Multigenerational fitness costs of chronic sublethal deltamethrin exposure in Aedes albopictus (Diptera: Culicidae).

Environmental insecticide residues are a growing concern in the management of disease-vector mosquitoes, such as Aedes albopictus (Diptera: Culicidae). While deltamethrin is extensively utilised in mosquito vector control, localised or intermittent sublethal exposure to this insecticide may influence mosquito population dynamics. To investigate the role of environmental residual deltamethrin in inducing transgenerational fitness costs in Ae. albopictus, this study established three different concentrations of deltamethrin solution based on its half-lethal concentration (0.002275 mg/L) for long-term exposure. And four consecutive generations were reared under these conditions. We monitored macroscopic growth and developmental data, reproductive capacity, and expression levels of yolk protein genes (vitellogenin) in each generation. Results showed that sublethal multigenerational deltamethrin exposure significantly prolonged the developmental period of Ae. albopictus; however, it did not have a significant impact on pupation or eclosion rates. In terms of fecundity, exposure to deltamethrin reduced the relative expression levels of vitellogenin-A1 and vitellogenin-C in Ae. albopictus, which was correlated with reduced reproductive output. Furthermore, there was a reduction observed in both single female oviposition rates and egg hatching success among exposed individuals. These findings highlight sublethal responses that may impact population dynamics and reproductive success in the field, underscoring the importance of considering chronic, low-dose insecticide effects in integrated vector management strategies.