A community trial of ivermectin for onchocerciasis in Sierra Leone: clinical and parasitological responses to four doses given at six-monthly intervals.

Clinical and parasitological responses were studied in villagers receiving all 4 doses of treatment, at 6-monthly intervals, in a placebo-controlled community trial of ivermectin for onchocerciasis in Sierra Leone. Skin microfilarial loads were markedly lowered by ivermectin throughout and there were reductions in the severity, but not the prevalence, of skin lesions. Markers of general health and the prevalences of itching, Onchocerca nodules and visual loss were not significantly reduced during the study period. Despite our inability to demonstrate obvious clinical benefit, treatment with ivermectin was well accepted throughout the study. Simple clinical measures for evaluating the short to medium term impact of the mass distribution of ivermectin on populations with onchocerciasis need further development.