and others 1978). Similar results percent. are found in affluent communities, indicating that Schnagl, Holmes and Mackay-Scollay (1978) rotavirus transmits successfully even in conditions of studied 537 episodes of diarrhea among 473 hospita- good hygiene, pure water, and full sewerage. This lized children under 6 years old in Western Australia. suggests direct person-to-person, fecal-oral, or re- Among aboriginal children the percentages of 387 spiratory routes of transmission, particularly within diarrheal stools from which known pathogens could be family groups. Parent-to-child, child-to-parent, and isolated were: parasites 17 percent, rotavirus 16 sibling-to-sibling spread are all likely (see, for instance, percent, Salmonella or Shigella 13 percent, pathogenic Wyn-Jones, Lillington and Alzaka 1978). E. coli 9 percent, adenovirus 3 percent, and astrovirus 2 186 ENVIRONMENTAL BIOLOGY & EPIDEMIOLOGY: VIRUSES percent. Among nonaboriginal children the per- infants and children with diarrhea at 3 hospitals in centages of 150 diarrheal stools from which known Kenya. Rotavirus accounted for 41 percent of pathogens could be isolated were: rotavirus 25 percent, inpatients in Nairobi, for 14 percent of inpatients and parasites 1 percent, Salmonella or Shigella 10 percent, 17 percent of outpatients in Mombasa, and for 29 pathogenic E. coli 10 percent, adenovirus 4 percent, percent of inpatients and 11 percent of outpatients in and astrovirus 3 percent. The data suggest the Kisumu (see also Mutanda 1980b; Mutanda, possibility of a winter peak of rotavirus gastroenteritis Cruickshank and Itotia 1979). Hansen and others among nonaboriginals and a summer peak among (1978) found that 6 percent of adult inpatients with aboriginals. Rotavirus was detected in the stools of diarrhea in Nairobi had serological evidence of only 2 out of 170 children without diarrhea. rotavirus infectiofi, whereas 26 percent had Shigella Black and others (1979) investigated 4,498 diarrhea and 18 percent had enterotoxigenic E. coli. cases reporting to Matlab hospital (Bangladesh) and Some studies have found that rotavirus infection is were able to identify a pathogen in the stools of 85 associatedwithdiarrheaofmorethanaverageseverity; percent (see table 13-1). Rotavirus was associated with if this is the case, the proportion of hospitalized 23 percent of all reported diarrhea cases and with 40 diarrhea cases due to rotavirus may be greater than the percent of diarrhea cases under 5 years old. proportion of all diarrhea cases. Two community During January-June 1976, Echeverria and others studies support this hypothesis. Spencer and others (1978) studied 82 hospitalized infants and children (1980) isolated rotavirus from only 7 percent (5 of 74) with diarrhea in Manila (Philippines). A viral etiology of nonhospitalized children under 4 years old with was indicated in 17 percent of cases, enterotoxigenic E. diarrhea in a coastal area of El Salvador. Similarly, coli in 11 percent, Salmonella or Shigella in 7 percent, rotavirus accounted for only 14 percent (26 of 183) of Vibrio cholerae in 4 percent, Giardia lamblia in 5 diarrheal episodes, from which no bacterial or percent, and Entamoeba histolytica in 2 percent. Ten protozoal pathogen could be isolated, among 0-3 year percent of children had evidence of infection with more old nonhospitalized children in a highland village in than one enteric pathogen. Only 1 out of 49 healthy Guatemala (Wyatt and others 1979). If all diarrhea children had rotavirus particles in their stools. among these children is considered, the proportion due Echeverria and others (1977) found evidence of to rotavirus was approximately 7 percent. The rotavirus infection in 56 percent (42/75) of children (3 incidence of rotavirus diarrhea was estimated at only days to 4 years old) with diarrhea seen at hospitals in 1.1 episode per child during the first 3 years of life. Taipei (Taiwan) during the summer. Studies of 293 hospitalized children under 5 years old with diarrhea in Caracas (Venezuela) showed a Control Measures rotavirus etiology in 41 percent of cases (Viera de Torres, Mazzali de Ilja and Esparza 1978). Only 3 out The spread of infection may be reduced by improved of 66 healthy children were excreting rotavirus. Espejo personal and domestic hygiene and by the sanitary and others (1978) studied 242 children under 5 years disposal of excreta, but this is uncertain. The very high old with acute diarrhea in two hospitals in Mexico City prevalence of antibodies to rotavirus in children over 2 (Mexico) and found rotavirus excretion in 25 percent. years old in affluent communities indicates that Although the peak of all diarrhea cases in Mexico rotavirus transmits successfully even in conditions of occurred in June-September, the peak of rotavirus near optimum hygiene, water supply, and sanitary diarrhea occurred in October. The highest age-specific facilities. proportions of diarrhea cases with rotavirus excretion Infections by rotavirus in breast-fed infants are less were in the 4-10 month age group. Of the 60 children likely and less severe than in bottle-fed infants. Breast who excreted rotavirus, 22 also excreted Salmonella, milk has been shown to contain specific antibodies to Shigella, or potentially pathogenic serotypes of E. coli. rotavirus (Yolken and others 1978a), but it now Rotavirus infection was less common among breastfed appears that other unidentified properties of breast infants with diarrhea (10 percent) than among milk are responsible for its protective effect (Totterdell, nonbreastfed infants with diarrhea (27 percent). Chrystie and Banatvala 1980). Little information is yet available on rotavirus The development of rotavirus vaccines is a distinct gastroenteritis in Africa. Brookfield and others (1979) possibility within the next few years, but delivering detected rotavirus in the stools of 31 percent of 123 them to the most vulnerable individuals (children aged hospitalized children under 4 years with diarrhea in 5-24 months) will be a difficult task in most developing Dar es Salaam (Tanzania). Mutanda (1980a) studied countries. ROTAVIRUS AND VIRAL GASTROENTERITIS 187 Occurrence and Survival in the a common history of eating seafood cocktails Environment containing cockles grown in waters polluted by scwage (Appleton and Pereira 1977). There is no direct evidence on the behavior or Dismukes and others (1969) reported 33 cases of occurrence of human rotavirus in the environment gastroenteritis of unknown etiology, and 4 cases of because the virus cannot be routinely isolated from hepatitis, occurring among 128 persons attending a environmental samples. Tissue culture methods have picnic at which raw clams were eaten. Ironically, at an been developed (Wyatt and others 1980), but rotavirus annual convention of a shellfish sanitation association does not grow readily in cell culture, and de- held at New Haven (Connecticut, USA) in November monstration of cytopathic effects is difficult. 1968, 19 persons ate raw clams and 17 of them Investigations into rotaviruses in the environment developed acute gastroenteritis of unknown etiology must await the development of improved tissue culture (Ratzan and others 1969). There was subsequently a 37 techniques or sensitive immunological antigen- percent secondary attack rate among family contacts detecting techniques. of the 17. The available evidence on human rotavirus in the The largest outbreak of viral gastroenteritis so far environment is indirect. The knowledge that rotavirus reported occurred in Australia during June and July may be excreted in large numbers (10" per gram) by 1978 (Murphy and others 1979). At least 2,000 cases infected individuals, and that incidence of infection were reported throughout the country; cases had a appears to be very high in some communities, leads to common history of eating rock oysters harvested from the assumption that human rotavirus may be present polluted estuaries near Sydney. The causative or- where fecal pollution is present, especially where high ganism was shown to be Norwalk agent. As a result of concentrations of enteroviruses are found (see chapter this outbreak, the New South Wales state government 9). However, far too little is known about the has required that all oysters harvested from the prevalence of rotavirus excretion, or about the incriminated areas be depurated for at least 2 days in numbers of viruses excreted by asymptomatic ex- disinfected water, and a panel of volunteers has been set creters, to predict at what concentration human up to test-consume samples of oysters prior to rotaviruses might be found in, for instance, sewage. marketing. The data reviewed in chapter 9 on the Some evidence is provided by outbreaks of gastro- elimination of enteroviruses from oysters in sterilized enteritis believed to be of viral etiology that have been water suggest that a 2-day depuration time is traced by epidemiological analysis to a particular inadequate to remove the risk of viral contamination source, such as contaminated water or shellfish. with reliability. Many outbreaks of gastroenteritis have been linked Little is known about the survival of human to polluted water, and many of these have had an rotavirus in the environment, and it is reasonable to undetermined etiology and could be of viral origin. assume, for the time being, that its environmental Craun (1978) reported that during 1975 and 1976 an behavior is similar to that of the enteroviruses (chapter etiological agent could not be identified in 75 percent of 9). Simian rotaviruses and reoviruses may provide a waterborne gastroenteritis outbreaks in the USA. closer model for human rotavirus in the environment From observations of the symptoms, it is more than than the enteroviruses, and recently data on simian probable that some of these outbreaks were due to rotaviruses in water have been reported. Hurst and rotaviruses or other diarrhea-causing viruses. Gerba (1980) compared the survival of poliovirus 1, However, there is no evidence that water conforming to echovirus 7, coxsackievirus B3, and simian rotavirus in conventional bacteriological criteria has ever caused clean and polluted freshwaters and in estuarine waters rotavirus infection, and waterborne gastroenteritis of various salinities (1.2-2.8 percent) at 20°C. All occurs in circumstances similar to those which may viruses survived for a very similar time, undergoing a 3 lead to other outbreaks of waterborne, fecal-oral log reduction in concentration in 6 to over 14 days gastroenteritis (see, for instance, Morens and others in freshwaters and in 2 to 3 days in estuarine waters. 1979). This preliminary experiment suggests that simian Other sources of circumstantial evidence of ro- rotavirus in fresh and saline water exhibits death rates tavirus behavior in the environment are the documen- well within the range reported for enteroviruses. ted accounts of gastroenteritis associated with the Rotavirus is very stable under some conditions. The ingestion of contaminated shellfish. The so-called virus is stable in the pH range 2-9.8 and survives for at cockle virus was detected during outbreaks of least 7 months, but not 4 years, at 18-20°C. Rotavirus gastroenteritis in the UK affecting 797 people who had in feces remained infectious and virulent for calves after 188 ENVIRONMENTAL BIOLOGY & EPIDEMIOLOGY: VIRUSES 5 years storage at 4°C. Preliminary studies indicate Inactivation by Night Soil and Sludge that rotavirus may resist a temperature of 60'C, but not Treatment Processes 63°C, for 30 minutes (G. N. Woode, personal communication). As with sewage treatment processes, no direct evidence is available on the inactivation of human rotavirus by night soil or sludge treatment. As noted above, reoviruses may provide a suitable model for Inactivation by Sewage Treatment environmental studies on human rotaviruses, and Processes several differences in the environmental characteris- tics of enteroviruses and reovirus are known to exist. The lack of adequate detection techniques has For instance, a series of studies by Ward and Ashley prevented any direct studies on the inactivation of (1976, 1977a, 1977b, 1977c, 1978) have shown that human rotavirus by sewage treatment. However, there reovirus is more heat resistant than poliovirus but that, is some indication that rotaviruses may be less unlike poliovirus, it is not protected against heat inactivated in treatment systems than polioviruses. inactivation by being in sludge. These studies also Farrah and others (1978) compared the ability of showed that ammonia, although it is highly virucidal poliovirus, human rotavirus and simian rotavirus to to enteroviruses at pH above 8, does not affect adsorb to aluminum hydroxide flocs and activated reoviruses, and that some detergents sensitize reovirus sludge flocs. Aluminum hydroxide flocs reduced the to heat inactivation while they protect poliovirus. concentration of poliovirus in tap water by 3 log units but only reduced the concentration of simian rotavirus by 1 log unit or less and did not noticeably reduce the Literature Cited number of rotavirus particles present in a dilute stool suspension. Activated sludge flocs reduced the concentraion. ofvaded pliudgefls byd07 et 1.h Appleton, H. and Pereira, M. S. (1977). A possible virus concentratio of added poliovirus by 07to log aetiology in outbreaks of food-poisoning from cockles. units but reduced simian rotavirus numbers by 0.5 log Lancet, 1, 780-781. units or less. This suggests that the adsorptive Balme, H. (1904). The signs and symptoms of measles in characteristics of poliovirus and rotavirus are different relation to diagnosis and prognosis. Practitioner, 1, and that lesser removals of rotavirus occur during 504-506. water coagulation or activated sludge treatment than Black, R. E., Merson, M. H., Rowe. B., Taylor, P. R., Mizanur have been reported for polioviruses (see chapter 9). Rahman, A. S. M., Azizal Huq, M., Abdul Aleem, A. R. M., Goyal and Gerba (1979) compared the proportion Sack, D. A. and Curlin, G. T. (1979). Epidemiology of of 27 different excreted viruses that were adsorbed to a enterotoxigenic Escherichia coli in rural Bangladesh. In sandy loam soil when shaken in water for 30 minutes. Proceedings of the 14th Joint Conferences US-Japan Between 91 and 99.99 percent of all viruses adsorbed to Cooperatite Medical Science Program. Cholera Panel, the soil, except for echovirus 1 (55 percent), echovirus Symposium on Cholera, eds. Takeya, K. and Zinnaka, Y., 12 (78 percent), echovirus 29 (14 percent), and simian pp 292-301. Tokyo: Toho University. Brandt, C. D., Kim, H. W., Yolken, R. H., Kapikian, A. Z., rotavirus (52 percent ). However, in another series of Arrobio, J. O., Rodriguez, W. J.. Wyatt, R. G., Chanock. R. adsorption experiments using nine different soils, M. and Parrott, R. H. (1979). Comparative epidemiology simian rotavirus tended to adsorb more than all other of two rotavirus serotypes and other viral agents asociated viruses studied except poliovirus 1, echovirus 7, and with pediatric gastroenteritis. Americani Journal of bacteriophage T4. A considerable amount of ad- Epidemiology, 110, 243-254. ditional experimentation will be required before it is Brookfield, D. S. K., Cosgrove, B. P.. Bell, E. J. and Madeley, clear whether rotaviruses are less readily adsorbed C. R. (1979). Viruses demonstrated in children in than enteroviruses or merely less readily adsorbed than Tanzania; studies in diarrhoea and measles. Jou7nal of poliovirus 1. Injection, 1, 249-255. The next few years will undoubtedly see many Clarke, S. K. R., Caul, E. 0. and Egglestone, S. I. (1979). The The next ~~~~~~~~~~human enteric coronaviruses. Postgradluate Medlical investigations into the removal of rotavirus from humn 55, 135 142. sewage and water. Pending the development of Journal, 55, 135-142. Craun, G. F. (1978). Disease outbreaks caused by drinking adequate concentration and detection techniques for water. Journal of the Water Pollutioni Control Federation, human rotaviruses, studies may be done using seeded 50, 1362-1374. simian rotaviruses and reoviruses, which may provide Dismukes, W. E.. Bisno. A. L., Katz, S. and Johnson, R. F. suitable models for human rotavirus. (1969). An outbreak of gastroenteritis and infectious ROTAVIRUS AND VIRAL GASTROENTERITIS 189 hepatitis attributed to raw clams. American1 Journal oj Kapikian, A. Z., Greenberg, H. B., Cline, W. L., Kalica, A. R., Epidemiology, 89, 555-561. Wyatt, R. G., James, H. D., Lloyd, N. L., Chanock, R. M., Dolin, R. (1979). Norwalk-like agents of gastroenteritis. In Ryder, R. W. and Kim, H. W. (1978). Prevalence of Principles anddPractice of Infectious Diseases, eds. Mandell, antibody to the Norwalk agent by a newly developed G. L., Douglas, R. G. and Bennett, J. E., pp. 1364-1370. immune adherence hemagglutination assay. Journal of New York: John Wiley. Medical Vo. i4. .: , 2, 281-294. Echeverria, P., Blacklow, N. R., Vollet, J. L., Ulyangco, C. V., Kurtz, J. B., Lee, T. W. and Pickering, D. (1977). Astrovirus Cukor, G., Soriano, V. B., DuPont, H. L., Cross, J. H., associated gastroenteritis in a children's ward. Journal oj Orskov, F. and 0rskov, I. (1978). Reovirus-like agent and Clinical Pi. l. .1. i, 30, 948-952. enterotoxigenic Escherichia coli infections in pediatric McIntosh, K. (1979). Coronavirus. In Principles and Practice diarrhea in the Philippines. Journal of Infectious Diseases, of Infectious Diseases, eds. Mandell, G. L., Douglas, R. G. 138, 326-332. and Bennett, J. E., pp. 1212-1217. New York: John Wiley. Echeverria, P., Ho, M. T., Blacklow, N. R., Quinnan, G., McNulty, M. S. (1978). Rotaviruses. Journal of General Portnoy, B., Olson, J. G., Conklin, R., DuPont, H. L. and Virology, 40, 1-18. Cross, J. H. (1977). Relative importance of viruses and Morens, D. M., Zweighaft, R. M., Vernon, T. M., Gary, G. W., bacteria in the etiology of pediatric diarrhea in Taiwan. Eslien, J. J., Wood, B. T., Holman, R. C. and Dolin, R. Journal of Infectious Diseases, 136, 383-390. (1979). A waterborne outbreak of gastroenteritis with Espejo, R. T., Calder6n, E., Gonzalez, N., Salom6n, A., secondary person-to-person spread. Lancet, 1, 964-966. Martuscelli, A. and Romero, P. (1978). Rotavirus Murphy, A. M., Grohmann, G. S., Christopher, P. J., Lopez, gastroenteritis in hospitalized infants and young children W. A., Davey, G. R. and Millsom, R. H. (1979). An in Mexico City. Revista Latinamericano de Micraobiologia, Australia-wide outbreak of gastroenteritis from oysters 20, 239-246. caused by Norwalk virus. Medical Journal of Australia, 2, Farrah, S. R., Goyal, S. M., Gerba, C. P., Conklin, R. H. and 329-333. Smith, E. M. (1978). Comparison between adsorption of Mutanda, L. N. (1980a). Epidemiology of acute gastro- poliovirus and rotavirus by aluminum hydroxide and enteritis in early childhood in Kenya. III. Distribution of activated sludge flocs. Applied and Environmental the aetiological agents. East African Medical Journal, 57, Microbiology, 35, 360-363. 