Comparison of two alpha-cyano pyrethroids when impregnated into bednets against a pyrethroid resistant and susceptible strain of Anopheles stephensi (Diptera : Culicidae) and their F-1 progeny

The two alpha-cyano pyrethroid insecticides lambda-cyhalothrin and alpha-cy permethrin were tested as bednet treatments at a target dose of 20 mg m(-2) . To establish their efficacy, female pyrethroid resistant and susceptible Anopheles stephensi Liston, and the F-1-hybrids were allowed to fly freely in a room with a human subject under an impregnated net. Both treatments pr ovided good personal protection by significantly reducing the number of blo od fed mosquitoes compared to an untreated control net. Mortality after 24 h was significantly higher for the alpha-cypermethrin treated net when comp ared to lambda-cyhalothrin. For each insecticide there were no significant differences in the proportion of susceptible homozygotes and F-1-hybrids fo und dead after a 24 h holding period, which suggests that there would be no selection for pyrethroid resistant heterozygotes by either of the insectic ides.