Response to insecticides and underlying mechanisms of resistance in the field populations of Aedes aegypti Linnaeus (Diptera: Culicidae) in Puducherry, India

Background & objectives: Mosquito-borne diseases are major threats to human health worldwide. Successful control of vector mosquitoes requires periodic updates on their response to the insecticides that are in use. Different classes of neurotoxic insecticides have been used in vector control programs. Ae. aegypti and Ae. albopictus are the primary vectors of dengue and have developed resistance to organophosphates and synthetic pyrethroids that are used in vector control programs. Monitoring insecticide pressure and studying the underlying mechanisms of resistance in the field populations of Aedes aegypti are important to formulate resistant management strategies for their control programs. Methods: Aedes aegypti were collected from study sites Lawspet and Abishegapakkam and F1 progeny was subject to biochemical assays to determine the enzyme activity. Insecticide susceptibility tests were conducted to determine vector susceptibility/resistance to malathion and deltamethrin. Adult dried mosquitoes were subjected to multiplex PCR to detect point mutation in the VGSC gene. Results: Insecticide susceptibility test results revealed that Aedes aegypti is resistant to malathion and incipient resistance to deltamethrin has emerged. It was observed that beta-esterase and monoxygense activity were significantly higher in Lawspet sample than the laboratory strain, whereas it was comparatively lower in Abishegapakkam sample than laboratory strain. Multiplex PCR assays showed no kdr mutation in all Ae. aegypti strains. Interpretation & conclusion: Monitoring insecticide resistance in Ae. aegypti would help the local health authorities to implement a rationalized approach for insecticide use in vector control.