317-326. Flewett, T. H. and Woode, G. N. (1978). The rotaviruses. (1980b). Epidemiology of acute gastroenteritis in Archives of lV. . i. ., . 57, 1-23. early childhood in Kenya. IV. Some clinical and Goyal, S. M. and Gerba, C. P. (1979). Comparative laboratory characteristics relative to the aetiological adsorption of human enteroviruses, simian rotavirus and agents. East Ajiican Medical Journal, 57, 599-606. selected bacteriophages to soils. Applied and Mutanda, L. N., Cruickshank, B. and Itotia, J. N. (1979). Environmental Microbiology, 38, 241-247. Rotavirus infection in private practice in Nairobi City. Green, D. M., Scott, S. S., Mowat, D. A. E., Shearer, E. J. M. East African Medical Journal, 56, 589-592. and MacFarlane Thomson, J. (1968). Water-borne Nalin, D. R., Levine, M. M., Mata, L., de Cespedes. C., outbreak of viral gastroenteritis and Sonne dysentery. Vargas, W., Lizano, C., Loria, A. R., Simhon, A. and Mohs, Journal of Hygiene, 66, 383-392. E. (1979). Oral rehydration and maintenance of children Hansen, D. P., Kaminsky, R. G., Bagg, R., Kapikian, A. Z., with rotavirus and bacterial diarrhoeas. Bulletin of the Slack, R. C. B. and Sack, D. A. (1978). New and old agents World Health Organization, 57, 453-459. in diarrhea: a prospective study of an indigenous adult Ratzan, K. R., Bryan, J. A., Krackow, J., Meyer, G. and African population. American Journal of Tropical Medicine Larson, C. D. (1969). An outbreak of gastroenteritis and Hygiene, 27, 609-615. associated with ingestion of raw clams. Journal of Hieber, J. P., Shelton, S., Nelson, J. D., Leon, J. and Mohs, E. Infectious Diseases, 120, 265-268. (1978). Comparison of human rotavirus disease in tropical Richmond, S. J., Caul, E. O., Dunn, S. M., Ashley, C. R., and temperate settings. American Journal of Diseases of Clarke, S. K. R. and Seymour, N. R. (1979). An outbreak of Children, 132, 853-858. gastroenteritis in young children caused by adenoviruses. Holmes, 1. H. (1979). Viral gastroenteritis. Progress in Lancet, 1, 1178-1180. Medical Virology, 25, 1-36. Robb, J. A. and Bond, C. W. (1979). Coronaviridae. In Hurst, C. J. and Gerba, C. P. (1980). Stability of simian Comprehensive Virology, 14, eds. Fraenkel-Conrat, H. rotavirus in fresh and estuarine water. Applied and and Wagner, R. R., pp. 193-247. New York: Plenum. Environmental Microbiology, 39, 1-5. Sack, D. A., Gilman, R. H., Kapikian, A. Z. and Aziz, K. M. S. Jesudoss, E. S., John, T. J., Maiya, P. P., Jadhav, M. and (1980). Seroepidemiology of rotavirus infection in rural Spence, L. (1979). Prevalence of rotavirus infection in Bangladesh. Journal ofClinical Microbiology, 11,530-532. neonates. IndianJournalofMedical Research, 70,863-867. Schaffer, F. L. (1979). Caliciviruses. In Comprehensive Jesudoss, E. S.,John,T. J., Mathan, M. and Spence, L. (1978). i,,.1. .,, 14, eds. Fraenkel-Conrat. H. and Wagner, R. Prevalence of rotavirus antibody in infants and children. R., pp. 249-284. New York: Plenum. Indian Journal of Medical Research, 68, 383-386. Schnagl, R. D., Holmes, I. H. and Mackay-Scollay, E. M. 190 ENVIRONMENTAL BIOLOGY & EPIDEMIOLOGY: VIRUSES (1978). A survey of rotavirus associated with gastro- dewatered wastewater sludge. Applied and Enuironmenital enteritis in aboriginal children in Western Australia. Microbiology, 36, 898-905. Medical Journal of Australia, 1, 304-307. Wenman, W. M., Hinde, D., Feltham, S. and Gurwith, M. Scrimshaw, N. S., Salomon,J. B., Bruch, H. A. and Gordon, J. (1979). Rotavirus infection in adults: results of a E. (1966). Studies of diarrheal disease in Central America. prospective family study. New England Journal oj VIII. Measles: diarrhea and nutritional deficiency in rural Medicine, 301, 303-306. Guatemala. American Journial of Tropical Medicinie and Wyatt, R. G., James, W. D., Bohl, E. H., Theil, K. W., Saif, L. 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Applied and Environmental antibody directed against rotavirus in human milk, Microbiology, 31, 921-930. measurement by means of enzyme-linked immunosorbent (1977a). Identification of the virucidal agent in assay. Journal of Pediatrics, 93, 916-921. wastewater sludge. Applied and Environmenital Yolken, R. H., Wyatt, R. G., Zissis, G., Brandt, C. D., Microbiology. 33, 860-864. Rodriguez, W. J., Kim, H. W., Parrott, R. H., Urrutia, J. J., (1977b). Inactivation of enteric viruses in wastewater Mata, L., Greenberg, H. B., Kapikian, A. Z. and Chanock, sludge through dewatering by evaporation. Applied and R. M. (1978b). Epidemiology of human rotavirus types 1 Environmental Microbiology, 34, 564-570. and 2 as studied by enzyme-linked immunosorbent assay. (1977c). Discovery of an agent in wastewater sludge New England Journal of Medicine, 299, 1156-1161. that reduces the heat required to inactivate reoviruses. Zissis, G., Lambert, J. P., Fonteyne, J. and de Kegel, D. D. Applied and Environmental Microbiology, 34, 681-688. (1976). Child-mother transmission of rotavirus. Lancet, 1, - (1978). Heat inactivation of eniteric viruses in 96. SECTION II Excreted Bacteria Chapter 12 Campylobacter and Campylobacter Enteritis 13 Pathogenic and Nonpathogenic Escherichia coli and'other Bacterial Indicators of Fecal Pollution 14 Leptospira and Leptospirosis 15 Salmonella, Enteric Fevers, and Salmonelloses 16 Shigella and Shigellosis 17 Vibrio cholerae and Cholera 18 Yersinia and Yersiniosis 12 Campylobacter and Campylobacter Enteritis THREE CHAPTERS of this book describe recently Identification recognized causes of diarrhea that are now believed to . . be of major importance throughout the world. These Campylobacter enterits (also called campylo- are the rotaviruses and other viruses (chapter 11); the bacter etei infecion cue by various pathogenic forms of Escherichia coli (chapter 13and some bacteria of the genus Campylobacter, sequences of the infection vary from asymptomatic 1; . . . ' excretion or mild symptoms to severe disease. In some which are described in this chapter. Knowledge of Campylobacter as a cause of diarrhea in man is recent affected patients the diarrhea is profuse and watery and .. . . . ...............is often accompanied by strong abdominal pain, and limited. The first isolations of the organism from isotnacmnedb srngboialpn' andolimited. T f isolathiosfhea oanism from headache, and fever. Dysenteric stools containing blood Australia (Cooper and Slee 1971) and in 1972 in and mucus are fairly common, especially in children. Austalgia (Cooper and othees 1971) and ins 197 n Vomiting is uncommon. Illness usually persists for a few Belgium (Dekeyser and others 1972). It was only husofwasbtnoeainstacniu durig 197 tat te sale f th prblembecme cear hours to a few days, but in some patients it may continue during 1977 that the scale of the problem became clear frwes eyrto n lcrlt elcmn r in Europe; information on Cam.pylobacter enteritis . for weeks. Rehydration and electrolyte replacement are the USA is even more recent. Very little is yet known sometimes required. Antibiotic therapy is usually about this infection in the developing countries. . . . ' . i . Several comprehensive reviews have been published proven. Complications include an abdominal pain of since 1977 (Butzler 1978, Butzler and Skirrow 1979. such intensity that acute peritonitis is diagnosed and Karmali and Fleming 1979; Skirrow 1977; Smibert surgery often undertaken. Reactive arthritis has been 1978). reported as a complication of Campylobacter enteritis in 2 percent (8 of 340) of cases in Finland (Kosunen and others 1980). Description of Pathogen and Disease Occurrence The delayed recognition of the important role of The exact distribution and importance of Campylobacter as a cause of diarrhea is due to the Campylobacter enteritis in various geographical problems of isolating these bacteria. As strict aerobes regions arenot yet known. It isvery probable, however, growing under low oxygen levels, they will not grow that C. fetus ssp. jejuni is a major cause of diarrhea under the aerobic or anaerobic growth conditions throughout the world (table 12-1). used in most laboratories; furthermore, unless selective growth systems are used they are overgrown by other bacteria present in feces. Now that these difficulties have been overcome, it seems that campylobacters are the single most common bacterial Campylobacters are microaerophilic, Gram- cause of diarrhea in several countries (table 12-1). negative, motile, slender (0.2-0.4 micrometers in However, the mechanism by which campylobacters width), curved or spiral bacteria (figure 12-1). They are cause diarrhea remains obscure. Although they are oxidase positive and do not attack sugars. The genus is commonly isolated from fecal specimens, their divisible into two groups on the basis of the catalase significance as pathogens is not always clear. reaction and nitrate reduction test. The organisms 193 194 ENVIRONMENTAL BIOLOGY & EPIDEMIOLOGY:BACTERIA Table 12-1. Prevalence of excretion of Campylobacter and other enteric pathogens by individuals with and without diarrhea in twelve countries Number Prevalenc e Of of excretion persons Prevalence of other with (+) of bacterial or and Campylobacter protozoal without (-) excretion pathogens Country Age group diarrhea (percent) (percent) Source Australia All ages +224 5.8 (5.4)a NDb Steele and McDermott All ages -530 0 ND (1978) Bangladesh All ages +204 12.0 ND Blaser and others (1980a) All ages + 97b 5.2 ND 1-4 years +80 8.6 ND 1-4 years + 34b 5.9 ND 1-5 years -141 18.0 ND Belgium Children + 3200 5.8 ND Butzler (1978) Children -6500 1.7 ND Adults + 600 2.3 ND Adults -700 0.7 ND Brazil 0-12 years +217 6.4 ND Ricciardi and Ferreira (1980) England All ages +280 14.0 (12) 13.0 Bruce, Zochowski and All ages -156 0.6 1.9 Ferguson (1977) All ages + 182 7.6 ND Dale (1977) All ages -60 0.2 ND All ages +-860 4.2 4.4 Pearson and others (1977) All ages +-330 5.8 ND Tanner and All ages -120 0.8 ND Bullin (1977) Indonesia 0-9 years + 150 10.0 ND Rockhill >9 years +200 2.0 ND and others 0-9 years +7c 28.0 ND (1980) >9 years +150l 2.0 ND All ages -ND < 1.0 ND Rwanda Children + 150 11 42 De Mol and Children -58 0 31 Bosmans (1978) Scotland All ages + 196 8.7 (7.1) 16 Tefler Brunton All ages -50 0 0 and Heggie (1977) South Africa 0-8 months +-47 32 (31) 40 Bokkenheuser 0-8 months -45 4 15 and others (1979) 9-24 months +31 39 (38) 39 9-24 months -18 44 50 Spain All ages + 446 4.5 17 Lopez Brea, Molina and Baquero (1979) USA All ages +238 4.6 ND MMWR (1979a) All ages +956 4.1 ND Blaser and All ages -548 0 ND others (1980c) Zaire Children + 70 8.6 (8.6) ND Butzler (1973) Children -30 0 ND ND No data. a. Figures in parentheses refer to Campylobacter isolations in the absence of other known bacterial or protozoal pathogens. b. These patients had dysentry (bloody stools). c. These patients had suspected typhoid. CAMPYLOBACTER AND CAMPYLOBACTER ENTERITIS 195 . 4~~~~~~~~ Figure 12-1. Campylobacter under scanning electronmicroscopy. The polar flagella are clearly seen. Scale bar micrometer. (Photo: J. P. Butzler, H6pital Universitaire Saint Pierre, Brussels, Belgium) considered in this chapte r are catalase positive, countries have implicated domestic animals (especially Although campylobacters have aerobic metabolism, puppies), caged birds, poultry (alive or undercooked), they are unable to grow in atmospheric oxygen. pigs, sheep, and cows as possible sources of human Growth occurs at oxygen concentrations of between 3 infections (Blaser and others 1980c; Bruce, Zochowski and 7 percent. Incubation on isolation media at 430C and Ferguson 1977; Butzler and Skirrow 1979; aids the isolation of C.jetus ssp. jejuni, and incubation MMWR 1978b, 1979a, 1979b; Pearson and others at 250C favors C. fetus ssp. intestinalis and ssp. 1977). The degree to which man is an important venerealis. C. fetus ssp. jejuni has been the most reservoir for human infection is not clear. Most studies commonly described isolate associated with diarrhea, listed in table 12-1 found a very low prevalence (0-1.7 but the significance of other campylobacters has not percent) of Campylobacter excretion among healthy been fully assessed. C. fetus ssp. venerealis causes individuals. By complete contrast, the data from enzootic sterility in cattle and is transmitted venereally. Bangladesh and South Africa (table 12-1) showed that C.jfetus ssp. intestinalis causes abortion in sheep and Campylobacter are excreted by a substantial proportion cattle, is transmitted by the fecal-oral route, and is a of healthy children. The important reservoirs of rare, opportunistic pathogen of man. The taxonomy of Campylobacter in poor communities in developing the catalase-positive campylobacters remains con- countries remain to be elucidated. fused. The organism described here as C. fetus ssp. jejuni is also called C.jejuni, or C.jejuni and C. coli, or, in Transmission the older literature, "related vibrios." Transmission is presumed to be fecal-oral, from the Reservoirs feces of infected people, animals, or birds. Infected persons with diarrhea excrete 106-109 C. fetus ssp. Although it is known that a wide variety of animals jejuni per gram of feces. In affluent communities there is and birds may excrete C.fetus ssp. jejuni, the reservoirs little evidence of direct person-to-person spread, except that are functionally important for human infection among young children in nurseries. In poor com- have not been determined. Studies in developed munities and developing countries it is very probable 196 ENVIRONMENTAL BIOLOGY & EPIDEMIOLOGY:BACTERIA that person-to-person spread is of considerable zoonotic salmonelloses (chapter 15). It is possible that importance, although studies are required to confirm the dominant route of transmission, in developed this. Several reports in developed countries indicate countries, is from infected animals to man, either as a transmission via undercooked poultry (Butzler and result of handling pets or farm animals or as a result of Skirrow 1979; MMWR 1979a) and unpasteurized milk ingesting poorly cooked meat (especially poultry) or (Blaser and others 1979; MMWR 1978b; Robinson and unpasteurized milk. If this is the case, then its others 1979; Taylor, Weinstein and Bryner 1979), and epidemiology in developed countries should indeed be human infection from contact with infected pet animals very similar to the salmonelloses. This interpretation and birds is also suspected (Blaser and others 1978, would also explain why C. fetus ssp. jejuni is such a 1980c; Butzler and Skirrow 1979; MMWR 1979b). The prominent cause of bacterial diarrhea, even in affluent organism can persist in chicken and turkey carcasses communities with high standards of environmental during preparation and refrigeration for commercial sanitation (table 12-1). Reportings of Campylobacter marketing (Simmons and Gibbs 1979). Waterborne enteritis tend to peak during the warm summer months transmission was suspected in one major outbreak in in England and Wales, Belgium. and the USA (Butzler the USA (MMWR 1978a). and Skirrow 1979). Data on infective dose are not yet available, but a The data in table 12-1 show that C.fetus ssp. jejuni medical laboratory technician in Australia successfully has been associated with 4-14 percent of diarrhea cases infected himself by ingesting 106 C. fetus ssp. jejuni in in developed countries. In these same countries, the milk (Steele and McDermott 1978). prevalence of Campylobacter excretion by healthy persons is low (0-1.7 percent). The picture in Incubation period developing countries is unclear. In some (for instance, Indonesia, Rwanda, and Zaire) the prevalences of Incubation periods for Campylobacter enteritis are Campylobacter infection among those with and somewhat longer than is common for other bacterial without diarrhea are similar to the prevalences enteric infections. Recorded or estimated incubation reported from developed countries. In Bangladesh and periods are from 1.5 to ll days, but usually are between South Africa, however, a very different picture has 3 and 5 days. emerged. In Bangladesh, 18 percent of 141 village children (1-5 years old) were excreting Cantiplobacter Period of comnmunicability during the dry season. whereas only 2 percent were excreting Shigella, and none were excreting Salmonella One study in the USA (Blaser and others 1980c) (Blaser and others 1980a). Fifty-two percent (13 of 25) found that fecal carriage of C.fetus ssp. jejuni was for a of these Campylobacter-positive children had had no median period of 15 days from the onset of illness. history of diarrhea in the 30 days prior to specimen Most patients were not excreting the organism after 21 collection. The prevalence of Campylobacter excretion days, and the maximum period of excretion recorded in the 12-23 months age group was 39 percent. was 7 weeks. Jones (1979) reported excretion of the Similarly, in Soweto (South Africa), Bokkenheuser and pathogen for 18-39daysby 12 adult patients employed others (1979) reported a 44 percent prevalence of at a food factory in England. Campylobacter excretion among healthy, black child- ren age 9 to 24 months (see also Koornhof and others Resistance 1979). While