Larval environmental stress and Aedes aegypti competence for Sindbis virus

We used a model system consisting of Sindbis virus (SINV) and the yellow fever mosquito Aedes aegypti to evaluate how stress at the larval stage alters adult mosquito fitness and susceptibility to viral infection. Larvae were either reared under optimal conditions (control) or exposed to one of four types of stressors; suboptimal nutrients, starvation, elevated temperature, and a low dose of the insecticide malathion and adult females were fed SINV infectious blood meals. Differential expression of immune-specific genes (cecropin, defensin, transferrin) was quantified in 3-day old females to identify plausible molecular mechanisms associated with mosquito response to stress. There were stress-specific variations in mosquito performance (survival, development time, female size), but all stressors had a consistent effect of significantly increasing susceptibility to viral infection and dissemination relative to the controls. Transferrin was up-regulated in all but starvation treatments while defensin was up-regulated in starvation and temperature stress treatments. Results suggest that stress during larval development may cause alterations in adult mosquito phenotype and immunity that can increase their susceptibility to pathogens.