Onchocerciasis: a major social problem in West Africa.

Onchocerciasis is one of the most serious blinding diseases in the world, affecting between 20 and 25 million people, of whom 200-500 thousand are blind. In Africa more than half of the countries on the continent are affected, the basin of the Volta river containing one of the largest endemic areas. In this area the unique Onchocerciasis Control Program (OCP) is being undertaken, involving Benin, Ghana, Ivory Coast, Mali, Niger, Togo and Upper Volta. In this region, surveys have shown that 14.78% of the population have microfilariae in their skin biopsies, while in hyperendemic villages the figure rises to 75.2%. In such a village the prevalence of blindness rises steeply with age, from 0% under age 20, to over 40% in the over 50 age group. Various environmental factors relevant to the prevalence and incidence of systemic and ocular onchocerciasis are discussed, and pharmacologic treatment modalities are described. Prevention activities, centred around vector control by insecticides, have been dramatically effective.