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. 2021 Jul 26;15(7):e0009604.
doi: 10.1371/journal.pntd.0009604. eCollection 2021 Jul.

The burden of skin disease and eye disease due to onchocerciasis in countries formerly under the African Programme for Onchocerciasis Control mandate for 1990, 2020, and 2030

Natalie V S Vinkeles Melchers  1 , Wilma A Stolk  1 , Welmoed van Loon  1   2 , Belén Pedrique  3 , Roel Bakker  1 , Michele E Murdoch  4 , Sake J de Vlas  1 , Luc E Coffeng  1
Affiliations
Free PMC article

The burden of skin disease and eye disease due to onchocerciasis in countries formerly under the African Programme for Onchocerciasis Control mandate for 1990, 2020, and 2030

Natalie V S Vinkeles Melchers et al. PLoS Negl Trop Dis. .
Free PMC article

Abstract

Background: Onchocerciasis ("river blindness") can cause severe morbidity, including vision loss and various skin manifestations, and is targeted for elimination using ivermectin mass drug administration (MDA). We calculated the number of people with Onchocerca volvulus infection and onchocercal skin and eye disease as well as disability-adjusted life years (DALYs) lost from 1990 through to 2030 in areas formerly covered by the African Programme for Onchocerciasis Control.

Methods: Per MDA implementation unit, we collated data on the pre-control distribution of microfilariae (mf) prevalence and the history of control. Next, we predicted trends in infection and morbidity over time using the ONCHOSIM simulation model. DALY estimates were calculated using disability weights from the Global Burden of Disease Study.

Results: In 1990, prior to MDA implementation, the total population at risk was 79.8 million with 26.0 million (32.5%) mf-positive individuals, of whom 17.5 million (21.9%) had some form of onchocercal skin or eye disease (2.5 million DALYs lost). By 2030, the total population was predicted to increase to 236.1 million, while the number of mf-positive cases (about 6.8 million, 2.9%), people with skin or eye morbidity (4.2 million, 1.8%), and DALYs lost (0.7 million) were predicted to decline.

Conclusions: MDA has had a remarkable impact on the onchocerciasis burden in countries previously under the APOC mandate. In the few countries where we predict continued transmission between now and 2030, intensified MDA could be combined with local vector control efforts, or the introduction of new drugs for mopping up residual cases of infection and morbidity.

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Conflict of interest statement

The authors have declared that no competing interests exist.

Figures

Fig 1
Fig 1. Total number of disability-adjusted life years (DALYs) lost and averted due to onchocerciasis from 1990 to 2030 in countries formerly covered by the African Programme for Onchocerciasis Control.
DALYs are expressed in thousands (x1000). The total height of the blue part of the bars represents the estimated total number of DALYs lost, with different intensities of blue representing four subcategories of onchocercal morbidity (see legend). The total height of the bars (blue plus grey) represents the DALYs lost in a counterfactual scenario without large-scale MDA. The light grey part of each bar therefore represents the annual number of DALYs averted by MDA.
Fig 2
Fig 2. Total number of disability-adjusted life years (DALYs) lost due to onchocerciasis by country in 2030.
Fig 3
Fig 3. Univariate sensitivity analysis for the predicted number of cases with reversible and irreversible onchocercal skin disease by 2030.
Coloured bars represent the difference between the sensitivity analysis and the results of the main analysis (vertical black line). * In the sensitivity analysis, the prevalence of infection and clinical manifestations in hypoendemic areas was assumed to be 1/3 of that in mesoendemic areas (as applied in a previous modelling exercise [2]), instead of ratios based on a more detailed meta-analysis performed for the main analysis (see also Table E in S1 Text).
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NVSVM, WAS, WvL, BP, and LEC received funding from the United States Agency for International Development (USAID, www.usaid.gov) through the Drugs for Neglected Diseases initiative (DNDi, www.dndi.org) (ref no. AID-OAA-G14-00010). The contents are the responsibility of the authors and do not necessarily reflect the views of USAID or the United States Government. For its overall mission, DNDi receives support from UK aid, UK (www.ukaiddirect.org; MOU 2013-2018 and MOU 2017-2021); Médecins sans Frontières (MSF, www.msf.org; MOU 2014-2018 and MOU 2019-2023); and the Swiss Agency for Development and Cooperation, Switzerland (SDC, www.eda.admin.ch/sdc; contract no. 81017718 and no. 81050394). WAS, SJdV, and LEC gratefully acknowledge funding of the NTD Modelling Consortium by the Bill & Melinda Gates Foundation (www.gatesfoundation.org; grant OPP1184344). LEC further acknowledges funding from the Dutch Research Council (NWO, www.nwo.nl; grant 016.Veni.178.023). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.