Transmission dynamics of highly pathogenic avian influenza virus at the wildlife-poultry-environmental interface: A case study

Avian influenza viruses (AIVs) regularly circulate between wild and domestic bird populations, with highly pathogenic AIVs (HPAIV) raising growing concern. While HPAIV transmission among domestic birds, wildlife, and the environment is recognized, little is known about persistence and spillover/spillback at these interfaces. We integrated test results from samples collected on and around an infected poultry premise (IP) where H5N1 HPAIV was confirmed in a poultry flock in 2022 in Southern Ontario, Canada, to investigate AIV transmission in wildlife and the environment. Samples were taken from a captive flock of Mallards (Anas platyrhynchos) on site, sediment from water bodies on site, and wildlife samples collected within a 100km radius of the IP. Serologic evidence indicated H5 exposure in the captive mallards, despite no observed morbidity or mortality or positive PCR detections across two sampling points. Genetic material from the same H5N1 HPAIV subtype circulating in the domestic birds and from low pathogenicity avian influenza viruses were detected in wetlands on site. Surveillance of live birds and sick/dead wildlife conducted within a 100km radius confirmed that the virus circulated in wildlife before and after IP confirmation. These results reinforce that biosecurity remains the most critical aspect of minimising spillover/back risk in a virus that has been shown to circulate in asymptomatic wild birds and persist in the surrounding environment.

Jolene A. Giacinti1, Madeline Jarvis-Cross2, Hannah Lewis3, Jennifer F. Provencher1, Yohannes Berhane4, Kevin Kuchinski5, Claire M. Jardine6, Anthony Signore4, Sarah C Mansour5, Denby E. Sadler3, Brian Stevens6, Natalie A. Prystajecky5,7, Sailendra N. Sarma1, Davor Ojkic8, Gabrielle Angelo P Cortez5, Marzieh Kalhor5, Ethan Kenmuir5, Christopher M. Sharp3 1Ecotoxicology and Wildlife Health Division, Science and Technology Branch, Environment and Climate Change Canada, Government of Canada, Ottawa, Ontario, Canada 2Department of Ecology and Evolutionary Biology, University of Toronto 3Ontario Region Wildlife and Habitat Assessment Section, Canadian Wildlife Service, Environment and Climate Change Canada, Government of Canada, Ottawa, Ontario, Canada 4National Centre for Foreign Animal Disease, Canadian Food Inspection Agency, Government of Canada, Winnipeg, Manitoba, Canada 5Department of Pathology and Laboratory Medicine, University of British Columbia, Vancouver, British Columbia, Canada 6Canadian Wildlife Health Cooperative, Department of Pathobiology, Ontario Veterinary College, University of Guelph, Guelph, Ontario, Canada 7Public Health Laboratory, British Columbia Centre for Disease Control, Vancouver, British Columbia, Canada 8Animal Health Laboratory, University of Guelph, Guelph, Ontario, Canada

Notable outbreaks, field and molecular epidemiology, and surveillance in wild birds