Effect of ivermectin (Mectizan) on intestinal nematodes.

Ancillary to a community based mass treatment campaign of onchocerciasis with ivermectin, assessment of the drug's effect on various intestinal nematodes was made in Bebeka, Southwest Ethiopia between 23 April and 23 July, 1990. A total of 231 people were invited for the study and all consented. From each, stool specimen was collected before treatment, two weeks and three months after administration of ivermectin at a dose of 150 mcg/kg body weight. Various intestinal parasites were observed in many of the samples, ranging from single parasite up to five mixed infections per slide. Efficacy of ivermectin against Strongyloides stercoralis was 100% throughout the observation period. Eggs of Ascaris lumbricoides were found in 74.5% of the stool samples collected before treatment and this was reduced to 3.5% and 48.9% in the post-treatment samples of 15 days and three months, respectively. Similar observation was made for the other geohelminths at a lower cure rate. This finding shows that apart from its primary purpose in the control of onchocerciasis, ivermectin has the added benefit of eliminating ascaris and strongyloides infection in areas where such parasites are co-endemic. Furthermore, its significant effect on the intensity of the other enteric nematodes will have a great impact on reducing transmission. The public health significance of population based mass chemotherapy with ivermectin is discussed.