Abstract : Several rodent species exhibit cyclic variations of their population densities. These demographic cycles, by increasing contacts between humans and animals, can influence the emergence of zoonoses. This thesis takes part in conservation medicine. This approach aims to study human health by considering also animal health and ecosystem dynamics. In this context, I studied a community of parasites found in a community of cyclic rodents to identify the reservoirs of zoonosis agents and the parasites, which may have a role in rodent demographic cycles. I focused on a rodent community including the fossorial water voles, the common voles, the bank voles, the yellow necked mice and the wood mice in Franche-Comté (East of France). The results and the epizootiologic surveys presented here bring insights into the biotic and abiotic risks associated with emergence of zoonoses.
Three zoonosis agents were detected: two hantaviruses (Puumala virus and Tula virus) and Cowpox virus. Host dispersal and social behaviour are important for the transmission of the specific hantaviruses and of the non specific Cowpox virus. These viruses are principally detected in forest area. Rodents from forested areas present a different parasite community from rodents found in meadows. Infestations with helminths are more frequent in meadows than in forest. An immunogenetic study revealed susceptibility or resistance alleles for viral infections. Helminths and mites could also have a protective or an enhancing role in viral infections. One of these helminths could have a role in its host dynamics. Using experimental work and modelling, I demonstrate the impact of the non specific nematode T. arvicolae on common vole fecundity and its regulator role for arvicoline populations.
This thesis provides essential knowledge to evaluate the importance of biodiversity and community ecology in the management of human zoonosis risk factors.