The Collaborative International Dictionary of English v.0.48:

onchocerciasis \onchocerciasis\ n. (Med.)
   An infection with nematodes of the genus Onchocerca,
   especially Onchocerca volvulus. Untreated, such infections
   can cause serious dermatological problems, and in advanced
   cases may lead to blindness. In certain areas of tropical
   Africa the blindness caused by onchocerciasis is called
   river blindness.
   [PJC]