Sublethal exposure to spinetoram impacts life history traits and dengue virus replication in Aedes aegypti.

Insecticides are anthropogenic environmental stressors and also a common stressor for mosquito vectors. However, the use of insecticides is often guided by short-term efficacy, and the sublethal effect on their target or nontarget species has long been ignored. Here, we analyzed how sublethal exposure of the promising vector-control bioinsecticide spinetoram to Aedes aegypti larvae alter adult performance and susceptibility to dengue virus (DENV) infection. We found that the surviving adult mosquitoes were significantly smaller and exhibited weaker blood-feeding capacity than control females, apart from the extended immature development period. In terms of reproductive potential, although the F0 generation produced a similar number of eggs and offspring during the first gonotrophic cycle, the survival rates of the F1 generations were significantly lower as compared to the control group, suggesting transgenerational sublethal effects on the F1 generation. Notably, surviving adult females had higher DENV-2 viral loads than the control group after spinetoram sublethal exposure. Mechanistically, transcriptomic analysis showed that inhibition of oxidative phosphorylation may function in stimulating DENV production in adult Ae. aegypti. In Aag2 cells, significant accumulation of apoptosis, mitochondrial reactive oxygen species production, and DENV-2 replication by spinetoram exposure consistently support our conclusion. Our study highlights the threat of sublethal spinetoram exposure on outbreaks of mosquito-borne viruses.