Host antiviral responses and tissue distribution of Highly Pathogenic Avian Influenza A (HPAI) Clade 2.3.4.4b isolates in wild waterfowl

To assess the role of alternate avian hosts in spread of highly pathogenic avian influenza strains, challenge and transmission studies were performed with three distinct 2.3.4.4b clades of HPAI virus; a wholly Eurasian H5N5, a North American reassorted H5N1 and a North American reassorted H5N1 strain with a mammalian adaptive mutation in PB2-627K. The latter isolate, linked to outbreaks in 14 poultry farms in Quebec City, also had changes in other virulence factors, including PB1-F2 and NS1 known to impair innate immunity. It is not known whether these viruses elicit innate immunity in these alternate hosts that may play a role in long-distance transmission of viruses. Here we examine viral tissue tropism and innate immune responses in Blue-Winged Teal (Spatula discors) and Canada Geese (Branta canadensis). To examine expression of key interferon stimulated genes (ISGs) in these species, we performed RT-qPCR on six tissues from infected birds - duodenum, cecal tonsil, trachea, lung, brain, and spleen. Viral load and innate immune gene expression was highest in brain of H5N5 infected teals, and all tissues of the H5N1 PB1-F2-627K infected teals. Notably, the H5N1 (PB2-627K) was less pathogenic to teals, while all three viruses were equally pathogenic to Canada geese. Understanding how different waterfowl species respond to the current clades and how the virus spreads is crucial for minimizing impacts on wildlife, public health, and the further risk of transmission to domestic poultry.

Vagif Seyid1, Renald J. Legaspi, Ximena Fleming-Canepa1, Tamiru Alkie3, Frank Baldwin4, Yohannes Berhane3 and Katharine Magor1,2 1Department of Biological Sciences, University of Alberta, Edmonton, AB and 2Li Ka Shing Institute of Virology, Edmonton, Alberta, Canada 3National Centre for Foreign Animal Disease, Canadian Food Inspection Agency, Winnipeg, Manitoba, Canada 4Canadian Wildlife Service, Environment and Climate Change Canada / Government of Canada

Transmission pathways, pathobiology, immune responses