it seems certain that C.fetus ssp.jejuni is a cause of some diarrhea in developing countries, the The disease has been described in both children and relative importance of this etiologic agent in com- adults. Circulating antibody can be detected, and it parison with other known major agents (especially may well be that some immunity is conferred by enterotoxigenic E. coli and rotavirus) remains un- infection. determined. Data from England (Butzler and Skirrow 1979; Dale Epidemiology 1977) suggest that the highest incidence of disease occurs among people 5 to 34 years old, whereas some The epidemiology of Campylobacter enteritis is reports from developing countries suggest that infants poorly understood in the developed countries and and young children are the most affected (Blaser and totally obscure in the developing countries. It seems others 1980a; DeMol and Bosmans 1978; Ricciardi clear that it is a zoonosis, and it may be that the nearest and Ferreira 1980). This, in turn, suggests the possible known parallel is with the epidemiology of the importance of person-to-person transmission in CAMPYLOBACTER AND CAMPYLOBACTER ENTERITIS 197 developing countries. However, Blaser and others 25°C. Comparative studies in acid and water showed (1980a) found that Campylobacter infection among that survival was significantly curtailed at pH values of children in a rural area of Bangladesh was not clustered less than 3. A 7 log reduction occurred in 20 minutes at by household and considered that there might be pH 2.4 "relatively little person-to-person transmission." Of peripheral interest are the experiments of An outbreak of Campylobacter enteritis affected Lindenstruth and Ward (1948) with Vibriofetus, which 2,000 out of the 10,000 inhabitants of Bennington might now be classified as Campylobacter fetus ssp. (Vermont, USA) during a 2-week period in May-June intestinalis. They showed that, at 20°C and 37°C, 1978 (MMWR 1978a). All parts of the town were inoculations of 1.5 x 109 organisms survived for 10 involved, and there was no evidence of secondary days but not for 20 days in hay, soil, and sheep manure. person-to-person spread. The town water supply was At 6°C, the same inoculation in the same environments partially chlorinated, but not otherwise treated, and survived for 20 days but not for 30 days. several areas of the town were receiving water with no residual chlorine over the period of the outbreak. No Inactivation by Sewage Treatment Campylobacter was isolated from the water, but the Processes water supply was strongly implicated as the common source of the outbreak. No information is available on the destruction of C. fetus ssp.jejuni by sewage treatment processes or on the Control Measures occurrence of this organism in sewage. Very little can be said with certainty about the Inactivation by Night Soil and Sludge control of Campylobacter enteritis until its epide- Treatment Processes miology is further understood. Hygienic excreta disposal, good personal and domestic cleanliness, No information is available on the destruction of C. adequate cooking of poultry and care in handling pets fetus ssp. jejuni by night soil and sludge treatment and farm animals are all presumed to be important processes or on the occurrence of this organism in protective measures. night soil and sludge. Occurrence and Survival in the Literature Cited Environment Blaser, M.. Cravens, J., Powers, B. W. and Wang, W. L. Although it is known that C. fetus ssp. jejuni is (1978). Campylobacter enteritis associated with canine excreted by a wide variety of animals and birds, almost infection. Lancet, 2, 979-981. no data exist on the presence of these organisms in the Blaser, M. J., Cravens, J., Powers, B. W., LaForce. F. M. and Wang, W. L. (1979). Camnpylobacter enteritis associated environment. Knmll, Suckling and Pearson (1978) wihunatu'zdmik meia.Junl.fMdiie isolated C.fetus ssp.jejuni from 21 percent (7 of 34) of w6th unpasteu1zed milk. Aner8can Journal of Medicine, seawater samples, and from 74 percent (37 of 50) of Blaser, M. J., Glass, R. I., Huq, M. I., Stoll. B., Kibriya. G. M. river and pond samples, in the Southampton area and Alim, A. R. M. A. (1980a). Isolation of Camnpylobacter (UK). All positive water samples also contained E. coli. fetus ssp. jejuni from Bangladeshi children. Journal of Very little is yet known about the survival of C.fetus Clinical Microbiology, 12, 744-747. ssp. jejuni in various environmental habitats. In one Blaser, M. J., Hardesty, H. L., Powers, B. and Wang, W. L. study, C. fetus ssp. jejuni was enumerated in stored (1980b). Survival of Campylobacter fetus subsp. jejuni in feces, urine, water, and milk (Blaser and others 1980b). biological milieus. Journal of Clinical Microbiology, 11, In naturally infected feces, a 7 to 9 log reduction 309-313. occurred in 9 to 22 days at 4°C and in 3 to 8 days at Blaser, M. J., LaForce, F. M., Wilson, N. A. and Wang, W. L. 25.C. In urinehighinitilconentraion(1980c). Reservoirs for human campylobacteriosis. 25°C. In urine, high initial concentrations became Journal of Infectious Diseases, 141, 665-669. undetectable in less than 2 days at 37°C, but organisms Bokkenheuser, V. D., Richardson, N. J., Bryner, J. H., Roux, were viable for up to 35 days at 4°C. In autoclaved D. J., Schutte, A. B., Koornhof, H. J., Freiman, I. and stream water, a 7 log reduction took 5 to 33 days at 4°C Hartman, E. (1979). Detection of enteric campylobac- and 2 to 4 days at 25°C. In pasteurized milk, maximum teriosis in children. Journal of Clinical Microbiology, 9, survival times were 22 days at 4°C and less than 3 days at 227-232. 198 ENVIRONMENTAL BIOLOGY & EPIDEMIOLOGY: BACTERIA Bruce, D., Zochowski, W. and Ferguson, I. R. (1977). (1978b). Campylobacter enteritis-Colorado. Camnpylobacter enteritis. Britishl Medical Journal., 2, 1219. Morbidity and Mortality Weekly Report, 27, 226 and 231. Butzler, J. P. (1973). Related vibrios in Africa. Lancet. 2, 858. - (1979a). Cam pylobacter enteritis-Iowa. Morbidity (1978). Infection with campylobacters. In Modern and Mortality Weekly Report, 28, 565-566. Topics in Infection, ed. Williams, J. D., pp. 214-239. (1979b). Campylobacter enteritis in a household London: Heinemann. Colorado. Morbidity and Mortality Weekly Report, 28, Butzler, J. P. and Skirrow. M. B. (1979). Campylobacter 273-274. enteritis. Clinics in Gastroenterology. 8. 737-765. Pearson, A. D., Suckling, W. G., Ricciardi, I. D., Knill. M. and Cooper, I. A. and Slee, K. J. (1971). Human infection by Ware, E. (1977). Campylobacter-associated diarrhoea in Vibrio fetus. Medical Journal of Australia, 1, 1263-1267. Southampton. British Medical Journal, 2, 955-956. Dale, B. (1977). Campylobacter enteritis. British Medical Ricciardi, I. D. and Ferreira, M. C. S. (1980). The age Journal, 2, 318. distribution in children with Campylobacter enteritis. Dekeyser, P., Gossuin-Detrain, M., Butzler, J. P. and Transactions of the Royal Society of Tropical Medicine and Sternan,J. (1972). Acute enteritis due to relatedvibrio: first Hygiene, 74, 687. positive stool cultures. Journal of'lnfectious Diseases, 125, Robinson, D. A., Edgar, W. J., Gibson, G. L., Matchett, A. A. 390-392. and Robertson, L. (1979). Campylobacter enteritis De Mol, P. and Bosmans, E. (1978). Campylobacter enteritis associated with consumption of unpasteurized milk. in Central Africa. Lancet, 1, 604. British Medical Journal, 1, 1171-1173. Jones, A. (1979). Campylobacter enteritis in a food factory. Rockhill, R. C., Ringerts. S.. Moechtar Muhammad, A. and Lancei, 1, 618-619. Soetomo, A. (1980). Prevalence of Campylobacter fetus Karmali, M. A. and Fleming, P. C. (1979). Campylobacter subsp. jejuni-caused gastroenteritis in some patients in enteritis. Canadian Medical Association Journal, 120, Jakarta, Indonesia. In Abstracts of'the 10th Internzational 1525-1532. Conigress on Tropical Medicine and Malaria, pp. 28-29. Knill, M., Suckling. W. G. and Pearson, A. D. (1978). Manila: Institute of Public Health. University of the Environmental isolation of heat-tolerant Campylobacter in Philippines. the Southampton area. Lancet, 2. 1002-1003. Simmons, N. A. and Gibbs, F. J. (1979). Campylobacter spp. Koornhof, H. J., Robins-Browne, R. M., Richardson, N. J. in oven-ready poultry. Journal of Infection, 1, 159-162. and Cassel, R. (1979). Etiology of infantile enteritis in Skirrow, M. B. (1977). Campjylobacter enteritis: a "new" South Africa. Israel Journal of Medical Sciences, 15, disease. British Medical Journal, 2, 9-11. 341-347. Smibert, R. M. (1978). The genus Campvlobacter. Annual Kosunen, T. U., Kauranen, O., Martio, J., Prikanen, T., Review of'Microbiology, 32, 673-709. Ponka, A., Hortling, L., Aittoniemi, S., Mutru, O., Penttila, Steele, T. W. and McDermott, S. (1978). Cam pylobacter 0. and Koskimies, S. (1980). Reactive arthritis after enteritis in South Australia. Medical Journal of Australia, Campylobacter jejuni enteritis in patients with HLA-B27. 2, 404-406. Lancet, 1, 1312-1313. Tanner, E. I. and Bullin, C. H. (1977). Campylobacter Lindenstruth, R. W. and Ward, B. Q. (1948). Viability of enteritis. British Medical Journal, 2, 579. Vibrio fetus in hay, soil, and manure. Journal of the Taylor, P. R., Weinstein, W. M. and Bryner, J. H. (1979). American Veterinary Medical Association, 113, 163. Campylobacter fetus infection in human subjects: asso- Lopez Brea, M., Molina, D. and Baquero, M. (1979). ciation with raw milk. American Journal of Medicine. 66, Campylobacter enteritis in Spain. Transactions ofthe Royal 779-783. Society of Tropical Medicine and Hygiene, 73, 474. Tefler Brunton, W. A. and Heggie, D. (1977). Campylobacter- MMWR (1978a). Waterborne Camppylobacter gastro- associated diarrhoea in Edinburgh. British Medical enteritis Vermont. Morbidity and Mortality Weekly Journal, 2, 956. Report, 27, 207. 13 Pathogenic and Nonpathogenic Escherichia coli and Other Bacterial Indicators of Fecal Pollution THIS CHIAPTER combines two distinct areas of coli diarrhea is of limited clinical value and is, in any knowledge. The first two sections ("Description of case, difficult because all patients are excreting large Pathogen and Disease" and "Control Measures") numbers of commensal E. coli, and the laboratory cover recent information on the role of certain types of methods for identifying the suspected pathogens are Escherichia coli as major causes of acute diarrhea in complex and slow. The magnitude of the problem many countries. Subsequent sections of the chapter results from the fact that E. coli virulence factors are briefly review the enormous compilation ofliterature on plasmid encoded and may be transmitted to many other the fecal indicator bacteria, which have been used for 80 Enterobacteriaceae. years as a measure of the degree of fecal contamination of the environment. Occurrence Description of Pathogen and Disease Gastroenteritis due to E. coli occurs in all parts of the world. Particular types of enterotoxigenic E. coli In the last 30 years, and especially in the last tO years, apparently cause infantile diarrhea in particular it has becomeclearthatvariousf s . ci a countries. It is thought that the acquisition of such itjor hausbe e clediartheat vrios fetonbrmofFcly arev s a. infantile strains is one of the major causes of travelers' major cause of diarrhea. This section briefly reviews F diarrhea. Enterotoxigenic E. coli appears to be a more important cause of diarrhea in developing countries than in developed countries. It may be that certain Identification enteroinvasive strains, causing disease in adults, are Diarrhea produced by E. coli cannot be also of restricted geographical distribution. differentiated clinically from similar disease produced by other enteric pathogens. The spectrum of disease Injectious agents includes a cholera-like syndrome produced by enterotoxigenic organisms, a dysentery-like syndrome E. coli is a Gram-negative, rod-shaped bacterium caused by enteroinvasive organisms, and many milder belonging to the family Enterobacteriaceae (figure forms of diarrhea. Asymptomatic infection is very 13-1). These organisms are usually thought of as common. The severity of disease caused by the lactose-fermenting saprophytes, in contrast with the enterotoxigenic E. coli depends upon the degree of non-lactose fermenting Salmonella spp. and Shigella dehydration, and treatment is primarily by rehy- spp. Lactose-fermenting Salmonella spp. and Shigella dration and electrolyte replacement oral rehydration spp. do occur, however, and non-lactose-fermenting having proved very effective in most patients. Death Escherichia coli may be common from some sources. rates of 5-10 percent may be experienced among E. coli is a normal inhabitant of the intestinal tract of untreated infants and children but are very low among man and many other animal species. Conventional those receiving rehydration therapy. Diagnosis of E. biochemical tests used in the identification of bacteria 199 200 ENVIRONMENTAL BIOLOGY & EPIDEMIOLOGY: BACTERIA j i jh' -ij Figure 13-1. Escherichia coli and Streptococcus faecalis under scanning electronmicioscopy. (a) E. coli. Scale bar =1 micrometer.ReproducedbypermissionofDavidScharf'PileofE. co/icells',published in ,s l American Vol 237 No 1 July 1977 pp 22-23.) (b) S.faecalis. Scale bar = 1 micrometer. (Photo: N. J. Horan. Department of Civil Engineering, University of Leeds, Leeds, UK) do not yield information that enables these sap- particularly associated with toxigenicity are 6, 8, 15, 20, rophytic organisms to be differentiated from the 25. 78, 115, 128, 148. 159. pathogenic strains. Serological tests are more useful. The ability to cause disease depends not only on the Particular serological groups, distinguished by their production of enterotoxin but also upon the ability to somatic antigen (O antigen), are commonly associated colonize the intestine. Various colonization factors, or with gastrointestinal disease. However, a particular adhesins, have been described that enable the bacteria strain cannot be assumed to be a pathogenic to attach to the small intestinal mucosa. These representative of a particular 0 group, unless a adhesins are plasmid controlled and are associated pathogenic mechanism (toxin production or invasive- with hair-like protein structures on the bacterial cell, ness) can be demonstrated or epidemiological evidence known as pili or fimbriae. There is now extensive links the strain to an outbreak. evidence that the presence of one or more of three It is valuable to distinguish between three different piliate bacterial antigens (K88, K99, and 987P) is types of pathogen within the E. coli group, a required for successful colonization by ETEC of the description of which follows. small intestine of piglets and calves. More recent work has identified two pili, CFAI and CFAII, as the adhesins ENTEROTOXIGENIC E. COLI (ETEC). Enterotoxigenic of functional importance in human infection. There is strains of E. coli can be the cause of a cholera-like some degree of host specificity among adhesins: K88 is syndrome in infants, children, and adults. ETEC especially associated with piglet infections, and K99 is produce either a heat-labile enterotoxin (LT), serologi- associated with calves and lambs. cally related to cholera enterotoxin, or a heat- stable enterotoxin (ST), which are structurally ENTEROINVASIVE E. COLI (ETEC). Enteroinvasive E. heterogeneous and may consist of LT complexed to coli produce disease by a mechanism similar to that of endotoxin. Some strains produce both toxins. Action Sligialla spp. These organisms invade the colonic of LT is analogous to that of cholera toxin. Production mucosa and cause bloody diarrhea. The property of enterotoxin is controlled by extrachromosomal seems to be restricted to a few 0 groups, 0 groups transferable DNA (plasmids). The ability to accept these particularly implicated are 28, 112, 115, 124, 136, 143, plasmids may be enhanced by particular 0 group 144, 147, 152, 164. antigens but, although this may be important in nature, in the laboratory enterotoxin plasmids (ENT) can be ENTEROPATHOGENIC E. COLI (EPEC). Organisms transferred to nonpathogenic 0 groups. 