Cytochrome P450 Monooxygenase Mediated Pyrethroid Resistance in the Urban Dengue Vector, Aedes aegypti (Diptera: Culicidae) from Northern Part of West Bengal, India

Development of pyrethroid resistance in Aedes aegypti (Diptera: Culicidae) can lead to failure of ongoing vector control strategies and thereby, impede prevention of dengue transmission in urban regions of India. Therefore, its resistance status needs to be properly understood to prevent recurring dengue outbreaks in cities. The present study investigated cytochrome P450 monooxygenase (CYP)-mediated pyrethroid resistance in this vector species from dengue endemic northern part of West Bengal, India.

Larvae and pupae of wild Ae. aegypti populations were collected from urban regions of two districts (Siliguri town from Darjeeling and Raiganj from Uttar Dinajpur). Larval and adult bioassays were performed for two synthetic pyrethroids viz. deltamethrin and bifenthrin. Synergist assay with Piperonyl Butoxide (PBO), a CYP blocker, was conducted to understand the involvement of CYPs. Relative expression of four CYP9 family genes: CYP9J24, CYP9J26, CYP9J28 and CYP9J32 was also studied through Quantitative Reverse Transcription PCR (qRT-PCR) in larvae and adults.

Larvae and adults of wild Ae. aegypti populations were found resistant for both pyrethroids. Pre-exposure to PBO restored susceptibility in both larvae and adults, indicates the involvement of CYPs in the observed resistance. Differential over-expression of the CYP9 family genes in larvae and adults strengthened association of CYPs with pyrethroid resistance of studied populations.

A control strategy targeting CYPs can be effective in management of Ae. aegypti in this region. Moreover, use of synergists like CYP blockers can help in restoration of susceptibility to pyrethroids in wild Ae. aegypti populations of northern part of West Bengal.