Onchocerciasis in Gilgel Ghibe River Valley Southwest Ethiopia

Objective: To determine the prevalence of onchocerciasis and the entomologi cal transmission indices such as the parous rate and annual transmission po tential (ATP), Setting: Gilgel Ghibe village, Gilgel Ghibe River Valley Southwest Ethiopia between April 1994 and March 1995. Subjects: Two hundred twenty eight subjects of the total 400 population in Gilgel Ghibe village were subjected to parasitological and clinical examina tions. Method: Two skin snips per person were taken and examined for microfilariae of Onchocerca volvulus. Fly collections were done from dawn to dusk from h uman baits seated in pairs at four representative sites at the river bank a nd away from the river bank. Flies were dissected for parity and infections with O. volvulus larvae. Results: Among the 228 people examined, the prevalence of the disease was l ow (17%), being higher in males (19%) than in females (14%), The geometric mean of microfilarial density was 11.1 (range, 1-132) mf per skin snip, Itc hing followed by pigmentary changes were the most common clinical signs and symptoms. The predominant anthropophilic blackfly species was Simulium (Ed wardsellum) damnosum s.l. The annual parous rate and ATP were 74.7% and 166 9.5, respectively, being higher at the river bank than at sites further awa y suggesting a greater risk of infection by the river side, Conclusion: The low prevalence of onchocerciasis in Gilgel Ghibe area vis-a -vis the high ATP level could be due to the possible presence of bovine onc hocerciasis in the area. Further studies employing molecular techniques are thus required to identify O. volvulus from other filariae in flies.