0 groups belonging to this group were first recognized as a result ESCHERICHIA COLI AND OTHER BACTERIAL INDICATORS 201 of the serological examination of strains of E. coli cause diarrhea in fourteen volunteers at doses of isolated from outbreaks of diarrheal disease among 106-1010. Two ETEC strains isolated from patients in infants. Though undoubtedly some enterotoxigenic Vietnam caused mild diarrhea (three watery stools in and enteroinvasive strains have been included in this 24 hours) in three out of ten volunteers at a dose of 108, group, the pathogenic mechanism employed by most and severe diarrhea (ten or more watery stools over 48 of these organisms is not known. These strains have hours) in seven out of ten volunteers given a dose of been particularly associated with outbreaks of infantile 10 10. Two EIEC strains at a dose of 108 caused diarrhea gastroenteritis; they may, however, cause disease in (mild or severe) in eight of thirteen volunteers and adults. Experiments in adult volunteers have shown dysentry in three of thirteen volunteers; at a dose of 106 that nontoxigenic and noninvasive strains of E. coli they caused diarrhea in one of fourteen volunteers; and isolated from epidemics are able to produce diarrhea 0 at a dose of 104 they caused no diarrhea in ten groups particularly implicated are 18,20,25, 26, 28,44, volunteers. However, when the 106 dose of EIEC was 55, 86, 111, 112, 114, 119, 125, 126, 127, 128, 142. preceded by 2 grams of sodium bicarbonate, severe diarrhea and dysentery were induced in two of three Reservoirs volunteers. These results suggest a median infective dose (ID50) of around 109 for the ETEC strains tested It seems likely that pathogenic E. coli is and an ID50 of around 108 for the EIEC strains tested. transmitted from man to man. Studies on infection in Those infected excreted 10' EIEC per gram and 10'-109 pigs and calves, when considered in the context of the ETEC per gram of feces. problems that have been experienced in developing animal models of human infection, suggest a considerable degree of host specificity. Nonpathogenic Incubation period or commensal E. coli are numerous in the gut of all Most reports suggest an incubation period of 6 to 72 warm-blooded animals and for this reason have been hours. widely used as indicators of fecal pollution of the environment. Period of communicability Transm.issio The organisms are excreted typically for 3-5 days, but sometimes for 2-3 weeks. Colonization of the In nursery outbreaks, the main route of trans- intestine in which saprophytic F. coli is replaced by mission is by way of the hands of those nursing infected pathogenic E. coli can occur. Asymptomatic carriers of infants. It seems likely that fecal contamination of the ETEC and EPEC have frequently been reported. environment, fomites, and hands constitute the primary means of transmission and infection both among children and adults. Water- and foodborne Resistance outbreaks have been described. The presence of the receptors for K88 antigen in the As with the other bacterial enteric pathogens (except small intestine of the pig is genetically determined. Pigs Shigella), large numbers of ingested organisms are lacking the receptors cannot be infected by ETEC. It required to produce infection in healthy adults. seems likely that among human populations similarly Ferguson and June (1952) fed an EPEC serotype in milk unsusceptible individuals may occur. Over 50 percent to adult male prisoners in the USA. A dose of of children have antibodies to common EPEC serotypes 6.5 x 109 produced moderate or severe diarrhea in by the age of 1 year. These seem to confer resistance to seven of eleven volunteers, whereas a dose of 5.3 x 108 infection. Adults are susceptible to strains they have produced comparable symptoms in only one of twelve not previously encountered. Neonates and infants are subjects. In subsequent experiments, in the same prison the most susceptible group, and breast feeding may (June, Ferguson and Worfel 1953) with a different confer some protection. EPEC serotype, moderate or severe symptoms were produced by 1.6 x 1010 organisms in three of eight volunteers, by 5.3 x 109 in one of eight, by 1.7 x 109 in Epidemiology one of seven, and by 1.4 x 108 in one of eight. The great importance of ETEC in childhood diarrhea DuPont and others (1971) sought to infect adult in developing countries has only recently been male volunteers with EJ1 EC and EIEC strains in milk. An recognized. Knowledge of which strains of E. coli cause ETEC strain associated with diarrhea in piglets failed to diarrhea in which ways, and how these infections may 202 ENVIRONMENTAL BIOLOGY & EPIDEMIOLOGY: BACTERIA be diagnosed and categorized, is increasing rapidly. under 2 years old) in Central Java (Indonesia) in The newness and fluid state of the subject mean that January and February. Among those with diarrhea, 15 understanding of E. coli epidemiology is limited and percent excreted rotavirus, 12 percent excreted EPEC, subject to continual revision. In addition, the 24 percent excreted ETEC, 2 percent excreted laboratory techniques for declaring a particular Salmonella, and 2 percent excreted Shigella. Among organism to be ETEC (LT, ST, or LT + ST), EIEC, or EPEC those without diarrhea, the equivalent percentages are developing and are not entirely standardized were 0, 19, 58, 0, and 0, respectively. among different laboratories. Much of the data Freiji and others (1979) found that ETEC and EPEC produced by various surveys in the last five years are accounted for around 6.6 percent of reported therefore not strictly comparable. childhood diarrhea cases in the dry season Several studies in different parts of the world have (March-April), and around 14 percent in the wet shown that E. coli is a major cause of diarrhea, season (May-June), in Addis Ababa (Ethiopia). The especially among young children in poor communities. equivalent proportions for rotavirus were 1 1 and 34 Sack and others (19 75a) studied 59 Apache children, all percent in the dry and wet seasons, respectively. under 5 years of age, hospitalized with acute watery Koornhof and others (1979) recorded in South diarrhea at Whiteriver (Arizona, USA). These patients Africa that 33 percent of 479 black and white children had sixty-four episodes of diarrhea of which 9 percent with diarrhea, mostly under 2 years of age, were were associated with ETEC, I l percent with EPEC, 20 excreting EPEC serotypes compared with only 15 percent with Shigella, 3 percent with Salmonella, and 6 percent of 498 age-matched healthy control children. percent with ETEC plus another bacterial pathogen. Among those excreting EPEC, children with diarrhea Guerrant and others (1975) studied forty infants and excreted significantly greater numbers than healthy children (age 9 days to 10 years) admitted to the control children. ETEC were associated with only 10 hospital in Florian6polis (Brazil) with diarrhea. A percent of diarrhea cases, and no EIEC were recovered. potential pathogen was isolated from thirty-one cases EPEC appeared to be particularly prominent as a cause (78 percent). ETEC alone were isolated from twenty of diarrhea during the annual summer diarrhea peak. cases (50 percent), ETEC plus EIEC from five cases, ETEC In studies conducted prior to about 1970 it was plus Salmonella from two cases, EIEC alone from two common to fail to identify a known pathogen in the cases. EIEC plus Salmonella from one case, and stools of approximately 70 percent of diarrhea cases Salmonella alone from one case. Only one of twenty (see, for instance, Gordon 1964). The enormous healthy controls was excreting ETEC. progress in diarrheal etiology is illustrated by studies in Sebodo and others (1977) examined stool specimens Bangladesh. One study investigated forty-eight pa- from forty-one hospitalized children with acute tients with diarrhea admitted to Matlab hospital who diarrhea and sixteen healthy control children (all did not have V chlolerae, Salmonella, or Shigella in their Table 13-1. Etiology of diarrhea reported to Matlab Hospital, Bangladesh, during 1977 All patients Patients under 5 years Annual incidence Percentage wvith Percentage with Pathogen per 1,000 stated infectioni stated infection Enterotoxigenic E. coli 8.1 25 25 Rotavirus 7.5 23 40 Vibrio cholerue 3.7 12 5 Other vibrios 3.1 9 5 Shigella 1.5 5 5 Salmonella < I 103 fecal coliforms per 100 milliliters. a. When only a single value is given, it is a geometric mean. b. Total coliforms rather than fecal coliforms. ESCHERICHIA COLI AND OTHER BACTERIAL INDICATORS 209 longer than those for Vibrio cholerae and other water, and the warmer the temperature the higher the salmonellae. death rate. Death rates are also higher in natural Waters with little or no microbial life will sustain waters with an active biological population, than in indicator bacteria for considerably longer than similar sterilized, filtered, or other "dead" waters (Poynter and waters with an active flora and fauna. Geldreich (1976) Stevens 1975). Under certain special conditions, reported that the tgo for fecal coliforms in filtered however, growth of indicator bacteria may occur. The stormwater was 40 hours at 20°C and 230 hours at growth phase is usually of limited duration and is 10'C. Gallagher and Spino (1968) found that the tgo for especially likely where nutrient levels are high, fecal coliforms in filtered streamwater was 168 hours at temperatures are warm, but overall microbial and 200C. zoological activity is low. Thus chlorinated effluents As with all the microbial survival data discussed in sometimes provide suitable growth environments for this book, temperature is a crucial factor. Mancini indicator bacteria (see the section below on effluent (1978) used published data to compute a relationship chlorination). Hendricks (1972) found that E. coli between decay rate and temperature in fresh water. The would grow at 30°C in autoclaved river water collected results showed a tgo of about 120 hours at 0°C, falling downstream of a sewage outfall, but not at 20°C or 5oC to about 15 hours at 30°C. Evison and James (1973) and not in autoclaved water collected upstream of the found that indicator bacteria in sewage effluent were outfall (see also Gorden and Fliermans 1978; reduced by 96.5 percent within 5 miles following Hendricks 1971; McFeters, Stuart and Olson 1978). discharge into the Nairobi River (Kenya; temperature Coliform growth is more likely than fecal coliform 18.5°C), whereas only a 56 percent reduction took growth, which is more likely than fecal streptococcal place over an equivalent distance in the River Tees growth (see, for instance, Allen, Pasley and Pierce (UK; temperature 20C). Davenport, Sparrow and 1952). The growth of indicator bacteria is more likely Gordon (1976) found fecal coliform and fecal than the growth of pathogenic bacteria. This latter fact streptococci reductions of only 84 and 67 percent, seriously reduces the value of the indicator bacteria as respectively, after 170 hours of travel under the ice of indicators of pathogenic microbes in situations where the frozen Tanana River (Alaska, USA), whereas a growth is possible or suspected; also, the human similar travel time in a tropical river might cause a excreted viruses (chapters 9-11) can neter increase in reduction of over six log units assuming that there were numbers in the aquatic environment. no additional inputs of fecal pollution. Many investigators have found that total coliform and fecal coliform decay rates are similar, whereas fecal streptococci often persist for longer (for instance, The microbiological quality of groundwater is Cohen and Shuval 1973; Poynter and Stevens 1975).2 becoming an increasing cause for concern worldwide Str. bovis, and to a lesser extent Str. equinus, however, as greater use is made of limited groundwater resources die-off considerably faster than fecal coliforms and and as the practice of disposing of fecal wastes in on- other species of fecal streptococci (Geldreich 1976; site sanitation systems or by land application becomes Geldreich and Kenner 1969; Guy and Small 1977; more common. The potential for groundwater con- McFeters and others 1974). Therefore, because Str. tamination depends upon a complex of factors includ- bovis and Str. equinus are the dominant streptococcal ing the rainfall, the rate of groundwater abstraction, species in some animal feces but never in human feces, groundwater depth and flow patterns, the method of it is sometimes the case that in stored samples waste disposal, and the type, texture, and depth of containing mainly human fecal pollution the fecal the overlying soil or rock. Marzouk, Goyal and Gerba coliform to fecal streptococci ratio falls over time, (1980) reported on the quality of ninety-nine whereas when nonhuman pollution predominates the groundwater samples in Israel. Measures of fecal ratio may rise (Feachem 1975; see chapter 4). coliforms per 100 milliliters were range 0-2 x 104, As a general rule indicator bacteria die in fresh mean l0O, and median 0. Measures of fecal streptococci per 100 milliliters were range 0-104, mean 300, and median 0. Tjostem and others (1977) found low levels 2. A recent report, however, suggested that Str.faecalis survived of coliform contamination in groundwater pumped for a shorter period in Canadian lake water than E. coli (Dutka and from a limestone aquifer in northeastern Iowa (USA). Kwan 1980). There is probably considerable inter- and intra-species variation in survival ability, and studies on mixed populations of Below the limestone, and separated from it by a shale fecal streptococci and E. coli cannot be compared directly with band, was a sandstone aquifer. Water pumped from the studies on the survival of single laboratory-maintained strains. sandstone in uncased wells was also contaminated, but 210 ENVIRONMENTAL BIOLOGY & EPIDEMIOLOGY: BACTERIA wells that were fully cased and grouted through the through the base of waste stabilization ponds (see, for limestone into the sandstone produced relatively instance, Ciravolo and others 1979). unpolluted water. This illustrates an important general There are few data available on the survival of principle-that unpolluted groundwater can often be indicator bacteria in groundwater. It may be obtained from below polluted shallow aquifers if anticipated that survival will be for longer than in must carefully designed abstraction technologies are em- surface waters because of the absence of sunlight, cool ployed. temperatures, and a low level of microbial and Over the past 60 years, studies have been conducted biological activity. Kudryavtseva (1972) reported that to determine the risks of shallow groundwater coliforms introduced into saturated alluvial sands in pollution from pit latrines and septic tank soakage the USSR during the summer survived for up to 3.5 systems. Stiles and Crohurst (1923) recorded the months. A pathogenic serotype of E. coli similarly movement of E. coli for 20 meters horizontally through inoculated into the groundwater survived for 3 months. fine sand in the direction of groundwater flow. In an In groundwater samples returned to the laboratory early study in Singapore (Yeager 1929) to investigate and stored in darkness, coliforms survived for up to 5.5 the required separation of bored hole latrines from months, and pathogenic E. coli survived for up to 4 shallow unprotected wells, it was found that coliforms months. traveled for more than 23 meters but less than 31 These and other data (Allen 1979) show that meters through very permeable soils. Similar studies whether or not on-site soakage or land application in West Bengal (India) showed that wells located 1.6 cause bacterial pollution of the groundwater depends meters from a bored hole latrine (dug in alluvial sandy on numerous site-specific factors. Where soils are of loam with a percolation rate of about 56 meters per fine or medium texture, unsaturated, and more than 1 day) became heavily contaminated with fecal coli- meter deep, little or no bacterial contamination of the forms, whereas most wells located 3.3 meters distant underlying aquifer may occur. Where wastewater can remained uncontaminated (Dyer, Bhaskaran and drain down through "macropores" (such as root Sekar 1945). Further information on the ability of channels, structural voids, rodent burrows, solution excreta disposal systems, especially septic tank channels or fissures) the groundwater may become drainfields, to pollute groundwater is reviewed below significantly polluted with fecal coliforms and fecal in the sections on septic tanks and land treatment. streptococci. Even in this latter case, however, the Groundwater pollution by fecal coliforms and fecal enteric bacterial concentrations in groundwater are streptococci may also be due to the deliberate recharge likely to be far less than in surface waters in the same of sewage effluents to groundwater. Vaughn and others location and will be readily eliminated by any water (1978) studied three sewage recharge installations on treatment process including chlorination. Even where Long Island (New York, USA). At site 1, the untreated waters are being used for domestic purposes, chlorinated effluent contained up to 2.4 x 106 fecal contaminated groundwater will usually pose a lesser coliforms per 100 milliliters, and the groundwater (9 health risk than available surface water. meters below the recharge basins) contained up to 150 fecal coliforms per 100 milliliters. At site 2, the In drinking water chlorinated effluent contained up to 4.3 x 105 fecal coliforms per 100 milliliters, and the groundwater (24 Treated and chlorinated drinking water should meters below the recharge basins) contained up to 930 contain no fecal indicator bacteria. Most people in fecal coliforms per 100 milliliters. At site 3, the tertiary developing countries, however, drink unchlorinated effluent contained up to 9.3 x 105 fecal coliforms per and untreated water. In cases where this water derives 100 milliliters, and the groundwater (5.5 meters below from protected groundwater, or upland surface water the recharge basins) contained up to 150 fecal sources, it may be of moderately good quality (say coliforms per 100 milliliters at a point 46 meters < 100 fecal coliforms per 100 milliliters). In other cases horizontally downslope from the recharge site. Slade the water used may be highly polluted and, on and Edworthy (1981) isolated up to 1.2 x 105 E. coli occasions, has an indicator bacteria concentration and fecal streptococci per 100 milliliters of ground- similar to that of a weak raw sewage. In table 13-2, water from a chalk aquifer directly below groundwater some information on the pollution of drinking water recharge lagoons receiving raw comminuted sewage. sources in developing countries is summarized. Bacteriological aspects of groundwater recharge in This problem of fecally polluted drinking water is by Israel are summarized by Goldshmid (1974). Ground- no means restricted to the developing countries. water contamination may also result from seepage Sandhu, Warren and Nelson (1979) reported that ESCHERICHIA COLI AND OTHER BACTERIAL INDICATORS 211 around 60 percent of people in three counties in South 100 milliliters, and this level of contamination can only Carolina (USA) were served by wells, springs, and be removed by adding a chlorination unit. Therefore, other private water sources. In one county, private to set a zero fecal coliform standard is equivalent to water sources had a mean E. coli count of 1.4 x 106 per requiring that all water supplies be chlorinated (at 100 milliliters and a mean fecal streptococci count of least). Many developing countries, however, have 2.6 x 106 per 100 milliliters. It was concluded that decided to adopt a flexible policy toward water defective septic tank systems were responsible for most treatment and are installing numerous spring, well, or of the fecal contamination. upland stream supplies that have no treatment The