Pesticide susceptibility status of Anopheles mosquitoes in four flood-affected districts of South Punjab, Pakistan.

Recent floods drastically increased the burden of disease, in particular the incidence of malaria, in the southern districts of the Punjab province in Pakistan. Control of malaria vector mosquitoes in these districts requires the adoption of an appropriate evidence-based policy on the use of pesticides, and having the latest information on the insecticide resistance status of malaria vector mosquitoes is essential for designing effective disease prevention policy. Using World Health Organization (WHO) test kits, the present study utilized papers impregnated with DDT, malathion, deltamethrin, lambda-cyhalothrin, and permethrin, to determine the insecticide susceptibility/resistance status of malaria vector mosquitoes in four flood-affected districts. The test results showed that both Anopheles stephensi and Anopheles culicifacies remained resistant to DDT and malathion. Tests with three commonly used pyrethroids, permethrin, lambda-cyhalothrin, and deltamethrin, detected resistance in the majority of cases, but in a number of localities mortalities with these three pyrethroids ranged from 80-97% and were therefore placed under verification-required status. This status indicates the presence of susceptible individuals in these populations. These results suggest that if appropriate resistance management strategies are applied in these areas, then the development of high levels of resistance can still be prevented or slowed. This study forms an important evidence base for the strategic planning of vector control in the four flood-affected districts.