INSECTICIDE-IMPREGNATED BED NETS REDUCE MALARIA TRANSMISSION IN RURALZANZIBAR

There has been concern that impregnated bed nets are an insufficiently powerful method to control malaria in areas with very high perennial transmission, as in the humid lowland parts of tropical Africa. We car ried out a 'cross-over' trial among children under 5 years of age in 2 villages in rural Zanzibar. In 1989, one village was supplied with ne wly permethrin-impregnated bed nets whereas the other served as unprot ected control. In 1992, when those nets had lost their insecticidal ac tivity and were badly torn, the village which had previously been the control was given newly impregnated bed nets. Each time, reinfection w ith Plasmodium falciparum was measured after initially clearing the pa rasites by administering a therapeutic dose of sulfadoxine/pyrimethami ne. The introduction of bed nets led to a 74-78% reduction in the week ly rate of reinfection with malaria parasites, in all age groups. The nets apparently also affected perceived clinical symptoms, haemoglobin levels, and the mosquito sporozoite rate.