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

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. Author summary Onchocerciasis, also known as river blindness, is a neglected tropical disease caused by a parasitic worm transmitted through the bite of an infected blackfly. Onchocerciasis is, or used to be, endemic in many West, Central, and East African countries. Mass drug administration (MDA) with ivermectin and vector control have been used to prevent the spread of infection and effectively control onchocerciasis as a public health problem. In Central and East Africa, this was done under the mandate of the African Programme for Onchocerciasis Control (APOC). In 2012, the World Health Organization targeted onchocerciasis for control and elimination. Here, we assess the impact of MDA with ivermectin on the prevalence of onchocercal morbidity in 1990 (pre-control), 2020, and 2030, and calculate the associated burden of disease in terms of disability-adjusted life years (DALYs), a composite measure of life years lost and years lived with disability. By 2030, we expect that 691 thousand DALYs will be lost in countries formerly covered by APOC. This burden is due to onchocercal skin disease in about 3.8 million people and onchocercal eye disease in about 384 thousand people, with most of this burden being concentrated in only a few countries.

Automated summary

The study assessed the impact of mass drug administration (MDA) with ivemectin on onchocercal morbidity in regions formerly covered by the African Programme for Onchocerciasis Control. Results showed a decline in infection cases and disability-adjusted life years (DALYs) lost over time, indicating the significant effectiveness of MDA in alleviating the burden of onchocerciasis.