Population dynamics of some Pakistan mosquitoes: the impact of residual organophosphate insecticide spray on anopheline relative abundance.

Two rounds of residual organophosphate house spray regionally eradicated susceptible endophilic resting anophelines (Anopheles culicifacies, An. stephensi and An. subpictus) from rural villages in Punjab province, Pakistan. Partially exophilic resting species (An. annularis and An. pulcherrimus) also were eliminated from resting within the village, but persisted in bovid bait collections throughout the spray period. The abundance of the partially exophilic resting species returned to prespray levels shortly after insecticide efficacy declined (five to six weeks post-spray), while repopulation of the villages by the endophilic resting species required from 12 to 26 months. Malathion resistance developed rapidly in An. stephensi and resulted in treatment failures two years after this compound was first used for anopheline control in Pakistan.