Expression of cytochrome P450 monooxygenase genes in pyrethroid-resistant Aedes albopictus

Control of dengue vectors with synthetic pyrethroids is employed worldwide but development of pyrethroid resistance in Aedes mosquitoes is a big challenge for successful prevention of dengue. Pyrethroids are of two types: type I (devoid of α-cyano group) and type II (contain α-cyano group) which differ in their toxic effect. Therefore, this study investigated potential difference in the cytochrome P450 monooxygenase (CYP) mediated resistance status against two types of synthetic pyrethroids in wild Aedes (Ae.) albopictus populations from dengue endemic sub-Himalayan West Bengal. The role of CYPs in resistance development was studied through synergist assay and gene expression studies. Widespread resistance was observed against permethrin (type I) and lambdacyhalothrin (type II) in studied populations. Use of Piperonyl Butoxide (PBO) in synergist assay restored susceptibility to both the insecticides and confirmed involvement of CYP in observed resistance. Differential overexpression of three CYP genes, CYP6P12, CYP6A8 and CYP6N3 was observed in all populations and population specific differential induction of CYP6P12 and CYP6A8 upon permethrin and lambdacyhalothrin exposure was also noted. These findings indicate occurrence of monooxygenase mediated pyrethroid resistance in Ae. albopictus populations from this region. Use of monooxygenase blockers can improve the efficacy of pyrethroids for control of this vector.