State-dependent domicile leaving rates in Anopheles gambiae


Background Transmission of Plasmodium greatly depends on the foraging behaviour of its mosquito vector (Anopheles spp.). The accessibility of blood hosts and availability of plant sugar (i.e., nectar) sources, together with mosquito energy state, have been shown to modulate blood feeding (and thus biting rates) of anopheline mosquitoes. In this study, the influence of mosquito starvation status and availability of nectar on the decision of female Anopheles gambiae mosquitoes to leave a bed net-protected blood host was examined. Methods Two small-scale mesocosm experiments were conducted using female mosquitoes starved for 0, 24 or 48 hours, that were released inside a specially constructed hut with mesh-sealed exits and containing a bed net-protected human volunteer. Floral cues were positioned on one side of the hut or the other. Several exponential decay models were developed that characterized the emigration rates from the huts. These model fits were evaluated by examining their fitted parameter estimates, comparing Akaike Information Criterion (AIC) scores. Results Starved mosquitoes left domiciles at a higher rate than recently fed individuals however, there was no difference between one-day and two-day-starved mosquitoes. There was also no effect of floral cue placement on mosquito emigration rates. The best fitting emigration model was one based on both mosquito energy state and time whereas the worst fitting model was one based on the assumption of constant leaving rates, independent of time and energy state. Conclusions The results confirm that mosquito-leaving behaviour is energy-state dependent, and provide some of the first evidence state-dependent domicile emigration in An. gambiae, which may play a role in malarial transmission dynamics.

Malaria Journal