The reproductive lifespan of Onchocerca volvulus in West African savanna.

The epidemiological model ONCHOSIM--a model and computer simulation program for the transmission and control of onchocerciasis--has been used to determine the range of plausible values for the reproductive lifespan of Onchocerca volvulus. Model predictions based on different lifespan quantifications were compared with the results of longitudinal skin-snip surveys undertaken in 4 reference villages during 13 to 14 years of successful vector control in the Onchocerciasis Control Programme in West Africa. Good fits between predicted and observed trends in skin microfilarial loads could be obtained for all villages. It is concluded that the reproductive lifespan of the savanna strain of O. volvulus lies between 9 and 11 years, and that 95% of the parasites reach the end of reproduction before the age of 13 to 14 years.