About 40% of the world's population, most of whom live in the poorest countries, are at risk from malaria. In Africa alone, malaria kills nearly a million children each year.1 Although we have the tools to fight malaria, such as insecticides for indoor residual spraying, environmentalist campaigns and some ill conceived decisions on public health policy have limited their use.

A renewed effort is under way to control malaria in sub-Saharan Africa. While heartening, the lead agencies have neglected to rebuild the technical expertise necessary to run effective vertical malaria control programmes. Still cautious of DDT (dichlorodiphenyltrichloroethane) and indoor residual spraying, such programmes have focused on the distribution of bed nets impregnated with insecticides. In this week's BMJ, Hill and colleagues assess the effect of combining an insect repellent with insecticide treated bed nets on Plasmodium falciparum or P vivax malaria in Bolivia.2 The trial found that people who used treated nets and repellent had an 80% reduction in P vivax episodes compared with those who used treated nets alone (incidence rate ratio 0.2, 95% confidence interval 0.11 to 0.38). The number of cases of P falciparum during the study was small and, after adjustment for age, …