A multi-centre study of the effect of Mectizan treatment on onchocercal skin disease: Clinical findings

A multi-centre, double-blind, placebo-controlled trial of the effect of Mectizan (ivermectin, MSD) treatment on the skin disease and severe itching associated with onchocerciasis was carried out in the forest zones of Nigeria, Ghana and Uganda. Overall, 4072 subjects, none of whom had received Mectizan previously, were enrolled and allocated into four groups, to receive Mectizan every 3, 6 or 12 months or placebo every 3 months. Subjects with skin lesions were stratified within each treatment group to ensure equal representation. Each subject was given a clinical examination and interviewed on enrolment and then 3-monthly for 15 months. The presence and severity of itching were determined by open-ended questions followed by probing questions. Skin lesions were classified and their severity graded using a standard system. Analysis of the results was restricted to the data from the 1530 subjects who received all their scheduled treatments and attended all the follow-up visits. From 6 months onwards, all subjects who had received Mectizan reported less severe itching, had lower prevalences of reactive skin lesions and had less severe skin lesions than those in the placebo group (P < 0.05 for each). The greatest reductions, in both itching and skin disease, were seen in subjects treated with Mectizan every 6 months. Mectizan treatment is therefore beneficial for the control of troublesome itching and for reducing the prevalence and severity of skin disease causes by Onchocerca . It is recommended that mass distribution of Mectizan to communities in the study areas be carried out at 6-monthly intervals for maximum efficacy.