102429 Viewpoints African Programme for Onchocerciasis Control 1995– 2015: Updated Health Impact Estimates Based on New Disability Weights ´ 2, J. Lennert Veerman1,3, Koffi B. Agblewonu2, Luc E. Coffeng1*, Wilma A. Stolk1, Honorat G. M. Zoure Michele E. Murdoch4, Mounkaila Noma2, Grace Fobi2, Jan Hendrik Richardus1, Donald A. P. Bundy5, Dik Habbema1, Sake J. de Vlas1, Uche V. Amazigo6 1 Department of Public Health, Erasmus MC, University Medical Center Rotterdam, Rotterdam, The Netherlands, 2 African Programme for Onchocerciasis Control, Ouagadougou, Burkina Faso, 3 School of Population Health, The University of Queensland, Herston, Australia, 4 Department of Dermatology, Watford General Hospital, Watford, United Kingdom, 5 Human Development Network, The World Bank, Washington, D.C., United States of America, 6 Independent Consultant, Enugu, Nigeria Viewpoint infection and morbidity, but using updated x. Averted YLD were calculated as disability weights for visual impairment, DYLDx ~DNx :dwx , where DNx is the Since 1995, the African Programme for blindness, and troublesome itch. averted number of person-years of symp- Onchocerciasis Control (APOC) has coor- Identical to previously used methods tom x (i.e., difference in annually prevalent dinated mass treatment with ivermectin in [1], we calculated the health impact of cases between the factual and counterfac- 16 sub-Saharan countries (Angola, Bur- APOC for each year between 1995 and tual scenarios, as previously estimated [1]), undi, Cameroon, Central African Repub- 2015, expressed in DALYs averted. The and dwx is the associated updated disabil- lic, Chad, Congo, Democratic Republic of DALY metric is the sum of years of life lost ity weight, derived from the GBD 2010 Congo, Equatorial Guinea, Ethiopia, Li- (YLL) due to premature mortality (from study [5]. beria, Malawi, Nigeria, North Sudan, blindness) and years lived in disability Compared to previous disability weights South Sudan, Uganda, and the United (YLD), weighted by a disability weight [2], updated weights were considerably Republic of Tanzania) with the aim to representing the loss of quality of life [5]. lower for visual impairment (0.033, previ- control morbidity due to infection with DALYs averted were calculated as the ously 0.282) and blindness (0.195, previ- Onchocerca volvulus, a filarial nematode. difference between two scenarios: a factual ously 0.594), reflecting that the loss in Recently, we predicted trends in preva- scenario in which APOC activities have quality of life because of these manifesta- lence of infection, visual impairment, taken place as documented, and a coun- tions is considerably lower than previously blindness, and troublesome itch due to terfactual scenario in which APOC activ- assumed. On the contrary, the disability onchocerciasis in APOC countries for the ities have not taken place at all, effectively weight for troublesome itch has increased period 1995–2015, based on extensive translating to DALYaverted~ DYLLblindness (0.108, previously 0.068). The disability data on pre-control infection levels, pop- z DYLDblindness zDYLDvisual impairment z weight for visual impairment represents ulation coverage of ivermectin mass treat- DYLDitch . Here, DYLLblindness is the ‘‘moderate visual impairment’’ in the ment, and the association between infec- averted number of YLL related to prema- GBD 2010 study. The updated disability tion and morbidity [1]. We also estimated ture mortality from blindness (as previous- weights do not include a category for itch the associated health impact, expressed in ly estimated [1]), and DYLDx is the alone. Hence the disability weight for disability-adjusted life years (DALYs). averted number of YLD due to symptom troublesome itch was derived from a However, the estimated health impact was based on disability weights from the 2004 update of the Global Burden of Citation: Coffeng LE, Stolk WA, Zoure ´ HGM, Veerman JL, Agblewonu KB, et al. (2014) African Programme for Onchocerciasis Control 1995–2015: Updated Health Impact Estimates Based on New Disability Weights. PLoS Disease (GBD) study [2], which have been Negl Trop Dis 8(6): e2759. doi:10.1371/journal.pntd.0002759 criticized for being based solely on the Editor: Thomas S. Churcher, Imperial College London, United Kingdom opinions of health professionals [3,4]. The recently published GBD 2010 study ad- Published June 5, 2014 dressed this criticism by providing updated Copyright: ß 2014 Coffeng et al. This is an open-access article distributed under the terms of the Creative disability weights based on household Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. surveys in Bangladesh, Indonesia, Peru, Funding: This study was funded by the World Health Organization/African Programme for Onchocerciasis and Tanzania, an open internet survey, Control (APOC/CEV/322/07,www.who.int/apoc). HGMZ, KBA, MN, GF, and UVA are or have been employees of and a telephone survey in the United the African Programme for Onchocerciasis Control (APOC), World