question of bacteriological standards for processes. The advantage of designing a supply drinking water remains a subject of considerable without treatment is that it is somewhat cheaper, and debate. In countries where all, or nearly all, the much easier to operate and maintain, than a similar population drink treated piped water it is reasonable supply with treatment (for instance, slow sand filtration and correct to stipulate that no coliforms or other and chlorination). For many developing countries, indicator bacteria should be detected in tap water. therefore, a zero fecal coliform standard is in- Failure to meet this standard indicates a malfunction appropriate. A preferable approach is to set flexible of the treatment plant (especially of the chlorination quality goals that can be changed as the water supply unit) or an inflow of pollution through a damaged sector progresses. To install an improved supply section of the distribution system, which should be providing water with up to 50 fecal coliforms per 100 immediately investigated and rectified. In developing milliliters, for instance, is a great advance when many countries, however, the great majority of the popu- people in the same country may be drinking water lation drink water that is untreated, either from containing over 103 fecal coliforms per 100 milliliters. improved but untreated supplies (such as handpumps) The effect collecting, carrying, and storing water or from unimproved supplies (such as ponds). This have on bacteriological water quality has attracted water, as indicated in table 13-2, may be grossly increasing concern in recent years. Clearly, there is less polluted, and it is pointless for the government of such purpose in supplying good quality water at a public tap a country to require that all water supplies contain no if it is to become subsequently polluted prior to use. If fecal coliforms. At the best such a ruling will simply be water is collected in clean vessels and stored in such a ignored and thus bring similar regulations into way that polluting material cannot enter, water quality disrepute; at the worst it may force people to abandon is likely to improve-as suggested by the data from improved but lightly contaminated supplies in favor of Malumfashi (Nigeria) presented by Tomkins and the only alternative, which may be unimproved and others (1978) and summarized in table 13-2. It may be heavily polluted supplies. For example, there have been more usual, however, for water quality to deteriorate cases where overzealous health officials have closed between collection and use because the water down contaminated shallow tubewells in a village collection vessels are contaminated and the water is because the wells were found to contain 50 fecal stored in the home in such a way that it can be further coliforms per 100 milliliters and have thus forced the contaminated by children and animals. Studies in villagers to use polluted irrigation canals containing Lesotho (Feachem and others 1978) showed that clean 104 fecal coliforms per 100 milliliters. water collected from a handpump (0-6 fecal coliforms The World Health Organization (WHO) has and 0-1 fecal streptococci per 100 milliliters) could generally advocated standards or guidelines for small become considerably contaminated before use (maxi- untreated water supplies that stipulate less than 10 mum of 1,340 fecal coliforms and 4,280 fecal coliforms and zero fecal coliforms per 100 milliliters streptococci per 100 milliliters). Similarly, Oluwande (WHO 1971). These recommendations have been (1980) reported that public tap water in Western State questioned by those primarily concerned with water (Nigeria) contained 0-3 coliforms and 0 fecal coliforms supplies in developing countries on the grounds that per 100 milliliters, whereas stored water in homes they are too stringent (for instance, see Feachem 1977). contained 0-1,800 coliforms and 0-10 fecal coliforms Even if great attention is paid to selecting the purest per 100 milliliters. The epidemiological significance of available water source and distributing the water water pollution occurring after collection is different through a well-designed and well-maintained system, it from that of pollution of the water source. The first type will not in general be possible to meet a zero fecal of pollution promotes intrafamilial disease trans- coliform standard without incorporating chlorination. mission, whereas the second allows the spread of Well-designed untreated spring supplies, for instance, infection throughout a community using a common will typically contain up to about 25 fecal coliforms per source. 212 ENVIRONMENTAL BIOLOGY & EPIDEMIOLOGY: BACTERIA In concluding this section on indicator bacteria in fecal bacteria, especially coliforms, is considerably drinking water, a note of caution must be sounded more extensive. about the validity of the standard tests for fecal Numerous studies have documented high levels of coliforms, which were developed in Europe and North indicator bacteria (up to 103-105 per 100 milliliters) in America, when they are applied to tropical waters. ocean or estuarine waters near sewage outfalls. Recent Some workers studying water pollution in upland examples from the USA include studies at Miami tropical areas, where surface water temperatures are Beach (Florida; Edmond, Schaiberger and Gerba not greatly higher than in temperature zones, have 1978), Honolulu (Hawaii; Loh, Fujioka and Lau obtained satisfactory results using standard methods 1979), the Texas Gulf Coast (Gerba and others 1977; for enumerating fecal coliforms [for instance, Feachem Goyal, Gerba and Melnick 1977, 1978, 1979), Long (1974) in the highlands of Papua New Guinea and Island, (New York; Vaughn and others 1979), and the White, Bradley and White (1972) in Uganda]. Other New York Bight (Berg and Metcalf 1978). Studies from studies in the tropics [for instance, Banerjea and Sen other countries include those at Tel Aviv (Israel; (1940) and Raghavachari and Iyer (1940) in India; Shuval 1978), Alexandria (Egypt; Hakim 1978), Boizot (1941) in Singapore; Evison and James (1973) Kerala (India; Raveendran, Gore and Unnithan 1978). in Kenya; Katugampola and Assim (1958) in Sri Naples (Italy; Evison and Tosti 1980), Tuscany (Italy; Lanka; and Moussa (1965) in Egypt] have detected a Petrilli and others 1979), Whitely Bay (UK; Evison considerable proportion of coliforms of probable and Tosti, 1980), Liverpool (UK; Karthegisan and nonfecal origin that have the ability to ferment lactose Pugh Thomas 1980), Belgium (Yde and de Maeyer- at 44°C. In this respect they mimic the truly fecal Cleempoel 1980), and New South Wales and Tasmania coliforms and are thus able to give false positive (Australia; Roper and Marsall 1979). In several of reactions on standard fecal coliform tests. Recent water these studies (for instance, those in Texas) fecal testing in the Gambia (Barrell and Rowland 1979b) indicator bacteria were isolated at higher con- and Tanzania (Brokunsult and Ross Institute 1978) centrations (10-1,000 times higher) from bottom has shown a high prevalence (up to 55 percent) of false sediments than from the overlying waters. Roper and positive results presumably caused by nonfecal Marshall (1979) showed that E. coli in saline sediments coliforms that reside in warm tropical waters and have were protected against attack by viruses, bacteria, and the ability to ferment lactose at 44°C. There is an amoebae, and growth of coliforms in marine sediments urgent need for the development of a test for fecal has been demonstrated (Gerba and McLeod 1976). indicator bacteria in tropical waters that will reliably Numerous estimates of coliform death rates have and simply distinguish between organisms of enteric been made. Chamberlin and Mitchell (1978) and origin and others that are free-living and adapted to Mitchell and Chamberlin (1978) reviewed eighty-seven warm, aqueous habitats. [See note on page 66.] of these estimates and concluded that the times of 90 percent reduction (tgo) lay between 0.6 and 8 hours, Ill seawflater with a geometric mean of about 2 hours (correspond- ing h- values are 0.3-4 per hour with a mean of 1.15 per The great majority of coastal towns and cities that hour-see footnote 1, above). These values reveal have a sewerage system discharge their sewage into the considerably faster death of coliforms in seawater than sea following little or no treatment. This is true in fresh water (where t90 values are between 20 and 115 throughout the world. The design of these marine hours, with a median of about 60 hours). Death rates of outfalls has attracted considerable interest over the coliforms in seawater are also considerably faster than past two decades and involves complex decisions about the death rates of viruses in seawater (tgo values in the the degree of treatment and the design of the outfall range of 15-70 hours-see chapter 9). There is now and complex tradeoffs between costs and environ- widespread agreement that, owing to the greater mental hazards. The principal health-related fecal persistence of enteric viruses, fecal coliforms are an hazards are the risks to swimmers and the con- inadequate index of saline water quality, especially in tamination of fish and shellfish. shellfish-growing areas (Berg and Metcalf 1978). Fecal To design outfalls in such a way that fecal bacteria streptococci survive longer in marine environments and viruses do not pollute beaches or seafood requires than fecal coliforms (Baross, Hanus and Morita 1975; a detailed knowledge of the dispersion, sedimentation, Hanes and Fragala 1967; Petrilli and others 1979; and death of fecal microorganisms discharged into Vasconcelos and Swartz 1976), but not sufficiently long coastal waters. The information on viruses is briefly for them to act as an adequate indicator of the reviewed in chapter 9, and the available knowledge of enteroviruses. Pichot and Barbette (1978) found a t90 ESCHERICHIA COLI AND OTHER BACTERIAL INDICATORS 213 of 3.7 hours for fecal coliforms and 5.7 hours for fecal Recent evidence from Egypt and the USA (Cabelli streptococci under the same experimental conditions. 1979; Cabelli and others 1979) revealed a small but The reasons for the rapid death of coliforms in measurable difference in the incidence of gastrointes- seawater have been the subject of many investigations tinal illness between swimmers and nonswimmers at (Mitchell 1968). Faust, Aotaky and Hargadon (1975) polluted beaches. The recorded risks of swimming in found temperature, dissolved oxygen, and salinity to be seawater containing 102-103 fecal coliforms per 100 the major determinants of the rate of death, and milliliters were an additional attack rate of 1-2 cases of Enzinger and Cooper (1976), McCambridge and gastrointestinal illness per 100 people in the 8-10 days McMeekin (1979) and Mitchell and Yankofsky (1969) following thevisit to the beach. It must be kept in mind, drew attention to the important role of protozoan however, that especially in developing countries the predators. Gerasimenko (1977) found that oil pol- infections that may be transmitted to swimmers at lution did not affect coliform death rates. polluted beaches will usually be highly endemic in the An increasingly convincing case has been built for community at large (the community producing the the importance of light-induced cell damage in wastes which are polluting the sea), and swimming may determining coliform death rates in sea water constitute a negligible additional risk. Set against this (Chamberlin and Mitchell 1978; Chojnowski, Mancini is the possibility that swimmers from high socio- and Jeris 1979; Gameson and Gould 1975; Gameson economic strata (who experience a low risk at home and Saxon 1967; Mitchell and Chamberlin 1975,1978). due to adequate water supply, sanitation, and hygiene) Experiments on fecal coliforms in Sydney harbor may be exposed to a substantially increased risk of (Australia) showed a minimum daytime t90 of 1.9 infection when they bathe in seawater polluted by the hours and a night time tgo of 40 hours (Bellair, Parr- wastes of all socioeconomic strata. The same level of Smith and Wallis 1977). Fecal streptococci appear to additional risk may apply to tourists who are usually be substantially less sensitive to light than coliforms either local residents from upper socioeconomic (Chamberlin and Mitchell 1978). groups or foreign visitors. Little information is available on the survival of indicator bacteria in tropical seawater. In extrapolat- ing results from temperate areas, temperature is the variable of most importance. Even relatively small The fecal indicator bacteria are excreted by almost temperature differences can substantially affect the all people, and by almost all warm-blooded animals, death rate. Jamieson, Madri and Claus (1976) reported nearly all of the time. They are therefore ubiquitous that in sterilized saline waters a pathogenic serotype of and numerous in all materials containing fresh human E. coli had a tgo of about 40 hours at 40C and about 8 or animal feces. The fecal indicator bacteria are a part hours at 37°C. Vasconcelos and Swartz (1976) of the vast total intestinal microflora. A healthy reported that E. coli concentrations in seawater individual may commonly excrete 1011-1012 bacterial declined by less than 2 log units at 8.9°C, but by 7 log cells per wet gram of feces, and these cells may units at 14.5°C, after 6 days. Burdyl and Post (1979) constitute about 9 percent of the total fecal wet weight studied E. coli survival in the Great Salt Lake (USA) or 25 percent of the fecal dry weight (Geldreich 1978). and estimated a tgo of about 110 hours at 9°C and The composition of this total bacterial population is about 21 hours at 19°C. Faust, Aotaky and Hargadon set out in table 1-6. It is usual for the anaerobes, (1975) reported t,0 values for E. coli in estuarine water especially Bifidobacterium and Bacteroides, to be a of 39 hours at 0°C and 14 hours at 30°C. Mancini more numerous and more stable component of the (1978) reviewed reported death rates and temperatures fecal flora than the fecal coliforms or fecal streptococci and computed typical tgo values of 60 hours at OC and (see, for instance, Mata, Carrillo and Villatoro 1969; 7 hours at 30°C. Clearly, coliforms discharged into Tomkins and others 1981; Zubrzycki and Spaulding tropical seawater will rapidly decline in numbers, as 1962). will other excreted bacteria, although not necessarily at The numbers and the serotypes or species of fecal the same rate. Excreted virus concentrations will coliforms and fecal streptococci excreted by humans decline considerably more slowly (see chapter 9). vary considerably between individuals according to An active debate continues about the magnitude of age (Gorbach and others 1967), diet (Bettleheim and the health risk associated with swimming in fecally others 1977), state of health, and chemical and polluted seawater and the correct approach to water microbiological properties of the intestine. Wheater, quality standards and legislation (Cabelli 1979; Evison Mara and Oragui (1979) studied twelve adults in and Tosti 1980; Moore, Perin and Maiden 1979). Dundee (Scotland) and found between 8 x 104 and 214 ENVIRONMENTAL BIOLOGY & EPIDEMIOLOGY: BACTERIA 8 x 107 fecal coliforms, and between 3 x 102 and effluents. Concentrations of indicator bacteria in 2 x 107 fecal streptococci, per gram of wet feces. sewage vary through the day, but this variability is However, community averages are less variable and considerably less in the sewage derived from large are in the ranges of 106-109 fecal coliforms per gram communities than in that derived from small and 105-10' fecal streptococci per gram (table 1-6). communities. Communities with a high water use per Fecal coliform concentrations are usually higher than capita produce a sewage with a lower concentration of those for fecal streptococci by a factor of 4 or more, at indicator bacteria than communities with lower water least in the developed countries whence most such data usage. Thus, indicator bacteria concentrations in come. sewage in developing countries are generally higher The numbers and serotypes of fecal coliforms than those reported from industrialized countries. excreted by a single individual vary through time due Raw sewage typically contains between 105 and 108 to the influence of many factors. In particular, the fecal coliforms and fecal streptococci per 100 milliliters. proliferation of a pathogenic bacterium may modify Berg and Metcalf (1978) reported between 3.8 x 104 the commensal flora in the intestine. Dale and Mata and 4.6 x 106 fecal coliforms per 100 milliliters of (1968) found that eight children in Guatemala with sewage in the USA. Geldreich (1978) reported that shigellosis excreted between 104 and 108 coliforms per twenty-one towns in the USA had between 3.4 x 105 gram and that coliform excretion had a roughly inverse and 4.9 x 107 fecal coliforms and that seven towns had relation to Shigella excretion. Streptococci were between 6.4 x 104 and 4.5 x 106 fecal streptococci per excreted by the same children in concentrations of 100 milliliters of sewage. Davis (1979) found that raw 108-109 per gram. sewage in Houston (Texas, USA) contained 3 x 10' to Most nonhuman animals excrete 105 or more fecal 3 x 107 fecal coliforms and 5 x 105 to 2 x 106 fecal coliforms and fecal streptococci per gram of feces. streptococci per 100 milliliters. In the Dundee area However, some animals excrete <105 per gram, as (Scotland), raw sewage contained 5.8 x 106 to reported for horses and rabbits, respectively, by 1.5 x 107 E. coli per 100 milliliters (Wheater and others Geldreich (1978) in the USA and by Wheater, Mara 1980). and Oragui (1979) in Scotland. It has often been Evison and James (1973) reported that raw sewage claimed in the literature from the USA (for instance, in Nairobi (Kenya) contained up to 1.6 x 108 E. coli, Geldreich 1976) that fecal streptococci concentrations and up to 3.5 x 107 fecal streptococci, per 