Malaria: keeping the mosquitoes at bay

Abstract

Neither the use of DDT nor chemoprophylaxis has significantly reduced malaria morbidity and mortality, especially among children. Low-technology measures of reducing man/vector contact are gaining in popularity. Malaria control trials in various sub-Saharan African countries show the promise of permethrin-treated bed nets. Researchers have compared the effect of permethrin-treated bed net use with that of chemoprophylaxis (maloprim) in 17 villages in a primary health care scheme in a rural area of the Gambia. They also gave some children a placebo. 86% of adults in the study area already used bed nets, but only 28% realized mosquitoes caused malaria. The permethrin-treated bed nets had a protective efficacy for overall mortality and malaria-specific mortality of 63% and 70%, respectively, in children from intervention villages. These bed nets reduced malaria morbidity and mortality, even though not all bed nets were impregnated with the target dose of permethrin and 50% of bed nets were laundered at least once a month. The bed nets were effective when people were under them, but not when the people were outdoors. Chemoprophylaxis did not reduce clinical episodes of malaria, prevalence of enlarged spleen, or the presence of parasites. Village reporters and the verbal autopsy technique may have underestimated the actual malaria mortality, however. Bed net impregnation was very cost effective and was as effective as other public health interventions, e.g., measles vaccination. The results of trials in other sub-Saharan countries will provide information on the success of bed net impregnation in areas with more intense malaria transmission and whose mosquito control measures are different from those in the Gambia.