HLC Dutra, et al. PLoS Negl Trop Dis 18(9): e0012482. https://doi.org/10.1371/journal.pntd.0012482
Abstract Background: We sought to understand how ambient temperature and larval densities in the immature aquatic phases determine adult life history traits and dengue virus loads post-infection. We predicted that larval crowding and high temperatures would both lead to smaller mosquitoes that might struggle to invest in an immune response and, hence, would exhibit high viral loads. Methods. We first examined larval densities from urban and rural areas via a meta-analysis. We then used these data to inform a laboratory-based 2×2 design examining the interacting effects of temperature (21 vs. 26˚C) and density (0.2 vs. 0.4 larvae/mL) on adult life history and dengue virus loads. Results. We found that urban areas had an ~8-fold increase in larval densities compared to more rural sites. Crowding led to slower development, smaller mosquitoes, less survival, lower fecundity, and higher viral loads. The higher temperature led to faster development, reduced fecundity, and lower viral loads. The virus-reducing effect of higher temperature rearing was, however, overwhelmed by the impact of larval crowding when both factors were present. Conclusions. These data reveal complex interactions between the environmental effects experienced by immature mosquitoes and adult traits. They especially highlight the importance of crowding with respect to adult viral loads. Together, these data suggest that urban environments might enhance dengue virus loads and, therefore, possibly transmission, a concerning result given the increasing rates of urbanization globally.