A trial of permethrin-treated bed nets in the prevention of malaria in Gambian children.

A trial was undertaken in a rural area of The Gambia to investigate the impact of permethrin-treated bed nets on malaria. Two groups of children, matched for age, sex, and malaria exposure, were followed through the rainy season of 1985 for illness and febrile episodes. One group of 205 children slept under permethrin-treated bed nets (0.5 g/m2); 184 children who slept under placebo-treated nets formed the control group. At the end of the rains the children were examined for splenomegaly and blood samples were taken for determination of packed cell volume (PCV) and parasitaemia. Permethrin treatment of bed nets was well accepted and was without side-effects. Children who slept under treated nets had significantly fewer episodes of clinical malaria than control children. However, at the end of the rains there was no significant difference in the prevalence of splenomegaly or parasitaemia or in the mean PCV between the groups. It is suggested that permethrin treatment of nets may have a greater effect on the duration of probing by mosquitoes for a blood meal than on the number of bites received.