Malaria causes more than a million deaths a year in Africa alone. Attempts to combat the disease have been frustrated on two fronts: acquisition of resistance to antimalarial agents by the parasite itself and acquisition of resistance to insecticides by its mosquito vector, Anopheles gambiae. In the May 8 Nature, Mylene Weill and colleagues at the Institut des Sciences et de l'Evolution, Montpelier, France, identify a mechanism of resistance to organophosphate insecticides, paving the way for a renewed attack on the most common resistant strains (Nature, 423:136-137, May 8, 2003).

Weill et al. compared the sequence of an organophosphate target (the acetylcholinesterase gene ace-1) in a resistant and susceptible strain of the mosquito Culex pipiens — vector of the West Nile virus. Analysis revealed one of 27 nucleotide differences resulting in a G119S substitution that they localized to a position near the active site of...