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The Public Health Risks of Three Potentially Zoonotic Viruses in Pigs and Pork in Canada

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Title: The Public Health Risks of Three Potentially Zoonotic Viruses in Pigs and Pork in Canada
Author: Wilhelm, Barbara
Department: Department of Population Medicine
Program: Population Medicine
Advisor: McEwen, Scott A.
Abstract: The research described in this thesis aims to describe the potential public health risks posed by three emerging and potentially zoonotic viruses (hepatitis E virus (HEV), Norovirus (NoV), and rotavirus (RV) in pigs and pork in Canada. This was investigated via a scoping review, surveys of Canadian pigs and retail pork, and compilation of a risk profile for HEV, the virus for which the resulting dataset was most complete. A scoping review was conducted to summarize the relevant published literature. A small number of published zoonotic cases (HEV n=3, NoV = 0, RV = 40 (zoonoses = 3; human-animal re- assortants = 37)) were categorized as ‘likely’ zoonoses. A survey of Canadian retail pork chops and pork livers was conducted using the Canadian Integrated Program for Antimicrobial Resistance Surveillance (CIPARS) sampling platform. Overall, HEV prevalence on retail pork was comparable with other published reports. Prevalence of E. coli, Salmonella spp., and Campylobacter spp. was significantly greater than HEV, NoV or RV on our retail pork samples. Sample type (pork chop vs. liver) was a significant predictor for HEV detection using exact logistic regression modeling. A survey of Canadian finisher pigs was conducted for detection of the three viruses of interest, using the CIPARS and FoodNet Canada on-farm sampling platforms. Seventy-two herds were sampled. HEV was detected in 30/88 farms (34.1% (95% CI 25.0%, 44.5%)); PEC in 18 (20.5% (95% CI 13.4%, 30.0%)), and RV in six farms (86.0% (CI 3.2%, 14.1%)). Viral prevalence varied with province and sampling platform. Requiring shower-in and providing boots for visitors were significant predictors (P < 0.05) in single fixed effect mixed logistic regression analysis for detection of HEV and PEC, respectively. Obtaining feeder pigs from multiple sources was consistently associated with greater odds of viral detection. A risk profile for HEV in pigs or pork in Canada was compiled. Risk categories (high/medium/low) for acquiring clinical Hepatitis E from exposure to pigs or pork were drafted, and the proportion of the Canadian population at high risk from either exposure is hypothesized to be relatively small.
Date: 2016-05
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