Whole-Genome Sequence of Cervid atadenovirus A from the Initial Cases of an Adenovirus Hemorrhagic Disease Epizootic of Black-Tailed Deer in Canada

Adenoviral hemorrhagic disease in a farmed elk (Cervus canadensis) in Alberta, Canada

Adenoviral hemorrhagic disease (AHD), caused by deer atadenovirus A (OdAdV-1), affects captive and free-ranging cervids across North America. Here we present a case of AHD in a 6-month-old female elk calf from a farm in Alberta. Histopathology revealed multisystemic vasculitis with endothelial intranuclear inclusion bodies, pulmonary hemorrhage, and small intestinal hemorrhage characteristic of the acute systemic form of AHD. Immunohistochemistry was positive for OdAdV-1, confirming the diagnosis. Whole-genome sequencing of the virus was conducted for phylogenetic comparison. This is the 1st reported case of AHD in a farmed elk in Canada and the 1st reported case in an elk in Alberta. Key clinical message: Adenoviral hemorrhagic disease (AHD) is an emerging disease that should be investigated as a top differential when diagnosticians and veterinarians encounter young cervids found dead with pulmonary edema or hemorrhage and/or hemorrhagic enteropathy.

Divergent SARS-CoV-2 variant emerges in white-tailed deer with deer-to-human transmission

Wildlife reservoirs of broad-host-range viruses have the potential to enable evolution of viral variants that can emerge to infect humans. In North America, there is phylogenomic evidence of continual transmission of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) from humans to white-tailed deer (Odocoileus virginianus) through unknown means, but no evidence of transmission from deer to humans. We carried out an observational surveillance study in Ontario, Canada during November and December 2021 (n = 300 deer) and identified a highly divergent lineage of SARS-CoV-2 in white-tailed deer (B.1.641). This lineage is one of the most divergent SARS-CoV-2 lineages identified so far, with 76 mutations (including 37 previously associated with non-human mammalian hosts). From a set of five complete and two partial deer-derived viral genomes we applied phylogenomic, recombination, selection and mutation spectrum analyses, which provided evidence for evolution and transmission in deer and a shared ancestry with mink-derived virus. Our analysis also revealed an epidemiologically linked human infection. Taken together, our findings provide evidence for sustained evolution of SARS-CoV-2 in white-tailed deer and of deer-to-human transmission.