Resistance to Selected Pyrethroid Insecticides in the Malaria Mosquito, Anopheles stephensi (Diptera: Culicidae), From Punjab, Pakistan

Pyrethroids are commonly used insecticides in malaria control programs; however, insecticide resistance limits the benefits gained by using these insecticides. In the present study, we assessed the resistance status for different pyrethroids of the malaria mosquito vector, Anopheles stephensi Liston (Diptera: Culicidae), in the Punjab province, Pakistan. Bioassays were conducted using diagnostic doses following standard World Health Organization protocols: 0.05% λ-cyhalothrin, 0.75% permethrin, 0.15% cyfluthrin, 0.05% deltamethrin, and 0.1% cypermethrin. Field collected An. stephensi from four localities in Punjab (Khanewal, Multan, Lodhran, and Bahawalpur) were reared in the laboratory, and non-blood-fed females were used in the bioassays. An. stephensi from all the study sites except Khanewal were found to be susceptible to permethrin and deltamethrin. Resistance or potential resistance to cypermethrin, λ-cyhalothrin and cyfluthrin was observed from all the study sites. The median and 95% knockdown times (KDT50 and KDT95) estimates for all the tested insecticides also showed similar responses. In conclusion, the study revealed resistance to selected pyrethroids in An. stephensi from some parts of Punjab, Pakistan, underscoring the need to devise a resistance management strategy for effective control of this important malaria vector.