on·cho·cer·ci·a·sis 
(
ŏng
′k
ō-s
ər-k
īə-s
ĭs)
n. Any of several diseases caused by infestation with filarial worms of the genus Onchocerca, especially a disease of humans caused by O. volvulus and characterized by nodular swellings on the skin and eye lesions that can result in blindness. Transmitted by black flies of the genus Simulium, the disease occurs in tropical regions of Africa and Central and South America. Also called river blindness.
[New Latin Onchocerca, genus name (Greek onkos, barb + Greek kerkos, tail) + -IASIS.]