Distribution of the blinding and nonblinding strains of Onchocerca volvulus in Nigeria

Onchocerciasis remains an important public health problem throughout much o f sub-Saharan Africa, Nigeria is the country whose population is most affec ted by onchocerciasis; however, little is known concerning the epidemiology of onchocerciasis in this country. Previous studies demonstrated that onch ocerciasis in West Africa exists in two forms, which differ in their clinic al and epidemiologic characteristics. This is believed to be due to the exi stence of 2 strains of Onchocerca volvulus, the causative agent of onchocer ciasis, The O-150 polymerase chain reaction has been developed to different iate these 2 strains, and this method has been used to map the distribution of the blinding and nonblinding strains of O. volvulus in Nigeria. The str ain distribution is consistent with what is known concerning the ecology an d epidemiology of onchocerciasis in this country. The results also suggest that migration may be affecting the historic distribution of the 2 strains of the parasite in Nigeria.