The role of mosquito behaviour on parasite transmission

I use a combination of theory and experiments to explore the role of various aspects of mosquito behaviour on the ability of mosquitoes to transmit parasites. Special focus is given to the mosquito Anopheles gambiae s.s., the principal vector for Plasmodium falciparum, a parasite that causes human malaria. Female mosquitoes require host blood for egg production, but also use sugar from nectar sources; however, the extent of sugar use is poorly understood. Sugar can be used to fuel somatic maintenance and activity. Blood, on the other hand, is a poor resource for fueling somatic maintenance and activity because of its low conversion efficiency to energy reserves. Furthermore, although blood is necessary for egg production, obtaining blood is risky. Thus, there is a trade-off between reproduction and survival when using these two resources. I use an energy-explicit dynamic state variable model where the availability of both blood and sugar is varied and ask whether energetic condition is important for the feeding choices of mosquitoes. I then test this theory using two independent behavioural bioassay experiments. Both the experiments and theory agree that energetic state will have an impact on mosquito behavior – mosquitoes with lower reserves choose sugar over blood, and the availability of blood and sugar have non-linear effects on these choices. Furthermore, I examine the evolution of egg-laying behavior in the context of a co-evolving complex of adult and larval traits and find that adult mosquitoes evolve very specific preferences for habitats that correspond to larval characteristics, but that adults try to minimize larval interactions. Lastly, I use well established metrics of parasite transmission ability to demonstrate that the availability of both blood and sugar have a large impact on the ability of a mosquito population to transmit parasites. The availability of sugar in the environment may thus play a larger role in a mosquito‟s life, and subsequently its ability to transmit parasites, than traditionally thought. I discuss this finding in light of current vector control strategies.