Effect of larval competition on the extrinsic incubation period and vectorial capacity of Aedes albopictus for Dengue virus

Ecological factors that influence vector longevity or the extrinsic incubation period of an infectious agent have the potential to significantly alter the vectorial capacity of a vector population. Within artificial containers, larval competition for limited resources is a ubiquitous factor that shapes adult life history traits including longevity and mosquito-pathogen interactions; however its effect on vectorial capacity is poorly understood.  In this study we tested the hypothesis that intraspecific larval competition decreases the extrinsic incubation period of dengue virus (DENV) in Aedes albopictus and modelled the effect of intraspecific larval competition on vectorial capacity.  Aedes albopictus larvae were reared under high or low density conditions, given a DENV-2 infectious blood meal and were assayed for midgut infection rate, disseminated infection rate, and viral titer 6, 9, or 12 days post exposure. We found limited support for our hypothesis; larval competition significantly increased the proportion of Ae. albopictus with a disseminated infection rate 6 days post exposure, but overall larval competition did not significantly increase the proportion of Ae. albopictus with a disseminated infection. Our vectorial capacity model found that the effect of larval competition on the transmission potential of a mosquito population was primarily determined by vector longevity and suggests that if larval competition decreases adult longevity it is likely to decrease vectorial capacity even if vector competence is significantly enhanced.