Twenty years of ungulate disease surveillance by the Canadian Wildlife Health Cooperative (2003-2022)

Free-ranging wild ungulates are integral to the health and well-being of Canadian socioecological systems, contributing various One Health benefits (e.g., nutrient cycling, sustainable food resources) to the people and other animals that coexist with them. In North America, ungulates face a range of threats to their population health. To address knowledge gaps surrounding the health of Canadian ungulates, we conducted a retrospective analysis of 20 years of ungulate morbidity and mortality data collected through passive disease surveillance conducted by the Canadian Wildlife Health Cooperative (CWHC) and through submissions from collaborative partners. In total, 2525 cases across 12 species were assigned a category of diagnosis (COD) by a CWHC veterinary pathologist. Infectious/ inflammatory/ transmissible CODs accounted for 53.0% of all cases, with two diagnoses made most frequently: chronic wasting disease (CWD) and Parelaphostrongylus tenuis (P. tenuis) infection. We identified a significant increase in the proportion of cervid cases diagnosed with CWD in Saskatchewan that was consistent across species, with the odds of an individual cervid in Saskatchewan being CWD positive increasing by 22% per year. We also detected a significant increase in the proportion of moose (Alces americanus) cases diagnosed with P. tenuis, and this trend was consistent across endemic regions in Canada. Emerging diseases were also detected for the first time through our surveillance approach (e.g., the first Ontario cases of epizootic hemorrhagic disease virus, detected in white-tailed deer (Odocoileus virginianus)). Trauma (15.3%) and emaciation (8.9%) were the most frequently assigned non-infectious CODs. We highlight potential disease threats to SAR that may emerge secondary to changing distributions of sympatric ungulate species and the pathogens they carry (e.g., CWD positive deer/elk within known caribou ranges in Saskatchewan). Our results highlight the strengths of passive disease surveillance, as well as the need for an integrated, holistic wildlife surveillance approach in Canada.