Larval nutrition affects the capacity of mosquitoes to vector malaria by shaping adult life-history traits

Many adult life history traits in holometabolous insects can be shaped by larval environment. Yet, relatively little work has been done on how changes in larval ecology can influence host-parasite interactions in adult disease vectors. We used Anopheles stephensi mosquitoes and two malaria parasites (Plasmodium yoelii, a rodent malaria, and Plasmodium falciparum, a human malaria) to investigate whether quality of larval habitat influenced vectorial capacity of adult mosquitoes. Larvae were reared under two dietary conditions; one group received a diet commonly used for colony maintenance while the other group received a reduced food diet. Upon emergence, adults were provided an infectious blood feed. We assessed the effects of diet on a range of larval and adult traits including larval development times, number of emerging adults, size upon emergence, larval and adult survival, gonotrophic cycle length, and mating success.  We also estimated the effects of diet on parasite infection rates, growth kinetics, and extrinsic incubation period. Feeding regime affected rates of larval growth, development and emergence, as well as measures of adult reproduction and survival. Feeding regime also affected the intensity of initial Plasmodium infection (oocyst stage) and parasite replication, but without differences in overall infection prevalence at either the oocyst or sporozoite stage. The combined effects led to a relative reduction in vectorial capacity (a measure of the transmission potential of a mosquito population) in the low food treatment of 70%. These results highlight the need to consider environmental variation at the larval stages to better understand malaria transmission dynamics.