Health Organization, and were responsible States [5]. As a result of this population- for collection of data on pre-control infection levels and coverage of mass treatment, and contributed to the interpretation of the results and preparation of the manuscript, but were not involved in the data analysis. based approach, the disability weights for visual impairment, blindness, and trouble- Competing Interests: The International Bank for Reconstruction and Development/World Bank serves as Fiscal Agent to WHO APOC through its fiduciary oversight of the APOC Trust Fund and contributed to this some itch have changed considerably and paper through its work with the APOC secretariat in the maintenance of accurate financial records. The should better reflect our ideas and beliefs findings, interpretations and conclusions expressed in this paper do not necessarily reflect the views of the as a society of what constitutes health. For World Bank. Furthermore, HGMZ, KBA, MN, GF, and UVA are or have been employees of the African Programme for Onchocerciasis Control (APOC), World Health Organization. The authors state that their employment has future reference, we provide an updated not caused any conflict of interest in any of the following: study design, data collection, data analysis, estimate of the health impact of APOC interpretation, decision to publish. This does not alter our adherence to all PLOS policies on sharing data and activities, based on previously predicted materials. trends in averted number of cases with * E-mail: l.coffeng@erasmusmc.nl PLOS Neglected Tropical Diseases | www.plosntds.org 1 June 2014 | Volume 8 | Issue 6 | e2759 Figure 1. Disability-adjusted life years (DALYs) lost due to onchocerciasis from 1995 to 2015. The total height of the bars (colored plus blank) represents the estimated number of DALYs lost in a counterfactual scenario without ivermectin mass treatment (increasing trend due to population growth). The colored part of each bar represents the estimated actual number of DALYs lost (declining trend due to ivermectin mass treatment). The blank part of each bar therefore represents the annual number of DALYs averted by ivermectin mass treatment in the total APOC population. doi:10.1371/journal.pntd.0002759.g001 generic class of disability weights for onchocercal itch during ivermectin mass is exactly the same for previous and ‘‘disfigurement with itch or pain.’’ This treatment do not report on insomnia [7,8]. updated estimates). class consists of three severity levels, Therefore, if anything, we may be under- Overall, we estimated that APOC has characterized as ‘‘causing some worry estimating the impact of ivermectin mass cumulatively averted 8.9 million DALYs and discomfort’’ (disability weight 0.029), treatment on the burden of itch (and the due to onchocerciasis through 2010, and ‘‘a person having trouble concentrating associated DALYs averted). will avert another 10.1 million DALYs and sleeping’’ (disability weight 0.187), Figure 1 illustrates trends in DALYs between 2011 and 2015, adding up to a and ‘‘causing a person to avoid social lost due to troublesome itch, visual total of 19.0 million DALYs averted contact, feel worried, sleep poorly, and impairment, and blindness, and DALYs through 2015. These updated estimates think about suicide’’ (disability weight averted by APOC. Table 1 gives more do not differ much from previous estimates 0.562). Based on original precontrol data detailed information on the number of (8.2 million DALYs averted through 2010, from a previously published, multicountry prevalent cases (according to the factual and another 9.2 million between 2011 and study [6] (excluding data from Ghana and scenario) and DALYs lost and averted per 2025). In relative terms, the burden of Cameroon, which were collected based on year. For onchocercal visual impairment onchocerciasis in APOC areas has de- convenience sampling rather than house- and blindness, the updated estimates of creased from 23.1 DALYs per 1,000 hold surveys), we assumed that onchocer- the averted burden turned out lower than persons in 1995 to 8.6 DALYs per 1,000 cal itch regularly causes insomnia in about the previous estimates. In contrast, for persons in 2010, and is expected to further half of the cases and, therefore, calculated troublesome itch, the updated estimate of decrease to 3.7 DALYs per 1,000 persons YLD due to itch using the mean of the the burden averted turned out higher in 2015. disability weights for the first two severity than the previous estimate. For visual The updated disability weights provided levels (0.108). We assumed that this impairment and troublesome itch, the by the GBD 2010 study are based on disability weight also applies during iver- difference between previous and updated population surveys rather than expert mectin mass treatment, even though the estimates was proportional to the change opinion. Therefore, they are presumably fraction of insomniacs among cases of itch in values of the associated disability less