Onchocerciasis causes skin and eye disease, visual impairment and neurological problems. It is mostly found in Africa, but also in Latin America and Yemen. The common name, ‘river blindness,’ gives a good indication where the disease can be found: the vector of the parasite, a small black fly of the Simulium species, breeds in rivers where there is turbulence in the water, such as rapids, or where the flow is disturbed by overhanging vegetation.