Transmission of Onchocerca dukei by Simulium bovis in North-Cameroon.

"Wild" Simulium bovis females were collected after they had taken blood on a bait oxen with skin microfilariae (mf) of Onchocerca dukei and Onchocerca ochengi. Flies ingested O. dukei mf in high numbers (13.1 mf per blood fed fly) but rarely mf of O. ochengi (3 mf in 60 flies). In 32 flies dissected 14 to 17 hours after the blood meal, a total of 130 O. dukei mf but no of O. ochengi had migrated to the thorax. Six to 9 days after the blood meal, a total of 203 third stage larvae (L3) were found in 61 surviving flies. Invasive larvae from the head measured 738.0 x 17.8 microns and resembled those of O. dukei obtained by intrathoracic injection of mf in a previous study, but were shorter and thinner than O. ochengi L3. Thus, S. bovis can be seen as an efficient natural vector of O. dukei. Its role in the transmission of bovine and human onchocerciasis in North Cameroon is discussed.