Simulium exiguum, the vector of Onchocerca volvulus on the Rio Micay, Colombia.

Simulium exiguum were collected in the San Antonio area on the Rio Micay as they blood-fed on a volunteer naturally infected with Onchocerca volvulus. The daily dissection of specimens revealed that delayed larval development was common and 23% of the larvae were abnormally formed. However, third-stage larvae were recovered by late day 5 (140 hours) following engorgement. It is concluded that S. exiguum is the vector of O. volvulus at this Colombian endemic focus even though its host efficiency is somewhat limited. S. metallicum collected near Cali from a naturally infected San Antonio volunteer was shown to be a relatively poor experimental host for O. volvulus.