Ivermectin treatment of onchocercal skin lesions: observations from a placebo-controlled, double-blind trial in Malawi.

To determine effects of ivermectin on skin lesions of onchocerciasis, a placebo-controlled, double-blind trial was carried out in the Thyolo highlands of Malawi involving 70 persons over a 32-month period. Assessment was made using both a clinical numeric grading system and sequential photographs. Among both ivermectin and placebo recipients, there was a significant reduction in both the severity and extent of papular skin lesions. Persons with edematous or lichenified skin lesions of onchocerciasis who received ivermectin showed significantly more improvement than those receiving placebo. Twelve months after the placebo group received ivermectin, their skin lesions were similar to those of the ivermectin group. Changes were most evident for those persons with more severe skin disease in both the ivermectin and placebo groups. Annual ivermectin treatment for onchocercal skin lesions is probably inadequate, and treatment three or four times a year may be required, although the optimum regimen has not been established.