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Comparison of Ivermectin and Diethylcarbamazine in the Treatment of Onchocerciasis

We compared ivermectin with diethylcarbamazine for the treatment of onchocerciasis in a double-blind, placebo-controlled trial. Thirty men with moderate to heavy infection and ocular involvement were randomly assigned to receive ivermectin in a single oral dose (200 micrograms per kilogram of body weight), diethylcarbamazine daily for eight days, or placebo. Diethylcarbamazine caused a significantly more severe systemic reaction than ivermectin (P less than 0.001), whereas the reaction to ivermectin did not differ from the reaction to placebo. Diethylcarbamazine markedly increased the number of punctate opacities in the eye (P less than 0.001), as well as the number of dead and living microfilariae in the cornea over the first week of therapy. Ivermectin had no such effect. Both ivermectin and diethylcarbamazine promptly reduced skin microfilaria counts, but only in the ivermectin group did counts remain significantly lower (P less than 0.005) than in the placebo group at the end of six months of observation. Analysis of adult worms isolated from nodules obtained two months after the start of therapy showed no effect of either drug on viability. Ivermectin appears to be a better tolerated, safer, and more effective microfilaricidal agent than diethylcarbamazine for the treatment of onchocerciasis.

OCULAR MANIFESTATIONS OF ONCHOCERCIASIS IN A RAIN FOREST AREA OF WEST AFRICA

The epidemiology and natural history of onchocerciasis and its ocular complications in rain forest areas are poorly understood. The present study was conducted on a rubber plantation in a hyperendemic area in the rain forest of Liberia, West Africa, where 800 persons were examined. The prevalence of infection was 84% overall 29% had intraocular microfilariae, and 2.4% were blind in one or both eyes. Onchocerciasis was the cause of all binocular blindness and one-third of all visual impairment. Over half of the visual impairment caused by onchocerciasis was due to posterior segment diseases. Chorioretinal changes were present in 75% of people, and included intraretinal pigment clumping in 52% and retinal pigment epithelium atrophy in 32%. Atrophy of the retinal pigment epithelium was associated with increasing age and severity of infection. Intraretinal pigment was strongly associated with anterior uveitis. There was a strong correlation between uveitis and the inflammatory chorioretinal sequelae: retinitis, intraretinal pigment, subretinal fibrosis, and optic neuropathy. These findings indicate that considerable visual impairment associated with rain forest onchocerciasis is common and is due largely to chorioretinal disease.

Effect of single-dose ivermectin therapy on human Onchocerca volvulus infection with onchocercal ocular involvement.

Ivermectin has shown promise as a potentially safe and effective microfilaricidal drug for the treatment of onchocerciasis. Several limited studies have shown it to have fewer side effects, especially ocular complications, than the currently available drug, diethylcarbamazine. The detailed ocular findings in 200 moderately to heavily infected Liberians who were enrolled in a safety and dose-finding study are presented. They received either 0, 100, 150, or 200 micrograms/kg of ivermectin and were followed up for 12 months. In clinical studies so far carried out ivermectin in a dose of 100, 150, or 200 micrograms/kg has not been associated with any major adverse reactions nor were there any sight-threatening effects even in the presence of severe ocular disease. Each of these doses significantly reduced the ocular microfilaria load for at least 12 months when compared with either the placebo (p less than 0.05) or pretreatment values (p less than 0.001). However, the 100 and 150 micrograms/kg doses caused fewer minor side effects than the higher dose. These results confirm that ivermectin in a single oral dose may be a safe and effective microfilaricidal drug for the treatment of onchocerciasis and that it appears to be free of major ocular side effects.