The effects of ivermectin on onchocercal skin disease and severe itching: results of a multicentre trial

OBJECTIVE TO determine the effects of ivermectin in annual, 3-monthly and 6 -monthly doses on onchocercal skin disease (OSD) and severe itching. METHOD A multicentre, double-blind placebo controlled trial was conducted a mong 4072 residents of rural communities in Ghana, Nigeria and Uganda. Base line clinical examination categorized reactive skin lesions as acute papula r onchodermatitis, chronic papular onchodermatitis and lichenified onchoder matitis. Presence and severity of itching was determined by open-ended and probing questions. Clinical examination and interview took place at baselin e and each of 5 subsequent 3-monthly follow-up visits. RESULTS While prevalence and severity of reactive lesions decreased for all 4 arms, those receiving ivermectin maintained a greater decrease in preval ence and severity over time. The difference between ivermectin and placebo groups was significant for prevalence at 9 months and for severity at 3 mon ths. Differences between placebo and ivermectin groups were much more prono unced for itching. From 6 months onward, the prevalence of severe itching w as reduced by 40-50% among those receiving ivermectin compared to the trend in the placebo group. CONCLUSION This is an important effect on disease burden as severe itching is for the affected people the most troubling complication of onchocerciasi s. The difference among regimens was not significant, and the recommended r egimen of annual treatment for the control of ocular onchocerciasis appears also the most appropriate for onchocerciasis control in areas where the sk in manifestations predominate. The final determination of the effect on ski n lesions requires a longer period of study.