100 generally exceed fecal coliform concentrations in milliliters. In contrast, and presumably because of animal feces and that the reverse is true for human higher levels of water use, raw sewage in Pietermaritz- feces. However, Wheater, Mara and Oragui (1979) burg (South Africa) contained only 1.5 x 104 E. coli showed that this was not the case for sheep, pigs, cats, per 100 milliliters (Grabow and Nupen 1972). In dogs, hens, ducks, pigeons, and seagulls in Scotland Brazil, Mara and Silva (1979) reported a mean of (see also Williams Smith and Crabb 1961). This 5 x 107 fecal coliforms and 7 x 106 fecal streptococci variability in fecal coliform to fecal streptococci ratios per 100 milliliters of raw sewage. is one of the reasons for the current rejection of the Concentrations of indicator bacteria in sewage may ratio as a method for distinguishing between human be affected by the presence of industrial wastes that and nonhuman fecal pollution (see chapter 4). often contain chemicals antagonistic to enteric Jordan (1926) studied the survival of E. coli in stored bacteria. Data on raw sewages from different areas of feces. At room temperature, numbers increased to Birmingham (UK) showed E. coli concentrations of 108-101" per gram after 2-5 days and subsequently 1.7-3.7 x 108 per 100 milliliters where sewage was decreased to undetectable levels in 6-12 weeks. At principally of domestic origin, compared with only 37°C, numbers initially increased markedly but then 9 x 105 per 100 millimeters where sewage flow was 60 declined to zero within 1-3 weeks. At 10°C, a slower percent of industrial origin and contained 20-30 increase in numbers occurred, to a maximum of milligrams per liter of phenols (Pike and Carrington l08 1010 per gram after 20 days, and 104 per gram 1979). could still be detected after 23 weeks. Studies of sewage produced by small rural communities in the hills of Yorkshire (UK) have shown the fecal coliform concentrations to vary between 105 and 108 per 100 milliliters, whereas fecal streptococci Because the fecal indicator bacteria are ubiquitous vary between 104 and 107 per 100 milliliters (Feachem, and numerous in feces, they are also ubiquitous and unpublished data). Sanitation technologies that use numerous in raw sewage and in most treated sewage little water, for instance the pour-flush designs, will ESCHERICHIA COLI AND OTHER BACTERIAL INDICATORS 215 produce a sewage with an exceptionally high survived for longer in summer than in winter. At concentration of indicator bacteria. Daniel and Lloyd warmer temperatures (say > 25°C), however, it is likely (1980) reported a geometric mean from twelve samples that a vigorous growth period would be followed by a of 8.4 x 10i coliforms per 100 milliliters of sewage rapid decline. Overall survival times of indicator flowing into an Oxfam sanitation unit installed in a bacteria in sludge in the tropics will typically be shorter refugee camp near Dacca (Bangladesh). than in temperate climates. Some studies on the survival of coliforms and streptococci in sewage are listed in the appendixes of I soil Feachem and others (1980). Survival is greatly prolonged at cool temperatures, when dissolved Fecal indicator bacteria occur in only very low oxygen is low (Hanes, Sarles and Rohlich 1964), or concentrations (typically less than 2 per gram) in when the overall microflora have been reduced by most uncontaminated soils (Geldreich and others chlorination or some other means. In warm climates, 1962). In contrast, they are found in high con- with sewage temperatures around 25-30°C, a >99 centrations in soil wherever effluent, night soil, sludge, percent reduction in indicator bacteria concentrations or manure are being used for irrigation or fertilization may be expected in about 10-15 days, depending on or where livestock are grazing. The literature on the the level of oxygenation of the sewage. It is generally survival of enteric bacteria in soil is extensive and dates reported that fecal streptococci survive for a little back to the early 1920s (see the appendixes of Feachem longer than fecal coliforms in sewage (see, for instance, and others 1980). This literature has been periodically Berg and Metcalf 1978; Cohen and Shuval 1973). reviewed (see, for instance, Elliott and Ellis 1977; One study recorded a far more rapid rate of death for Gerba, Wallis and Melnick 1975a; Rudolfs, Falk and fecal indicator bacteria in sewage under natural Ragotzkie 1950). conditions (Dor, Schechter and Shuval 1976). The Reported survival times vary widely. The work of undiluted raw sewage of Jerusalem (Israel) entered Van Donsel, Geldreich and Clarke (1967) clearly the Nahal Soreq wadi at a rate of about 21,000 cubic demonstrated the importance of sunlight and tempera- meters per day. After a flow of 45 kilometers (which ture in determining the death rate of fecal bacteria in took about 44 hours), at a temperature of around 20°C soil. Times for 90 percent reduction (tgo) varied from a (March), the fecal coliform and fecal streptococci minimum of about 3 days in summer in exposed sites to concentrations were reduced by 99.9 and 99 percent, maxima of about 14 days for E. coli and 20 days for Str. respectively. The combination of warm temperatures, faecalis in autumn and winter at shaded sites. In spring highly turbulent flow in some sections of the wadi, and and winter Str. faecalis survived for approximately a rich algal community contributing photosynthetic twice as long as E. coli whereas in summer and autumn oxygen produced a warm and well-aerated environ- the two survival times were similar. This may have been ment that caused rapid death of excreted bacteria. because some E. coli growth was occurring in summer and autumn. In sludge In Alberta (Canada) studies were conducted on the weekly application of 45 millimeters of unchlorinated Fecal indicator bacteria are always present in high waste stabilization pond effluent to plots of canary concentrations in fresh sewage works sludge. grass (Bell and Bole 1978). The effluent contained Concentrations of 10i-10i total coliforms, 10i_107 between 2.3 x 104 and 1.7 x 105 fecal coliforms per fecal coliforms, and 104 106 fecal streptococci per 100 milliliters, and most coliforms were retained in the gram are normal. Dudley and others (1980) in- upper 80 millimeters of the loamy sand. Fecal coliform vestigated an anaerobically digested sludge and two dieoff occurred in two phases. Over the first 2 days after primary sludges at San Antonio (Texas, USA) and effluent application a 90 percent reduction occurred. found 5 x 10i-5 x 106 fecal coliforms and Subsequently, the reduction was about 33 percent per 7 x 104-5 x 105 fecal streptococci per gram of day at 15°C and about 25 percent per day at 10°C. In suspended solids. spring and summer, little or no fecal coliform As with coliforms in feces, night soil, and soil, contamination could be detected 2 weeks after the coliforms in sludge may survive for several months in cessation of irrigation. cool, moist conditions. Growth may also occur, and Chandler and Craven (1978a) studied the disposal to this will be more rapid at warmer temperatures. land of piggery waste containing 10'-108 E. coli per Edmonds (1976) reported that fecal coliforms in sludge 100 milliliters in Victoria (Australia). E. coli con- applied to forest soil in Washington State (USA) centrations in the soil declined by 99 to 99.99 percent 216 ENVIRONMENTAL BIOLOGY & EPIDEMIOLOGY: BACTERIA after 3-6 weeks, and rapid downward movement of E. plants compared with their survival on the underlying coli was recorded in late summer when the soil was dry soil (Chandler and Craven 1978a, 1978b, 1980). Under and cracked. In other experiments, Chandler and conditions in which E. coli survived on soil for 8 weeks, Craven (1978b) recorded a 99 percent reduction of E. no E. coli were recovered from grass after 16 days. coli in 1 day in dry soil, whereas in saturated soil the Persistence of E. coli on the grass stems was greatest reduction was less than 90 percent after 3 weeks. near the soil surface. Similarly, Chandler and Craven (1980) recorded tg9 Experiments in Alberta (Canada) on the spray values for E. coli at 20°C of 18 days in soil with 30 irrigation of fodder crops with waste stabilization pond percent moisture and 2.5 days in soil with 10 percent effluent (containing 102_106 fecal coliforms per 100 moisture. milliliters) have demonstrated the importance of Kibbey, Hagedorn and McCoy (1978) found that climatic conditions and the anatomy of the plant in the survival of Str.faecalis in various loams was mostly determining the survival of excreted bacteria (Bell dependent upon temperature and moisture levels. The 1976; Bell and Bole 1976). Fecal coliforms on alfafa time for 95 percent reduction (t95) in saturated soils (Medicago sath,a) declined by over 99 percent in 1 day was 94 days at 4°C, 80 days at 10°C, 53 days at 25°C, when temperatures were warm (12-23°C), relative and 29 days at 37°C. In air-dried soil the tr5 values were humidity was low (20-65 percent) and there were 23 days at 4°C, 18 days at 10°C, 9 days at 25°C, and 5 about 9 hours per day of bright sunshine. When days at 37°C. temperatures were cooler (9-18°C), relative humidities Under certain soil conditions coliform and fecal higher (48-95 percent), and the sky was overcast, a 99 coliform concentrations will increase, and this increase percent reduction required 4 days. In contrast, fecal will be more rapid at warmer temperatures (see, for coliforms on reed canary grass (Phalaris arundinacea), instance, Guy and Small 1977). Survival times and the bromegrass (Bromus inermus) and orchard grass potential for growth are influenced by the availability (Dactylis glomerata) grasses that, unlike alfafa, of nutrients in the soil. Thus, survival is prolonged in possess leaf sheaths-only underwent a 99 percent soil that is regularly receiving effluent or night soil reduction in 5 days even in bright weather conditions. applications. Dazzo, Smith and Hubbell (1973) The authors argued that sunlight is an important recorded tgo values forE. coli of 4 days in soil receiving determinant of bacterial death rates and that plant no manure and 8.5 days in soil receiving 50 millimeters anatomy controls the degree to which effluent droplets of cow manure slurry per week. on plant surfaces are exposed to sunlight. Greenhouse Survival of indicator bacteria in soil is influenced by studies (Brown, Jones and Donnelly 1980) showed that moisture content, temperature, shade, soil organic 25 millimeters of simulated rainfall, falling in 1 hour, content and the overall biological activity present in reduced E. coli on grass by 90-99.9 percent. In the the soil. These conditions are so variable that reported absence of rainfall, the same level of reduction under survival times and tgo values cover a wide range. From the same conditions took 10-25 days. an overview of the literature (see the appendixes of Sadovski and others (1978) studied the survival of a Feachem and others 1980), it appears that fecal mutant E. coli inoculated into waste stabilization pond coliforms generally survive for less than 10 weeks, with effluents that were applied to drip irrigation to a 90 percent reduction taking place within 10 days. cucumber plots on two farms in Israel. At one site (air Under cool, moist conditions a hardy residual fraction temperature 13-30°C, soil temperature at noon of fecal coliforms may survive for many months. Where 22-30°C, sunlight 9.5 hours per day, relative humidity conditions are hot and arid very limited survival can be 27-55 percent), a single irrigation was performed with expected, and it is probable that almost complete inoculated effluent containing 107 mutant E. coli per elimination of fecal indicator bacteria will occur within 100 milliliters. Mutant E. coli were still detectable in the 2 weeks. irrigation water, at a concentration of > 103 per 100 milliliters, 8 days after the flow of inoculated effluent. The soil contamination immediately after irrigation On crops with inoculated effluent was 107 mutant E. coli per 100 Crops irrigated or fertilized with effluent, night soil, grams of dry soil and persisted at a level of > 106 per sludge, or manure may be heavily contaminated by 100 grams for at least 8 days. Cucumbers grown in fecal indicator bacteria, whereas untreated plants and exposed soil were contaminated by 104 mutant E. coli crops are not (Geldreich, Kenner and Kabler 1964). per 100 grams immediately following the inoculated Studies in Victoria (Australia) demonstrated the irrigation, and this contamination fell to 65 per 100 very limited survival times of excreted bacteria on grams after 8 days. When the soil and drip lines were ESCHERICHIA COLI AND OTHER BACTERIAL INDICATORS 217 covered with polyethylene sheets to reduce evap- place within I week. In arid regions with low cloud oration and raise temperature, no mutant E. coli could cover, complete elimination is likely to take place be detected on cucumbers 1 day following the within 1 week. inoculated irrigation. At the second site (air tempera- The reduction of fecal contamination of harvested ture 23-28°C, soil temperature at noon 40-43°C, crops depends not only on the microbial death rates on sunlight 11.8 hours per day, relative humidity 62-70 plant surfaces but also on the technology employed for percent), three irrigations were performed with irrigation or fertilization. The use only of treated inoculated effluent containing 4.4 x 1011 mutant E. effluent, night soil or sludge; the application of the fecal coli per 100 milliliters. After the third inoculated material to the soil (for instance, by drip irrigation) irrigation the soil contained 1.3 x 106 mutant E. coli rather than over the crops (for instance, by spray per 100 grams (dry weight), and this contamination fell irrigation); covering the soil with plastic sheets to to 130 per 100 grams after 9 days and maintained this reduce evaporation; and the cessation of irrigation level for a further 11 days. Unlike at the first site, where about two weeks prior to harvesting will all greatly irrigation with uninoculated effluent had continued reduce crop contamination. throughout the study, in this case the irrigation terminated 5 days after the third inoculated irrigation, Infish and shellfish and consequently the soil moisture content fell from 15 percent to 3 percent. Bacterial contamination on Fish and shellfish that live in water contaminated by cucumbers grown in exposed soil rose to 1.7 x 103 fecal discharges are frequently found to contain fecal mutant E. coli per 100 grams but rapidly declined indicator bacteria. Several studies have shown that following the last inoculated irrigation. When the soil these bacteria are not part of the normal flora of the and drip lines were covered with polyethylene sheets, intestines of freshwater or saltwater fish (Geldreich no mutant E. coli could be detected on the cucumbers. and Clarke 1966; Guelin 1962). Fish intestines may Earlier studies at the first site by the same workers contain fecal coliforms and fecal streptococci only (Sadovski, Fattal and Goldberg 1978) showed that when the fish have been living in fecally contaminated harvested cucumbers and eggplants, irrigated with water, and these bacteria may survive, and perhaps sewage effluent containing 106 fecal coliforms per 100 multiply, for periods of up to 14 days (Glantz and milliliters, were contaminated by, on average, 389 fecal Krantz 1965) in the fish intestines. coliforms per 100 grams when drip-irrigated through- Most investigations have concentrated on the out the growing season on exposed soil, but by only 30 bacterial contamination of shellfish rather than fish. per 100 grams when drip-irrigated on soil covered by This is because the method of filter feeding of bivalve polyethylene sheets. Irrigating with sewage effluent only molluscs concentrates bacteria in the same way as it during the early stage of growth (up to flowering) concentrates viruses (see chapter 9; Metcalf 1978; produced a final contamination level on harvested Wood 1979) and because molluscs are often eaten raw vegetables similar to that found when irrigation was or only lightly cooked. Goyal, Gerba and Melnick with fresh water (around 2.5 fecal coliforms per 100 (1979) investigated oyster beds in Galveston Bay grams). (Texas, USA) and found fecal coliform concentrations Other reports of coliform survival on crops are listed per 100 milliliters of up to 2,400, 46,000, and 46,000, in the appendixes of Feachem and others (1980) and respectively, in water, sediment, and oysters. Similar have been reviewed elsewhere (for instance, Elliott and results were obtained by Slanetz, Bartley and Stanley Ellis 1977; Geldreich and Bordner 1971; Rudolfs, Falk (1968). Munger, Heyward and Dutton (1979) recorded and Ragotzkie 1950). Fecal bacteria in soil may be in that fecal coliform concentrations in clams in the relatively sheltered and supportive microhabitats Seattle area (Washington, USA) were up to 59 times where moisture, shade, and nutrient availability permit higher than in the surrounding water. survival for many weeks. In contrast, bacteria on crop Mitchell and others (1966) studied the uptake and surfaces will in general be exposed to desiccation and elimination of E. coli by the Eastern oyster sunlight, and their survival is very much shorter than in (Crassostrea virginica) in sterilized seawater at 20°C. soil. Rapid death is promoted by high air temperatures, When the seawater was inoculated with 103 E. coli per bright sunlight, low relative humidity, and a plant milliliter, the oysters accumulated over 104 E. coli per anatomy that does not offer many sheltered sites. gram within 4 hours. When the seawater contained Under most conditions, fecal indicator bacteria are about 10 E. coli per milliliter, the oysters accumulated unlikely to survive for more than 4 weeks on crop over 100 per gram within 4 hours. When the surfaces with at least a 99 percent reduction taking contaminated oysters were rinsed in clean