Role of the chemosensory receptors in the domiciliation process of Chagas disease vectors : case of Rhodnius species
Triatominae are hematophagous bugs that are vectors of Trypanosoma cruzi, the causative agent of Chagas disease, endemic in Latin America. In the wild, Rhodnius species mainly infested palms and feed on a wide range of vertebrate hosts that find refuge in this habitat. However, some Rhodnius species have left their natural habitat (sylvatic habitat) to come into close contact with humans, colonizing their homes, and potentially transmitting T. cruzi to humans. The process of domiciliation describes the transition of bugs from the sylvatic to the anthropised environment. For some species, domiciliation appears as a one-way process. Thus R. prolixus is described as almost exclusively domiciliary. Other species are considered to be in the process of domiciliation, some populations living in a sylvatic environment and others in an anthropised one. However, the domiciliation process does not seem to occur for all species. Some species visit sporadically the dwellings but do not remain there, others seem exclusively sylvatic. Different population genetic studies have shown that domiciliary and sylvatic bug populations of the same geographic area are genetically differentiated and that domiciliary populations result from one or more founder effects from sylvatic habitats. In homes, bugs find very favorable conditions for their development. Environmental conditions are buffered, and food resources are assured. This domiciliation process involves change of habitat and host, the main source of food in the houses being human. Our hypothesis is that this domiciliation process involves the chemosensory system, a system that allows organisms to interact with their environment. The chemosensory genes belong to multigene families whose evolutionary dynamics are rapid and at the origin of changes in sensory sensitivity. These changes could be involved in the adaptation to a new environment, in this case the domiciliary environment for blood-sucking bugs.