Prevalence of onchocerciasis in Ile-Ire District, (Ifelodun), Kwara State, Nigeria

A survey to determine the prevalence of onchocerciasis was carried out in the Ile-Ire District of Kwara State, Nigeria between April 1979 and May 1980. Of the 4436 subjects examined, 63% were positive for microfilariae of Onchocerca volvulus in their skin snips and 51% of these had palpable onchocercal nodules. The infection rate was 40% among those under 10 years of age; the rate was significantly higher (75%) among the older subjects. There was no difference in the prevalence of infection between male and female subjects, but the microfilarial density, the prevalence of blindness and the frequency of occurrence of 'leopard skin', were significantly higher for males than for females. While all Fulanis and Agatu migrant farm labourers examined were infected, the infection rate among their counterparts of Yoruba origin was 78%. Although the communities were conscious of the presence and nuisance of Simulium and have adopted various measures against Simulium bites, the local perception of the association between blackflies, 'leopard skin', blindness and other clinical manifestations of onchocerciasis was poor. A background of the study area, the trends and impacts of river-blindness in Nigeria, are given.