Onchocerca volvulus can be found mainly in West Africa, and also in Central and South America. Most likely, this species was originally only in Africa, and was introduced to the Americas with African slaves. There are two strains of this species, distinguishable at the DNA level by the O-150 PCR test. One strain is typically found in the savanna regions of West Africa and the Americas, while the other strain is commonly found in rain forest areas.
Biogeographic Regions: ethiopian ; neotropical