CLINICAL AND PARASITOLOGICAL RESPONSES AFTER UP TO 6.5 YEARS OF IVERMECTIN TREATMENT FOR ONCHOCERCIASIS

There are plans to use mass treatment with ivermectin to clear all Afr ica of the worst ocular and cutaneous effects of onchocerciasis. Howev er, there remains uncertainty about the most suitable treatment regime n and the likely effects of ivermectin on onchocercal skin disease. We have followed 948 subjects for over 6 years in a double-blind, random ized, controlled study of ivermectin for onchocerciasis in a hyperende mic focus in Sierra Leone. Using an intention-to-treat analysis we fou nd a microfilarial prevalence of 16% 6 months after up to 4 annual dos es of ivermectin, and 13% prevalence in the group receiving up to Io d oses of ivermectin at 6-monthly intervals. Microfilarial loads were we ll suppressed in both groups, but repopulation data suggest that adult female worms are still alive and fecund, strongly underlining the nee d to continue treatment. A clear effect of ivermectin was demonstrated on itching, with about one-third of cases being alleviated. Significa nt reductions in the prevalence of serious hyperkeratosis, and possibl y dyspigmentation (leopard skin), were noted, but not for any other on chocercal skin lesion. Six-monthly and annual treatment regimens with ivermectin were equally effective in terms of dermatological and paras itological impact.