subjective and should better reflect our might decrease with repeated mass treat- weights. For blindness, however, this ideas and beliefs as a society of what ments (due to lower infection loads and difference was not proportional, as the constitutes health than previous disability consequent lower severity of itch). Unfor- burden of blindness also included years of weights [5]. However, it has been argued tunately, previous studies on trends of life lost due to premature mortality (which that the disability weights for visual impair- PLOS Neglected Tropical Diseases | www.plosntds.org 2 June 2014 | Volume 8 | Issue 6 | e2759 Table 1. Population at risk, number of cases, and disability-adjusted life years lost and averted due to onchocerciasis in areas covered by APOC. Population size and number of cases of infection Year and disease in APOC areas (thousands) Disability-adjusted life years lost (thousands) Disability-adjusted life years averted (thousands) Population (At risk of Troublesome Visual Troublesome Visual Troublesome Visual infection) Infecteda itch impairment Blindness itch impairment Blindness Total itch impairment Blindness Total 1995 71,474 32,330 10,202 889 404 1,102 29 523 1,654 0 0 0 0 1996 73,310 33,209 10,499 910 410 1,134 30 530 1,694 0 0 0 0 1997 75,195 34,073 10,780 931 418 1,164 31 558 1,753 0 0 0 0 1998 77,132 34,951 10,925 957 427 1,180 32 573 1,785 9 0 21 30 1999 79,122 35,816 10,692 974 430 1,155 32 530 1,717 65 0 79 144 2000 81,165 36,522 10,749 981 427 1,161 32 489 1,683 90 1 135 226 2001 83,144 36,998 10,653 987 420 1,151 33 457 1,640 131 1 180 312 PLOS Neglected Tropical Diseases | www.plosntds.org 2002 85,172 37,338 10,456 995 410 1,129 33 421 1,583 183 2 231 416 2003 87,249 37,502 10,073 990 402 1,088 33 417 1,538 256 3 251 510 2004 89,377 37,458 9,705 977 391 1,048 32 397 1,477 329 4 288 621 2005 91,558 37,196 9,357 965 379 1,011 32 363 1,405 400 6 338 744 2006 93,928 36,779 8,684 951 369 938 31 373 1,342 509 7 349 864 3 2007 96,360 36,093 8,111 931 358 876 31 349 1,256 608 9 390 1,007 2008 98,857 35,085 7,539 910 345 814 30 327 1,171 708 10 431 1,149 2009 101,419 33,811 6,564 885 330 709 29 285 1,024 852 12 492 1,356 2010 104,050 32,246 5,836 854 310 630 28 234 892 971 14 563 1,549 2011 106,750 30,355 5,157 825 290 557 27 206 790 1,086 16 611 1,713 2012 109,521 28,244 4,417 797 271 477 26 189 692 1,208 18 648 1,875 2013 112,366 25,979 3,724 762 254 402 25 188 615 1,327 21 670 2,018 2014 115,287 23,591 3,074 724 237 332 24 165 521 1,442 23 715 2,179 2015 118,285 21,115 2,478 690 220 268 23 145 435 1,552 25 757 2,334 Subtotal 1995–2010 16,289 498 6,827 23,614 5,110 70 3,748 8,929 Total 1995–2015 18,325 623 7,719 26,667 11,724 174 7,149 19,048 a Infection defined as presence of at least one adult female worm. doi:10.1371/journal.pntd.0002759.t001 June 2014 | Volume 8 | Issue 6 | e2759 ment and blindness underestimate the contributor to the burden of onchocer- precontrol prevalence of disfiguring skin burden of vision loss in rural Africa ciasis, rather than eye disease. More- disease in areas endemic for onchocer- [9,10]. One of the main arguments is that over, the true disease burden of oncho- ciasis [6]. This underlines the impor- the surveys used to establish new disability cercal skin disease (and the burden tance of onchocercal skin disease, espe- weights did not adequately cover rural averted by APOC) is still larger than cially in forest areas where vision loss is Africa (Tanzania only). Furthermore, being we estimate here, as our updated esti- relatively rare [16]. strictly a metric of health loss rather than mates do not include disfiguring skin wellbeing [5], DALYs do not capture the disease, or other sequelae potentially effects of vision loss and skin disease on associated with onchocerciasis, such as Acknowledgments socioeconomic status [11] and productivity epilepsy [14] and head-nodding syn- We thank Drs. M. C. Asuzu, M. Hagan, W. H. [12,13]. Therefore, the impact of APOC drome [15]. The additional burden of Makunde, P. Ngoumou (deceased), K. F. most likely encompasses more than what disfiguring skin disease is probably Ogbuagu, D. Okello, G. Ozoh, and J. H. F. we report here in terms of health impact. considerable, given the relatively high Remme for their contributions to precontrol According to our updated estimates, values of the updated disability weights data on nodule prevalence and prevalence of skin disease is now the most important for disfiguring skin disease and the high itch. References 1. Coffeng LE, Stolk WA, Zoure ´ HGM, Veerman the clinical and epidemiological burden of skin 12. Benton B (1998) Economic impact of oncho- JL, Agblewonu KB, et al. (2013) African Pro- disease in Africa. Ann Trop Med Parasitol 96: cerciasis control through the African Pro- gramme For Onchocerciasis Control 1995–2015: 283–296. gramme for Onchocerciasis Control: an over- model-estimated health impact and cost. PLoS 7. Brieger WR, Awedoba AK, Eneanya CI, Hagan view. 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