Between 1979 and 1980, the incidence, breeding sites and infection rates of Simulium damnosum with Onchocerca volvulus were investigated on rivers Amire-u-Kiriki and Katsina Ala in a local government area of the Benue State of Nigeria, in West Africa. Several breeding sites were located along the rivers. All the Simulium caught were identified as S. damnosum, and a greater number was encountered during the rainy than the dry season. The numbers of infected and infective S. damnosum were ascertained through the dissection of the caught flies; the number of bites per day as well as the number of infective bites per person per day were estimated for each zone of investigation. It was concluded that the areas of investigation are highly endemic for human onchocerciasis, and the consequences of this on the people living in the area are discussed.
