Research

Our research focusses on insect vectors (mainly mosquitoes and biting midges) in four main lines of research:

1. Thermal ecology

Temperature strongly influences basic life parameters of insect vectors, such as larval and adult development, but also all insect/pathogen-related factors. Thus, the intensity of pathogen transmission (vector capacity) by insects is strongly temperature dependent, but very little is known about the thermal preferences of major insect vectors. We are studying the preferred temperatures of different life stages (larvae, adults), feeding stages (blood-fed, sugar-fed), behaviour (oviposition, resting, host-seeking) and after immune challenge (infection by virus or filariae; microinjection of Sephadex beads or bacteria) of mosquitoes and biting midges. The investigations include laboratory (temperature gradient setup with controlled humidity and video tracking system), semi-field (large outdoor cages providing different microclimates) and field experiments (along gradients at different altitudes). Our data will contribute to improve models of insect vector distribution and vector-borne disease outbreaks which is especially important in the wake of climate change.

2. Vector competence

The impact of insect-borne diseases is increasing, also in Europe. Our group has a long history of performing vector competence experiments, i.e., exposing insects (from laboratory colonies or collected in the field) to blood meals spiked with pathogens and analysing them (saliva, body parts) for the presence of pathogens after an incubation period. These experiments are performed in a laboratory of biosafety level 3. The results of these studies serve as a basis for risk assessment for local transmission of emerging pathogens.

For the mosquito-transmitted Japanese encephalitis virus, direct transmission between pigs has recently been described under laboratory conditions. In addition to studies on the vector competence of abundant mosquito species from Switzerland for two JEV strains, we explore whether series of single-host cycles (either in porcine or insect cells) result in virus adaptions leading to altered virus fitness and transmissibility. This will yield fundamental insights into viral requirements for dual-host capacity of Flaviviruses.

3. Novel control options

Insect vectors are attracted to hosts by carbon dioxide released in their breath and by their body odours which are mainly produced by the skin microbiota. Differences in attractiveness between human individuals to mosquitoes is mediated by these volatiles released from the skin. A novel solution for protection against insect vectors could be achieved by manipulating the skin microbiota. In laboratory experiments with olfactometers, we are investigating the attractiveness of volatiles collected from individuals (humans, different sheep breeds) or from skin microbiota (bacteria, fungi) cultivated on various agar media (sweat, sheep blood) for insect vectors. Ultimately, microbial-based repellents could be devised which might offer long-lasting protection to humans as well as animals.   

Volatile pyrethroids, acting as spatial repellents, can create a vector-free environment, and they have been shown to be effective against mosquitoes, by reducing their house entry and biting, even outdoors. We are evaluating the effect of such pyrethroid spatial repellents and of natural compounds on biting midges in high-throughput assays in the laboratory and under (semi-)field conditions. Spatial repellents could be an effective option for shielding animals against biting midges, against which currently no effective measures exist.

4. Monitoring of insect vectors and circulating pathogens

Monitoring of insect vectors is continuously being done in the frame of ongoing research projects, using a variety of trap types. The insects are identified by using specifically designed, simplified morphological keys or by molecular methods (DNA- or protein-based), allowing for their accurate, rapid and cost-efficient identification.

Novel tools for monitoring circulating pathogens include the detection of antibodies in vector blood meals with a developed pan-specific ELISA (to detect antibodies of mammalian and bird hosts; ‘xenosurveillance’). Further, pathogens can be detected by molecular means on sugar-impregnated FTA cards onto which vectors deposit saliva when captured in traps. These methods can be additional surveillance tools, especially when sampling potential animal reservoirs is difficult.