[Long-term effect of a single dose of ivermectin on skin microfilarial density in an endemic onchocerciasis area of North Cameroon].

Abstract

The long-term efficacy of a single dose of ivermectin (150 micrograms/kg) on skin microfilarial densities was evaluated by comparing parasite levels, before and after treatment, in 192 patients living in an area endemic for onchocerciasis in North Cameroon. A mass treatment with ivermectin has been undertaken in 1989 in two villages, where pretreatment community microfilarial loads (CMFL) were 5.5 and 25.1 microfilariae per snip. The parasitological examination carried out 32 months later showed that the microfilarial densities in the adults where only 24 and 51% of the initial values, respectively. In a third village, treated once in 1989 but located in an area where annual mass distributions of ivermectin have been undertaken since 1987, the mean microfilarial density 28 months after treatment was only 12% of the initial value. In 1992, the mean microfilarial load in children had decreased significantly in comparison with those of 1989 only in the village where the level of endemicity was initially the lowest. The rate of increase in the number of skin microfilariae after one dose of ivermectin is related with the pretreatment endemicity level. The impact of large-scale ivermectin treatments on the transmission of onchocerciasis enhances the long-term efficacy of this drug on the skin microfilarial densities.