Research Article: African Programme for Onchocerciasis Control 1995–2015: Model-Estimated Health Impact and Cost

Date Published: January 31, 2013

Publisher: Public Library of Science

Author(s): Luc E. Coffeng, Wilma A. Stolk, Honorat G. M. Zouré, J. Lennert Veerman, Koffi B. Agblewonu, Michele E. Murdoch, Mounkaila Noma, Grace Fobi, Jan Hendrik Richardus, Donald A. P. Bundy, Dik Habbema, Sake J. de Vlas, Uche V. Amazigo, María-Gloria Basáñez.

Abstract: BackgroundOnchocerciasis causes a considerable disease burden in Africa, mainly through skin and eye disease. Since 1995, the African Programme for Onchocerciasis Control (APOC) has coordinated annual mass treatment with ivermectin in 16 countries. In this study, we estimate the health impact of APOC and the associated costs from a program perspective up to 2010 and provide expected trends up to 2015.Methods and FindingsWith data on pre-control prevalence of infection and population coverage of mass treatment, we simulated trends in infection, blindness, visual impairment, and severe itch using the micro-simulation model ONCHOSIM, and estimated disability-adjusted life years (DALYs) lost due to onchocerciasis. We assessed financial costs for APOC, beneficiary governments, and non-governmental development organizations, excluding cost of donated drugs. We estimated that between 1995 and 2010, mass treatment with ivermectin averted 8.2 million DALYs due to onchocerciasis in APOC areas, at a nominal cost of about US$257 million. We expect that APOC will avert another 9.2 million DALYs between 2011 and 2015, at a nominal cost of US$221 million.ConclusionsOur simulations suggest that APOC has had a remarkable impact on population health in Africa between 1995 and 2010. This health impact is predicted to double during the subsequent five years of the program, through to 2015. APOC is a highly cost-effective public health program. Given the anticipated elimination of onchocerciasis from some APOC areas, we expect even more health gains and a more favorable cost-effectiveness of mass treatment with ivermectin in the near future.

Partial Text: Onchocerciasis is caused by Onchocerca volvulus, a filarial nematode restricted to human hosts. The adult female worms reside in subcutaneous nodules where they produce millions of microfilariae during their on-average ten-year life span [1]. The microfilariae are found predominantly migrating through the skin and eyes and are transmitted by biting flies of the genus Simulium (the vector), an obligatory part of the parasite’s life cycle. Onchocerciasis is responsible for a considerable burden of disease, mainly because of visual impairment, blindness, disfiguring skin lesions, and severe itching, which are the results of continuous exposure to microfilariae. Most of the global burden of onchocerciasis (>99%) is found in sub-Saharan Africa. In the West African savanna, where onchocerciasis is of a severely blinding form (savanna type), fear of blindness previously led to abandonment of fertile river basins. However, by now, onchocerciasis has been largely eliminated from West Africa by the Onchocerciasis Control Programme (1974–2002), which relied on intense vector control and mass treatment with the drug ivermectin [2].

In 1995, the total population size in the APOC target area was 71.5 million (Figure 1), with 30% of the APOC target population living in hyperendemic communities, 31% in mesoendemic communities, 38% in hypoendemic communities surrounded by mesoendemic or hyperendemic areas, and 1% living in non-endemic communities. About 30% of the APOC population lived in savanna areas and 70% in forest or forest–savanna mosaic areas (Table 1). Before the inception of APOC in 1995, about 32 million people (45%) in APOC areas were infected with onchocerciasis, with 404,000 people (0.6%) blind because of onchocerciasis, another 889,000 (1.2%) suffering from visual impairment, and 10 million people (14%) suffering from troublesome itch. In the same year, a total of 1.6 million DALYs (22.8 DALYs per 1,000 persons) were lost due to onchocerciasis: 694,000 because of troublesome itch, 684,000 from blindness, and 251,000 due to visual impairment.

We estimated the health impact and cost of mass treatment with ivermectin for the 20-year period that APOC is scheduled to run as a morbidity control program (1995–2015). Our simulations suggest that mass treatment with ivermectin has markedly reduced the prevalence of infection with O. volvulus, troublesome itch, visual impairment, and blindness in APOC areas, averting an estimated 8.2 million DALYs due to onchocerciasis by 2010 at a nominal financial cost of about US$257 million (excluding cost of donated drugs). We expect that APOC will avert another 9.2 million DALYs between 2011 and 2015, at a nominal financial cost of US$221 million.