Work

Biochemical and molecular characterization of organophosphate resistance in Aedes aegypti in the sub-Himalayan region of West Bengal, India

Year: 2026

Type: article

Abstract: Continuous use of organophosphate for dengue vector management has increased the risk of resistance development in Aedes aegypti , threatening the effectiveness of current control programmes. This study evaluated susceptibility and mechanisms associated with organophosphate resistance in Ae. aegypti populations from five dengue-endemic districts of sub-Himalayan West Bengal, India. Larvae and adults were subjected to insecticide bioassays, synergist assays, biochemical assays, gene expression analysis, partial sequencing of the acetylcholinesterase gene (ace-1), and molecular docking. Bioassays confirmed malathion resistance (mortality<90%) in DAR, JAL and ALI populations, whereas UTT and COO exhibited possible resistance (mortality=90–98%). High temephos resistance (RR 50 >10) was detected in DAR, JAL and ALI, while UTT showed moderate resistance (RR 50 =7.31) and COO remained susceptible (RR 50 =2.52). Pre-exposure to triphenyl phosphate restored susceptibility in most populations, indicating possible carboxylesterase-mediated metabolic resistance. Resistant populations exhibited significantly elevated alpha and beta carboxylesterase activity. Stage-specific overexpression was observed, with CCEae3a (13.68–39.21-fold) overexpressed in resistant larvae, whereas CCEae6a (12.25–33.99-fold) was overexpressed in resistant adults and both positively correlating with resistance phenotypes. Enzyme activity and gene expression were significantly correlated with reduced malathion mortality and increased temephos LC 50 . Most individuals from JAL, COO and UTT did not exhibit altered AChE activity, while altered activity was detected in < 25% of individuals from DAR and ALI. Partial ace-1 sequence analysis identified no organophosphate resistance-associated polymorphisms within analysed region, suggesting limited role of target-site insensitivity. Molecular docking suggested possible interactions of malathion and temephos with carboxylesterase. These findings provide biochemical and molecular markers for resistance surveillance and support integrated vector management.

Source: Ecotoxicology and Environmental Safety

DOI: 10.1016/j.ecoenv.2026.120749