water and 218 ENVIRONMENTAL BIOLOGY & EPIDEMIOLOGY: BACTERIA placed in sterilized seawater, the E. coli concentrations produced droplets that contained an average declined by 99 percent in 10 hours, and fell below the concentration of E. coli 30 times greater than that in the level of detection after 50 hours. In similar experiments column. In similar experiments Blanchard and Syzdek Hoff and Becker (1969) reported that Olympia oysters (1970) produced droplets that contained up to 1,000 (Ostrea lurida), in sterilized seawater containing 10 E. times more Serratia marcescens per milliliter than the coli per milliliter, accumulated 110-320 E. coli per water column from which the droplets were produced. gram after 24 hours at 6-il VC. When the oysters were The concentration of bacteria in the droplet depended rinsed and replaced in sterilized seawater, E. coli levels on the size of the droplet, with highest concentrations fell to about 1 per gram after 48 hours. occurring in droplets 60-80 micrometers in diameter. Jegathesan and others (1976) purchased three The aerosolized excreted bacteria most encountered species of commonly eaten shellfish (cockles, Anadura by people in developed countries are those produced granosa, and two species of mussels, Modiolus by the flush toilets in their houses. Darlow and Bale senhaussi and M. metcalfi) from markets in Malaysia (1959) inoculated wash-down toilet bowls with and examined them for bacterial entericpathogens. Of 1011_10i2 Serratia marcescens and investigated the twenty cockles examined, nine contained coliforms production of airborne organisms when the low-level, (mean concentration of 8.9 x 104 per gram), and seven 9-liter cistern was flushed. At the level of the seat, near isolations of pathogenic serotypes of E. coli were made. the bowl, 7 x 104 Serratia per cubic meter of air were Of eighteen mussels examined, six contained coliforms isolated, and 1.2 meters above the seat the con- (mean concentration of 1.2 x 106 per gram), and centration was 7 x 102 per cubic meter. About 10 twelve isolations of pathogenic serotypes of E. coliwere minutes after flushing there remained 70 bacteria per made. The authors noted that these shellfish are cubic meter widely distributed about the toilet room. A normally eaten partially cooked in Malaysia. tenfold reduction in the inoculum to the bowl reduced Although most attention in the developed countries the aerosol concentrations by about one-quarter. A has turned to the risks of contaminated shellfish second flush, 15 minutes later and without rein- transmitting excreted virus (especially hepatitis A oculation of bacteria, still produced 2.8 x 104 bacteria virus, rotavirus, and Norwalk agent), the risks of per cubic meter at seat level. Swabs taken from surfaces bacterial infections due to pathogenic E. coli, shigellae, throughout the room yielded Serratia. Adding sheets of salmonellae, and Vibrio cholerae being spread by toilet paper to the bowl before flushing did not affect shellfish harvested from polluted waters are very real aerosol production by the first flush, but increased (Hughes, Merson and Gangarosa 1977; Janssen 1974). aerosol production by the second flush by retaining a Considerable debate surrounds the use of quality greater number of organisms in the bowl during the standards for shellfish growing waters based on first flush. Even with the lid closed, the first flush permissible concentrations of fecal indicator bacteria produced 3.1 x 104 bacteria per cubic meter of air at (Cabelli 1978; Evison 1979; Metcalf 1978). The USA seat level. Aerosol production was unaffected by sets limits of 70 coliforms per 100 milliliters (median whether the seat was covered by its lid or by a value) and 14 fecal coliforms per 100 milliliters (median cardboard replica of the human buttocks. value) for waters used for shellfish production. It is Bound and Atkinson (1966) compared aerosol widely accepted, however, that these bacteriological production by wash-down and syphonic types of flush measures are poor indicators of the risk of viral toilets, each flushed by a low-level, 9-liter cistern. The contamination, and most countries have yet to legislate bowls were inoculated with a suspension of E. coli, and for shellfish water quality or to decide whether a air samples were taken 0.4 meters from the bowl at seat standardbasedonindicatorbacteriaaloneisadequate. level. Wash-down toilets produced on average 13 E. coli per cubic meter of air, whereas syphonic bowls In the air produced only 0.9 per cubic meter. Closing the lid before flushing did not affect aerosol production. Airborne droplets of water and wastewater may Newson (1972) studied hospital toilets in England. contain excreted bacteria, and these may cause He sampled water from the bowls of toilets in normal respiratory or enteric infection if inhaled in sufficient use and found no E. coli in 62 percent of samples (109 of numbers by a susceptible host. The mechanisms by 176); only 5 percent of samples (9 of 176) contained which aerosolized bacteria may be produced are more than 2.5 x 105 per 100 milliliters. The seats, lids, similar to those that generate viral aerosols (see flush handles, and door handles in the same toilets were chapter 9). Baylor, Peters and Baylor (1977) bubbled swabbed, and 6 percent of specimens (19 of 293) were air through a column of liquid containing E. coli and positive for E. coli. When 10l E. coli were added to a ESCHERICHIA COLI AND OTHER BACTERIAL INDICATORS 219 bowl, an aerosol of up to 186 E. coli per cubic meter of (USA). The sewage contained 2 x 1010 coliforms per air was produced. The same proccdure also produced 100 milliliters. Within 5 meters of the source, the air at 70-80 visible droplet splashes, of which 39-75 the activated sludge plant contained 130-390 coliforms contained E. coli. More droplet splashes were per cubic meter, whereas at the trickling filter plant the produced by high-level cistern flushes and, surpris- air contained 21-79 coliforms per cubic meter. Wind ingly, syphonic bowls generated more splashes than speed and air temperature were significantly correlated wash-down bowls. The first flush reduced the with the concentration of airborne coliforms. concentration of inoculated E. coli in the bowl water Katzenelson, Teltch and Shuval (1977) isolated up to from 10' to 106 per 100 milliliters; the second flush 452 coliforms per cubic meter of air 30 meters took the concentration down to 1 O0 per 100 milliliters; downwind of an aerated lagoon in Israel. and the third flush left no E. coli detectable in bowl Goff and others (1973) isolated up to 965 coliforms water. per cubic meter of air 100 meters downwind from Gerba, Wallis and Melnick (1975b) seeded 1011 E. trickling filter plants in the USA. Coliform aerosol coli into a flush toilet bowl with a 14-liter cistern flush. detection increased at high relative humidities and low Total numbers of E. coli in the bowl water were reduced solar radiation. Cronholm (1980) detected aerosolized to 107 after one flush, 104 after two flushes, and enteric bacteria up to 930 meters downwind from small remained at around 104 for at least seven flushes. This activated sludge plants in Kentucky (USA). Foliage was because E. coli were adsorbed to the porcelain downwind of the plants was contaminated by 1-830 inner bowl surface and were gradually eluted by enteric bacteria per square millimeter of leaf surface. successive flushes. Public toilet bowls in normal use Six mice forced to inhale air at a sewage treatment were sampled and found to contain between 102_108 plant and observed for 2 weeks exhibited no symptoms, coliforms per total bowl volume. One flush ejected and cultures of their respiratory organs were negative 27-104 visible droplets, and up to 6.6 x 104 E. coli, for enteric bacteria. when 1011 organisms were seeded into the bowl. A Fedorak and Westlake (1980) sampled total reduction of 5 log units in the number of E. coli in the airborne bacteria at an activated sludge plant at bowl reduced the number ejected by a flush by under 3 Edmonton (Canada) and found up to 1.8 x 103 per log units. The numbers of E. coli ejected were not cubic meter of air, compared to a background level of appreciably affected by whether the bowl contained 27 per cubic meter. Similar bacterial concentrations similar original numbers in culture, homogenized (up to 2.6 x 103 per cubic meter) were found indoors stool, or fecal pellets. An estimated 800-1000 bacteria near taps used to sample sewage and sludge from the fell out on bathroom surfaces after a flush (1011 treatment plant. Increased airborne bacterial con- seeded E. coli in the bowl), and 75-80 percent of these centrations occurred in the laboratory when sludge fell out in the first 2 hours after the flush. Coliforms was being dispensed for analysis and when the floor were detected on surfaces of all of twenty private and was being mopped. public toilets in normal use. Walls, floors, toilet seats, Randall and Ledbetter (1966) studied the aerosols and bowl rims were the most contaminated surfaces. produced by an activated sludge plant in Texas (USA). Sewage treatment plants, especially those that The opportunistic respiratory pathogens Klebsiella, involve the pumping of air or oxygen into sewage or the Aerobacter, and Proteus constituted II percent of all mechanical aeration of a sewage tank, produce aerosol isolates, 19 percent of isolates of enteric origin, and 56 droplets that contain excreted bacteria as well as percent of Enterobacteriaceae. The Klebsiella- excreted viruses (see chapter 9). Bitton and Smith- Aerobacter group survived for longer in the air than Holmes (1978) sampled air above the aeration tank of a other enteric bacteria and made up an increasingly high package sewage treatment plant, above an activated proportion of isolates further from the activated sludge sludge plant, and on the roof of a building in Florida tanks. The authors suggested that Klebsiella should be (USA). In a cubic meter of air above the package plant used as an indicator of bacterial air pollution from there were 154 coliforms, 22 fecal coliforms, and 2 fecal sewage treatment plants. streptococci; above the activated sludge plant there Crawford and Jones (1978) studied the emissions of were 165 coliforms, 27 fecal coliforms, and 5 fecal airborne bacteria from aerated grit removal tanks at a streptococci; and on the roof there were 16 coliforms, 2 sewage treatment plant in Toronto (Canada). The rate fecal coliforms, and 1 fecal streptococcus. of bacterial emission from the tanks was strongly Fannin and others (1977) investigated airborne inversely correlated to relative humidity but not to air coliform bacteria near an activated sludge and a temperature, pressure, or sewage flow rate. The rate of trickling filter sewage treatment plant in Michigan decay of downwind airborne bacterial concentrations 220 ENVIRONMENTAL BIOLOGY & EPIDEMIOLOGY: BACTERIA was correlated only to wind speed. When the decay irrigation sites utilizing sewage effluents (Katzenelson rates of various indicator bacteria were compared it and Teltch 1976; Katzenelson, Teltch and Shuval was found that fecal coliforms decayed faster than total 1977; Teltch and Katzenelson 1978). Coliform bacteria coliforms, which decayed considerably faster than fecal were found in the air up to 350 meters downwind from streptococci. By the use of a mathematical model, the the irrigation site. The concentration of bacteria in the authors predict a maximum downwind travel distance air was directly related to the concentration in the of 505 meters for fecal coliforms and 757 meters for Str. effluent, and coliforms could only be detected in the air faecalis. when their concentration in effluent exceeded 105 per The source of excreted bacterial aerosols that is 100 milliliters. Coliforms survived for longer in receiving the most scientific attention at present is the aerosols when relative humidity was high, when solar spray irrigation of sewage effluents. Sorber and others radiation was low, and when the effluent contained a (1976) investigated airborne bacteria produced by the higher concentration of organic matter. Up to 10 times spray irrigation of secondary sewage effluent at a golf more aerosolized bacteria were detected at night than course in Arizona (USA). The effluent contained a during the day. Earlier studies in Israel (Katzenelson, mean of 3.7 x 105 coliforms and 170 fecal streptococci Buium and Shuval 1976) had suggested that residents per 100 milliliters, and the average background level of on kibbutzim that practised spray irrigation with coliforms in the air was 2.4 per cubic meter. At 47 sewage effluent experienced a higher incidence of some meters downwind of the sprinklers up to 330 coliforms bacterial excreted infections (shigellosis, salmonellosis, per cubic meter were recovered, and at 152 meters only and typhoid) than members of kibbutzim that 30 coliforms per cubic meter were found. Coliform practiced no form of wastewater irrigation. These levels significantly higher than the background were findings have been doubted and appear to be detected up to 198 meters downwind. The aero- contradicted by subsequent work (Feliciano 1979). solization efficiency (the proportion of effluent that Airborne excreted bacteria can be produced by was divided into droplets sufficiently small to remain many situations other than toilet flushing, sewage airborne) was estimated as 0.32 percent. The decay rate treatment, or spray irrigation. Edmonds and Littke of airborne bacterial concentrations was markedly (1978) sampled airborne coliforms 80 millimeters reduced at night. In subsequent experiments at the above anaerobically digested, dewatered (20-40 same site, effluent contained 2.8 x 105 coliforms, percent solids) sludge applied to land. Coliforms in the 2.3 x 104 fecal coliforms, and 1.3 x 103 fecal streptoc- sludge over a 7-month sampling period were between occi per 100 milliliters (Bausum, Schaub and Kenyon 5 x 10i and 3.5 x 10' per gram, while coliforms in the 1978). The concentrations of aerobic bacteria-bearing air ranged from 0 to 1.5 x 104 per cubic meter. particles per cubic meter of air, downwind of the Maximum coliform emission was associated with no sprinklers, were up to 10,500 at 46 meters, up to 4,700 rainfall and high air temperature, wind speed, and solar at 76 meters, up to 3,200 at 100 meters, up to 500 at 150 radiation. Adams and others (1980) have reported on meters, and up to 13 at 560 meters. (All these bacterial aerosol emissions from cooling towers using concentrations are expressed as values in excess of the disinfected sewage effluents or polluted river water. background levels of 15-198 colony-forming particles The risks to health associated with inhaling per cubic meter.) When the effluent was heavily aerosolized bacteria depend on factors such as the dose chlorinated prior to spraying, colony-forming particles inhaled, the dose required to cause an infection, and the fell to between 0 and 57 per cubic meter at 46 meters aerosol size. Katzenelson, Teltch and Shuval (1977) downwind. The proportion of Enterobacteriaceae in estimated that an individual working 100 meters from the total aerobic bacterial flora was 2 percent in the an effluent sprinkler in Israel would inhale about 36 effluent but 26 percent in the aerosol isolates. coliforms every 10 minutes. Considering the very high Parker and others (1977) investigated a spray ratio of coliforms to pathogens, this rate of inhalation irrigation system that utilized effluent from a potato- appears low. Infective doses for some pathogens may processing plant. The sprayed effluent contained be lower, however, by the respiratory route than by the 1.6 x 106 coliforms per 100 milliliters. At 15 meters alimentary route. Crozier and Woodward (1962) downwind there were up to 1,100 coliform-bearing reported that typhoid fever was established in particles per cubic meter, and at 1-1.5 kilometers chimpanzees by the respiratory route with doses of S. downwind there were up to 30 coliform-bearing typhi a thousandfold less than those needed for particles per cubic meter. infection by oral challenge. A series of experiments were conducted in Israel to The infective dose of inhaled bacteria depends in investigate the production of airborne bacteria at spray part upon the ability of the aerosols to penetrate deep ESCHERICHIIA COLI AND OTHER BACTERIAL INDICATORS 221 into the lungs. Lung penetration is especially operators) have higher infection or disease rates than important in the establishment of respiratory in- others (Feliciano 1979). It may be that, in most fections. Aerosols that penetrate best are those which situations, the inhalation of excreted bacteria is are less than 5 or 6 micrometers in diameter (Druett, insignificant compared with the ingestion of the same Henderson and Peacock 1956; Druett and others pathogens and that the numbers of bacteria inhaled are 1953; Harper and Morton 1953; May and Druett usually well below the required infective doses. 