Microclimate selection strategies of mosquito disease vectors

Mosquitoes transmit pathogens that can cause disease in humans and animals like dengue fever, malaria and heartworm infections. In Switzerland, the first detection of West Nile virus and the expansion of the tiger mosquito Ae. albopictus highlight the importance of adequate risk models. Because mosquitoes are ectotherms, meteorological factors and especially temperature will directly affect their fitness, population dynamics and their capacity to transmit pathogens (vector competence). Mosquito-borne disease models, however, normally do not consider that mosquitoes live in a heterogenous landscape and can choose their microhabitat. We earlier showed that mosquitoes evade unfavourable temperatures through microhabitat selection, however, the effects on fitness and vector competence have not been addressed. In addition, it is still unclear how mosquitoes navigate these preferred microhabitats under natural conditions.We propose to study both the behavioural mechanism of microhabitat selection and its effect on the mosquito's fitness and vector competence. For this, we will study microhabitat selection both in simulated natural microclimates and in various controlled laboratory and semi-field settings. In all experimental systems, we will study behavioural responses to the various environmental conditions using our cutting-edge multicamera videography systems.To unravel the behavioural mechanisms of microhabitat selection, we will combine two sets of experiments. 1) First, we will identify how flying mosquitoes respond to both preferred and unpreferred air temperatures. For this, we will both track in detail the 3D movements of flying mosquitoes and characterize the 3D fluid dynamics of heat plumes at various temperatures. Here, we will use our high-fidelity multicamera videography systems to track the mosquito body and wing movements in 3D at high spatial and temporal resolution, and we will characterize the 3D heat plume using a combination of stereoscopic Schlieren imaging and numerical simulations. 2) To test how mosquitoes adapt this microhabitat selection behaviour, we will perform real-time 3D video-based mosquito tracking in a 2x2x2 m large cage setup with variable background temperature and humidity. Using a comparative research approach, we will compare the responses between tropical and temperate mosquitoes, and various temperature-adapted mosquito lines.We will study how environmental conditions affect mosquito survival, fecundity, and vector competence, using a combination of laboratory and outdoor experiments. In the lab setup, under realistic diurnal variations in temperature, humidity and light conditions, we will test how microhabitat availability affects survival and fecundity, and how parasite (Dirofilaria immitis) and virus (dengue virus) infections affect microhabitat selection and thereby vector competence. To determine a potential effect of microhabitat selection, we will perform automatic 3D video-based tracking of mosquitoes in large cages, which will allow us for the first time to determine how mosquitoes move between various microhabitats during the natural diurnal varying conditions. Temperature is one of the key drivers of mosquito-borne diseases. Here, we will generate the essential knowledge to understand mosquito microhabitat selection and the effect on vector competence.