Susceptibility status of Aedes aegypti (Diptera: Culicidae) against insecticides of public health use in Delhi and NCR region, India

Background & objectives: Aedes (Stegomyia) aegypti is a primary vector responsible for the transmission of various arboviral diseases in India. Without an effective drug or vaccine against these diseases, chemical insecticide-based vector control supplemented with source reduction remains the best option for their effective management. The development of insecticide resistance due to the continuous use of insecticides might affect the control operations.Methods: Adults and larvae of Aedes aegypti were collected from different localities in Delhi. Larvae were exposed to discriminating (0.02mg/l) and application (1mg/l) doses of temephos. WHO tube assay was conducted for F1 adults using impregnated insecticide papers of dichlorodiphenyltrichloroethane (DDT), malathion, deltamethrin, permethrin, cyfluthrin, and lambda-cyhalothrin.Results: Larvae of Ae. aegypti were found resistant (76.0%) to the discriminating dose of temephos, whereas suscep-tible (100.0%) to the application dose of the temephos. Adult Aedes (Fl) mosquitoes were resistant to DDT (23.7%), malathion (90.5%), deltamethrin (76.0%), permethrin (96.2 %) cyfluthrin (85.5%), and lambda-cyhalothrin (94.0%).Interpretation & conclusion: Indoor residual spray is not used in Delhi for vector control. Resistance in Aedes might be due to pesticide usage for agricultural activities in peripheral regions of Delhi. There is a need to investigate more on the insecticide resistance mechanisms for indirect resistance development. Understanding the insecticide susceptibility status of urban vectors is critical for planning effective control strategies.