1953). Reported aerosol sizes from sewage sources vary considerably but, in general, smaller aerosols pre- dominate as distance from the source increases because Inactivation by Sewage Treatment larger particles have settled. Although only small Processes aerosols are likely to penetrate to the lower respiratory tract, it is probable that bacteria (and viruses) in larger The fate of bacterial indicators of pollution in aerosols caught in the upper respiratory tract may sewage treatment processes has been the subject of a subsequently be swallowed. number of studies over the past 50 years. The literature Baylor, Peters and Baylor (1977) found a significant is not, however, as extensive as might be expected, negative correlation between droplet size and the partly because it is only very recently that the concentration of E. coli within a droplet. Droplets importance of E. coli as an enteric pathogen has been produced by surf and blown into the beach had a mean recognized and partly because the traditional focus of size of 35 micrometers at the water's edge and 21 attention has been the ability of sewage treatment micrometers 10 meters up the beach (Baylor and others processes to improve the physicochemical quality, 1977). Sorber and others (1976) found that 50 percent rather than the microbiological quality, of sewage. of airbome bacteria at a spray irrigation site were Indeed, interest in the performance of sewage associated with particles in the range of 1-5 treatment plants in removing enteric bacteria has been micrometers. Darlow and Bale (1959) found that a so low that many engineers are unaware of the poor toilet flush produced aerosols with a mean diameter of bacterial quality of secondary effluents from con- 2.3 micrometers, 87 percent of them being less than 4 ventional treatment plants. micrometers. Goff and others (1973) recorded that the The interest in enteric bacteria in sewage treatment majority of aerosols emitted by trickling filter plants processes is now increasing for two reasons. First, more were less than 5 micrometers in diameter. Randall and stringent effluent quality legislation is being in- Ledbetter (1966) found that 40 percent of viable troduced in the developed countries, and this has airborne bacteria in the immediate vicinity of activated promoted research into disinfection and tertiary sludge units were associated with particles of less than 5 treatment as methods for improving the quality of micrometers in diameter, but that this proportion rose unsatisfactory secondary discharges. Second, there is to 70 percent at a downwind distance of 6 meters. growing awareness in developing countries of the Teltch and Katzenelson (1978) found that the median dangers of discharging highly pathogenic secondary aerosol size produced by effluent sprinklers in Israel effluents into streams that downstream communities was greater than 7 micrometers but that 50 percent of may use for domestic purposes. bacteria sampled were associated with aerosols of less than 7 micrometers in diameter. The studies reported above, and the laboratory By primary and secondary sedimenration investigations of Poon (1968), clearly show that, Primary sedimentation tanks, with retention times although bacterial aerosol production may be of 2-6 hours, produce quite variable results in removal increased by low relative humidity, high temperature, of indicator bacteria (see the appendixes to Feachem high solar radiation, and high wind speed, these same and others 1980). Usually a reduction of fecal coliforms conditions also promote rapid death and dispersion of and fecal streptococci is reported in the range 0-60 bacteria in the air. Thus the dissemination of percent. For instance, at two sewage treatment plants aerosolized bacteria from treatment plants and spray in Scotland, primary sedimentaton removed on irrigation sites in hot arid climates should be average 32 and 50 percent of E. coli and 57 and 53 appreciably less than that reported from temperate percent of Pseudomonas aeruginosa (Wheater and climates. In addition there is no convincing epidem- others 1980). Removal is primarily caused by iological evidence that those exceptionally exposed settlement of bacteria, which are adsorbed to, or to sources of bacterial aerosols (for instance, workers in entrapped within, solid particles in the influent sewage. fields receiving sprayed effluent or sewage plant The data on bacterial dieoff in sewage reported above 222 ENVIRONMENTAL BIOLOGY & EPIDEMIOLOGY: BACTERIA suggest that only a very small reduction ( < 10 percent) three-compartment septic tank used in Kiangsu would be expected due to natural death in the short Province, China (see also figure 6-1 in Part One). The period during which the sewage resides in the first two compartments have retention times of 10 days sedimentation tank. Growth of indicator bacteria, each, and the third has a retention time of 30 days. especially of total coliforms, is sometimes recorded in Tests on these tanks showed that, in winter at sedimentation tanks. temperatures of 3-7°C, E. coli reductions of 4 log units were achieved (suggesting a tgo of 300 hours). The data (see the appendixes of Feachem and others By storage 1980) suggest that in a well-designed and well- Storage will be an especially effective method of maintained septic tank with 3 days' retention in a warm reducing enteric bacteria in sewage at warm tropical climate (>25°C), a reduction of fecal indicator and subtropical temperatures (say, > 25°C). Although bacteria of 50-95 percent may be achieved. In poorly little specific information is available, it may be designed and poorly maintained tanks (the most usual anticipated that fecal bacteria in warm sewage would kind), little or no reduction can be expected. It must be have a tgo of 120 hours or less. stressed, however, that the distinction between a 90 percent removal (say, influent = 10' per 100 milliliters; By septic tanks effluent = 105 per 100 milliliters) and a 10 percent removal (say, influent= 106 per 100 milliliters; The removal of fecal indicator bacteria by septic effluent = 9 x 105 per 100 milliliters) is trivial. In tanks has attracted increased interest recently because either case the effluent is heavily contaminated with of concern about the pollution of groundwater by enteric bacteria, and the ultimate fate of these bacteria septic tank effluents. A septic tank is simply a settling depends on the method of disposal of the effluent and chamber, or chambers, usually having retention time of the sludge. 3 days or less. In poorly designed tanks, or those Effluents are normally discharged to soakaway pits requiring desludging, there is very considerable solids or drainfields where bacteria may be retained in the soil carryover into the effluent. Enteric bacteria are and eventually die. Under certain conditions, however, removed both by death in the anaerobic liquor and by fecal bacteria may travel from the drainfield to pollute association with solids that settle to the sludge layer. shallow groundwater aquifers or nearby wells. The short retention times, and poor sedimentation Kudryavtseva (1972) recorded that coliforms in- performance that is often the result of insufficiently oculated into saturated alluvial sands (percolation rate frequent desludging, are the reasons why high 13 meters per day) in the USSR traveled for a concentrations of fecal indicator bacteria are found in horizontal distance of not more than 3 meters in the septic tank effluents. direction of groundwater flow. However, the same Viraraghavan (1978) reported that a septic tank in author cited other data from the USSR indicating a Canada produced an effluent containing geometric horizontal travel of indicator bacteria of 850 meters mean values of 2.3 x 106 coliforms, 1.6 x 105 fecal through pebble deposits and 1 kilometer through coliforms, and 1.1 x 105 fecal streptococci per 100 weathered limestone. milliliters. Brandes (1978a) reported that approx- Several studies have shown that the travel of imately 2.5 million residents of Ontario (Canada) use bacterial indicators through soil from pit latrines or septic tank systems. He studied three septic tanks with septic tank drainfields decreases over time as the soil retention times of 2-10 days and recorded the following becomes increasingly clogged with fecal solids and ranges of concentrations of fecal coliforms per 100 biological slime. Caldwell and Parr (1937) found that, milliliters: 4 x 105-2 x 106 in first compartment after two months of operation, fecal coliforms and supernatant, 1 x 105-1 x 106 in second compartment Clostridium perfringens could be recovered at 8 meters, supernatant, 9 x 105_8 x 106 in first compartment and occasionally at 11 meters, from a bored hole sludge, 6 x 104-6 x 105 in second compartment latrine. After 7 months, however, bacterial travel was sludge, and 5 x 105-4 x 106 in the effluents (see also less than 1.5 meters. McCoy and Ziebell (1976) applied Brandes 1978b). McCoy and Ziebell (1976) sampled septic tank effluent (5.1 x 106 fecal coliforms and effluents from five septic tanks in the USA with 7.3 x 106 fecal streptococci per 100 milliliters) to 0.6 retention times of 2-13 days and found geometric meter deep columns of loamy sand at 25°C. At an mean values of 4.2 x 105 fecal coliforms and 3.8 x 103 application rate of 0.1 cubic meters per square meter fecal streptococci per 100 milliliters. per day, 92 percent of fecal coliforms were removed McGarry and Stainforth (1978) have described a over the first 100 days of application. After this time a ESCHERICHIA COLI AND OTHER BACTERIAL INDICATORS 223 clogging zone developed at the top of the column, and in the saturated soils throughout a 32-day sampling removal of fecal coliforms improved to 99.999 percent. period. Reneau and others (1977) recorded the travel of Fecal streptococci removal rates were around 3 log fecal coliforms for a horizontal distance of at least 28 units during the first period and over 6 log units after meters from a septic tank drainfield through saturated 100 days. In field experiments it was found that an sandy loam in Virginia (USA). At one site, fecal effluent contained 1.9 x 106 fecal coliforms per 100 coliform concentrations were up to 4.6 x 104 per 100 milliliters; the soil in the clogging zone at the base of milliliters adjacent to a drainfield but were never more the drainfield trench contained 4 x 106 per 100 grams; than 430 per 100 milliliters at a distance of 28 meters and the soil 0.3 meters below the clogging zone (see also Reneau and Pettry 1975). Further important contained less than 200 fecal coliforms per 100 grams. work on bacterial movement through saturated soil The authors noted, however, that these are optimal was reported by McCoy and Hagedorn (1979) and removals under ideal conditions in nonaggregated Rahe, Hagedorn and McCoy (1979). soils. Other literature on the retention and survival of Brown and others (1979) studied the movement of bacteria in soil is reviewed above in the sections on septic tank effluent containing 106 fecal coliforms per groundwater and soil and below in the sections on 100 milliliters through a sandy loam, a sandy clay, and filtration and land treatment. A detailed review of the a clay, with percolation rates of 6, 0.9, and 0.06 meters fate of enteric bacteria in septic tank and drainfield per day, respectively. Fecal coliform concentrations systems has been published (Small Scale Waste decreased greatly with increasing distance from the Management Project 1978). septic line, and a 90-99 percent reduction in 50 Septic tank sludge is rich in excreted bacteria millimeters was common. In most tests fecal coliforms (Brandes 1978a, 1978b) and requires treatment by were not present more than 0.3 meters below the septic digestion, drying, or composting prior to application line, and only very occasionally were they detected in to agricultural land. The destruction of fecal indicator leachate drawn from 1.2 meters below the septic line. bacteria in tanks, in drainfields, and in sludges will be The tendency for nearly all fecal coliforms to be more rapid at warmer temperatures; therefore, given concentrated at the interface between the gravel packing correct design and good maintenance, performance in around the septic line and the soil was especially developing countries may often be better than that marked in soils of low permeability and increased with reported from temperate areas. time of effluent application for all soils. Fecal coliform concentrations in the soil decreased by about 99 . . percent in 2 weeks following the termination of effluent By trickling fIters application. Little information is available on the performance of Studies on septic tank drainfields have clearly shown trickling filters as a unit process. Most studies report that the risks of groundwater pollution are very much the removal of fecal indicator bacteria across a greater if the drainfield is located in, or only a little complete trickling filter plant (pretreatment-primary above, the saturated zone. Viraraghavan (1978) sedimentation-trickling filters-secondary sediment- studied the movement of indicator bacteria horizon- ation). tally through sandy clay and clay (percolation rates Literature on fecal indicator bacteria removal in 0.02-1.0 meters per day) from a septic tile discharging trickling filters is listed in the appendixes of Feachem effluent containing about 105 fecal coliforms and fecal and others (1980). In a well-operated plant the trickling streptococci per 100 milliliters. The septic line was 0.6 filter itself may remove 20-80 percent of influent meters below ground level, and the water table was enteric bacteria, whereas the total treatment plant will only 0.15 meters or less below the line. Fifteen meters remove 70-97 percent. Poor maintenance or overload- downslope from the septic line the groundwater ing will result in considerably lower removal rates. contained about 102 fecal coliforms and 102_103 fecal Fecal coliform and fecal streptococci removal rates are streptococci per 100 milliliters. generally similar. Hagedorn, Hansen and Simonson (1978) seeded In Britain it is common for the removal of fecal antibiotic-resistant E. coli and Str. faecalis into two coliforms across complete trickling filter plants to be pits, 0.3 and 0.6 meters deep, dug into saturated silty 90-95 percent. This poor removal performance results loam and clay loam (percolation rates 0.01-0.2 meters in an effluent containing 104-107 fecal coliforms per per day) in Oregon (USA). The bacteria were detected 100 milliliters. Wheater and others (1980) recorded in wells 15 meters from the pits within 8-16 days of that two trickling filter plants in Scotland achieved inoculation, and they survived in appreciable numbers average overall E. coli reductions of 87 and 90 percent 224 ENVIRONMENTAL BIOLOGY & EPIDEMIOLOGY: BACTERIA and produced effluents containing up to 6.9 x 106 and By waste stabilization ponds 1.4 x 106 E. co/i per 100 milliliters. The removal of E. coli and other fecal indicator By activated sludge bacteria in waste stabilization ponds has been studied The removal of fecal indicator bacteria by activated by many investigators throughout the world during the last 30 years (see the appendixes of Feachem and others sldewhat pessesthan isypor,calthoughl. remo i 1980). It is now well established that ponds, if properly somewhat better than by trickling filters. The mean dsge,cnaheesbtnilyhge eoa retention time in the aeration tanks (6-12 hours) is designed, can achieve substantially higher removal such that only a less than 50 percent reduction by rates of fecal bacteria (and indeed of other excreted natural die-off would be expected, even at warm pathogens) than other forms of sewage treatment. For temperatures and assuming that all the liquor were example, Mara and Silva (1979) report the reduction of held for the mean retention time. Most reduction of fecal coliform bacteria in a series of five ponds in indicator bacteria is in practice achievenortheast Brazil, with a total retention time of 29 days indicator bacteria IS in practice achieved by adsorption 1 0 , and an average temperature of 26°C, from 5 x 107 per to flocs, which are subsequently removed in secondary ada vrg eprtr f2',fo e todflcs,awich tar s entlby rem oveding secondar 100 milliliters in raw sewage to 17 per 100 milliliters in sdmtozoatioan tanks,ift and bthegr ofclae the final effluent; this represents a very high overall protozoa (Van der Drift and others 1977). rdcino 9996pret Studies on removal of fecal indicator bacteria by reduction of 99.99996 percent. activated sludge are listed in the appendixes of MECHANISMS OF E. COLI REMOVAL IN PONDS. There Feachem and others (1980). Reductions ofinfluent fecal is a variety of environmental factors that are bacteria are between 0 and 99.9 percent, with some considered to be responsible, or at least partially so, for experimenters reporting increasing numbers during the removal of E. coli and other fecal indicator bacteria aeration. Most experience suggests that reductions will in ponds. These factors include time and temperature, be 80-99 percent across a complete activated sludge ultraviolet radiation, the antibacterial effect of plant that is well-operated and well-maintained but extracellular algal toxins, low concentrations of that does not include effluent disinfection or tertiary dissolved carbon dioxide, high pH, high (especially treatment. Overloaded or poorly maintained plants supersaturated) concentrations of dissolved oxygen, will achieve very much lower removal rates. These low and predation by the microinvertebrate fauna. These levels of removal (always less than 2 log units) factors are reviewed briefly below, but it should be mean that activated sludge plant secondary emphasized that their relative importance, apart from effluents contain high concentrations of enteric perhaps that of time and temperature, is largely bacteria. Berg and Metcalf (1978) reported unknown. 1.1 x 105-4.9 x 106 fecal coliforms per 100 milliliters Compared with other forms of sewage treatment, of activated sludge effluent. The settled sludge from the ponds are characterized by long mean hydraulic secondary sedimentation tanks will also contain a high retention times, ranging from a few weeks in hot concentration of fccal indicator bacteria that have climates to several months in cold climates. Thus, adsorbed to flocs in the aeration tanks. ponds provide a considerably greater opportunity for fecal bacterial removal than other treatment processes. BY oxidation ditch It is now well established (Mara 1976), both Practically no information has been published on theoretically and from field observation, that removal removal of fecal indicator bacteria by oxidation of fecal bacteria is greater in a series of ponds than in a ditches, although a certain amount is known about single pond providing the same overall hydraulic removal of Salmonella (see chapter 15). The process is retention time, and that this efficiency increases with essentially similar t