| Summary: | Toxoplasma gondii is one of the most successful parasites in the world and can have serious adverse effects on immunocompromised individuals and foetuses. It is thus a parasite of public health concern, especially in the Canadian North where seroprevalence in some Inuit communities is much higher than in other parts of North America. Food-borne transmission is likely a significant route of transmission among northern residents as well as Arctic carnivores, where transmission may be altered by the rapid demographic and environmental changes affecting Arctic and subarctic regions. I focused on lynx as the only definitive host that can produce oocysts in subarctic regions, and foxes as intermediate hosts at high risk of exposure. The aim of this research was first to assess T. gondii exposure, prevalence and genetic diversity in foxes and lynx in northern Canada. I hypothesized that foxes would act as good sentinel species for T. gondii in the North since they occupy a high trophic position in the Arctic and are widespread in northern Canada. I also sought to determine if lynx are serving as definitive hosts for T. gondii using DNA based methods (real time PCR with melting-curve analysis) which are more sensitive than efforts to detect oocysts in feces. I used a sequence specific magnetic capture DNA extraction and real-time PCR to test whole hearts and brains of foxes and lynx. I tested samples serologically by enzyme-linked immunosorbent assay (ELISA) using fluids from thawed hearts. I targeted foxes from all four Inuit regions of Canada: Inuvialuit Settlement Region in Canada’s Western Arctic, Nunavut, Nunavik in northern Québec, and Nunatsiavut in Labrador. Exposure and tissue infection were lower in fox and lynx in Canada’s Western Arctic, and higher in the Eastern Arctic, especially the Hudson Bay region of Nunavik. These results are compatible with recent serological findings in people from Inuit Health Surveys, supporting the hypothesis that fox are indeed suitable sentinels of environmental transmission ...
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