Toxoplasma gondii in wildlife traditionnally harvested by Inuit of Nunavik, Canada

Abstract

For centuries, Inuit have consumed wildlife. For decades, high levels of Inuit exposure to Toxoplasma gondii have been reported in Nunavik, Canada. This is puzzling given the rare occurrence of felids, the only definitive host for T. gondii, throughout this region. The handling and/or consumption of wildlife, more particularly the consumption of raw tissues, have been identified as risk factors for T. gondii exposure in Inuit. Yet, little is known about wildlife as reservoirs for T. gondii throughout Nunavik, largely due to lack of a sensitive direct detection method needed for a large-scale study. The rationale for this thesis was to determine whether wildlife poses a risk for Inuit exposure to T. gondii in Nunavik. This thesis first set out to confirm whether the magnetic capture and real-time PCR technique can be used to detect DNA of T. gondii in wildlife by assessing the PCR prevalence in tissues of foxes trapped throughout Nunavik. Then, seroprevalence (MAT) and PCR prevalence (MC-PCR) of T. gondii were compared in ringed seals, geese, ptarmigan and caribou to determine whether serological results can predict an animal’s infection status. The probability that Inuit are exposed to T. gondii through consumption of goose tissues was then estimated in a quantitative exposure assessment. Lastly, we determined whether Inuit awareness, knowledge and risk perceptions ofparasites in wildlife influence the adoption of health-protective behaviors that mitigate exposure to foodborne parasites based on multivariable logistic regression analysis. DNA of T. gondii was detected in 44% (95% CI: 28-60%) of foxes from four locations in Nunavik. DNA of T. gondii was also detected in 9% (CI: 3-15%) of geese, but not in other wildlife species including 20% (95% CI: 12-31%) of ringed seals and 26% (95% CI: 14-43%) of caribou seropositive on MAT. In geese, parasite load was quantified as highest in heart, followed by brain, breast muscle, liver, and gizzard. Overall, given the consumption of 4 goose tissues, there was a 32% probability that Inuit were exposed to at least 1 bradyzoite during a one month period. Finally, approximately 61% (95% CI: 53-69%) of Inuit were aware of parasites and 47% (95% CI: 39-56%) were knowledgeable about their transmission. Both perceived severity and response efficacy positively influenced the adoption of health-protective behaviors. This is the first account of T. gondii detection in wildlife using the MC-PCR technique. In Nunavik, foxes are a good sentinel for T. gondii. Wild geese harbor the parasite and hunter-harvested geese are a plausible source of T. gondii, although the probability of exposure is low based on consumer data collected during this thesis. Risk communication messages should provide information on specific zoonotic parasites, as well as remind people that cooking their meat above 67ºC is effective at reducing their probability of exposure. An alternative, perhaps more culturally-appropriate means of inactivating the parasite could be by freezing at -12º C or colder for 3 days. Future research is needed to validate the use of serological assays in wildlife as a screening tool for food safety decision-making. For now, it is not recommended to extrapolate serological results on the infection status of individual animals for wildlife species included in this thesis. Future research is also needed to identify whether other wildlife species consumed by Inuit are infected with T. gondii including other migratory birds potentially highly exposed in the south.