The GsGd lineage (A/goose/Guangdong/1/1996) H5N1 virus was introduced to Canada in 2021/2022 through the Atlantic and East Asia-Australasia/Pacific flyways by migratory birds. This was followed by unprecedented outbreaks affecting domestic and wild birds, with spillover into other animals. Here, we report sporadic cases of H5N1 in 40 free-living mesocarnivore species such as red foxes, striped skunks, and mink in Canada. The clinical presentations of the disease in mesocarnivores were consistent with central nervous system infection. This was supported by the presence of microscopic lesions and the presence of abundant IAV antigen by immunohistochemistry. Some red foxes that survived clinical infection developed anti-H5N1 antibodies. Phylogenetically, the H5N1 viruses from the mesocarnivore species belonged to clade 2.3.4.4b and had four different genome constellation patterns. The first group of viruses had wholly Eurasian (EA) genome segments. The other three groups were reassortant viruses containing genome segments derived from both North American (NAm) and EA influenza A viruses. Almost 17 percent of the H5N1 viruses had mammalian adaptive mutations (E627 K, E627V and D701N) in the polymerase basic protein 2 (PB2) subunit of the RNA polymerase complex. Other mutations that may favour adaptation to mammalian hosts were also present in other internal gene segments. The detection of these critical mutations in a large number of mammals within short duration after virus introduction inevitably highlights the need for continually monitoring and assessing mammalian-origin H5N1 clade 2.3.4.4b viruses for adaptive mutations, which potentially can facilitate virus replication, horizontal transmission and posing pandemic risks for humans.

The detrimental effects of West Nile virus (WNV) have been well characterized in several taxonomic groups of North American birds, such as corvids and raptors. Relatively less is known about the virus' effects in waterfowl species, many of which are abundant in North America and occupy habitats, for example wetlands and marshes, likely to harbour dense mosquito populations. In two successive years, outbreaks of WNV-associated disease were observed in waterfowl at a rehabilitation centre. In the present report, clinical and pathological findings are provided for seven mallards (Anas platyrhynchos) and one Canada goose (Branta canadensis) that developed acute disease and either died or were killed humanely. The most severe and consistent microscopic lesion in mallards was myocardial degeneration and coagulative necrosis consistent with acute heart failure. The Canada goose had necrotizing myocarditis. Other lesions included pulmonary perivascular oedema, lymphoplasmacytic hepatitis, and splenic and bursal lymphoid depletion. WNV infection was confirmed using reverse transcriptase-polymerase chain reaction and immunohistochemical staining. Myofibres within all cardiac muscle layers had positive immunohistochemical staining, as did blood vessel walls in the heart and spleen. These results suggest that juvenile mallards are highly susceptible to fatal WNV-associated cardiac failure, and confirm that adult Canada geese are susceptible to fatal WNV-associated disease. The synchronous timing of clinical disease and death in these waterfowl are consistent with WNV mosquito-borne infections within a WNV transmission focus during the summer (July and August) of 2012 and 2013.

The majority of graduates from veterinary schools in the United States and Canada join companion-animal practices. In most schools, their clinical learning and client interaction experiences occurred primarily in referral teaching hospitals. These specialty hospitals play an essential role in the veterinary care continuum by providing advanced training, clinically-based research, and sophisticated diagnostics and procedures. However, they are not ideal as the principal setting for preparing veterinarians to bring value to the primary health care practices that they join. A new model for companion-animal primary health care education and service delivery has been developed at the Ontario Veterinary College, University of Guelph. The nine integrated programs, which have defined learning objectives and outcome assessments, include communication, nutrition, rehabilitation, behavior, welfare, One Health (ecosystem approach to health), preventive and general medicine, good citizenship, and research. The learning experience begins with first-year student veterinarians and takes place in a practice setting with paying clients from the community. Significantly, the students are learning in an environment that emphasizes the importance of the client experience, teamwork, and practice management while ensuring quality health care for patients. The future of companion-animal primary health care and the optimal preparation of veterinarians are critical issues for the veterinary colleges and profession. Enhanced research into new models for primary health care education and service delivery is urgently needed.

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