EFFECT OF REPEATED TREATMENTS WITH IVERMECTIN ON THE INCIDENCE OF ONCHOCERCIASIS IN NORTHERN CAMEROON

Mass treatments with ivermectin have been undertaken each year since 1 987 in an area hyperendemic for onchocerciasis in northern Cameroon. T he impact of these successive treatments on the incidence of infection in humans was evaluated by comparing the prevalence of skin microfila riae (PMF) and the mean microfilarial skin densities (MFD) observed in 1987 and 1992 in 5-7-year-old children who had never taken the drug b ut who were members of the treated communities. In 1992, the PMF and t he MFD in children in this age group who never received ivermectin wer e reduced by 55% and 77%, respectively, in comparison with the values observed in 1987, before the first treatment round. These results refl ect a pronounced reduction in the intensity of the transmission of Onc hocerca volvulus in the treatment zone. The influence of the ivermecti n treatment coverage in the human population, as well as the vectorial capacity and the dispersal of the vector blackflies, on the transmiss ion of onchocerciasis is discussed.