Genetics of resistance to permethrin in Anopheles stephensi.

Pyrethroid resistance has been viewed as a very serious threat to the future of malaria vector control1. However, recently two contrasting outcomes have been reported where resistance has been reported in Anopheles malaria vectors. In West Africa a high frequency of the kdr gene in Anopheles gambiae has not prevented good results with pyrethroid treated bednets in laboratory simulations2, in experimental huts3,4 and in malaria control trials in villages5. However, in South Africa, pyrethroid resistance in An. funestus due to a metabolic mechanism6,7 had a serious impact on the indoor residual spraying programme using a pyrethroid and a steep rise in malaria cases was only reversed by switching back to spraying DDT8 to which the metabolic mechanism does not confer resistance.