The effect of larval nutritional quantity on aspects of vector competence and vectorial capacity of the malaria mosquito Anopheles stephensi

Evolutionary theory predicts that disease resistance is physiologically costly, resulting in trade-offs with life history traits such as development and survival. For insect vectors of human disease, such trade-offs are likely to influence vector competence, and hence disease risk. Little work has been done on ecologically-mediated disease resistance and how nutrition and body condition can shape vector-parasite interactions. We used Anopheles stephensi mosquitoes and the rodent malaria, Plasmodium yoelii, to investigate whether quality of larval breeding habitat influenced ultimate vectorial capacity of adult mosquitoes. Larvae were reared under two conditions, one receiving an ad libitum diet and one under starvation stress. Upon emergence, adults were provided an infectious blood feed. Food limitation in larval mosquitoes resulted in differences in growth, development, emergence and survival. Larval feeding history also affected oocyst prevalence and intensity in adult mosquitoes, and parasite replication rate within the oocysts. However, ultimate prevalence of sporozoites (the transmissible stages of the parasite) were unaffected by larval food treatment, indicating complex interactions between body condition and within-host parasite dynamics. Overall, our results indicate diverse effects of larval condition on individual traits that combine to determine vectorial capacity. These results support the need to consider environmental variation to better understand malaria transmission  dynamics.