Divergent pathogenesis and transmission among avian and mammalian isolates of highly pathogenic avian influenza A (H5N1) in swine

Authors: Arruda, Bailey; Baker, Amy; Buckley, Alexandra; Anderson, Tavis; TORACHETTI, MIA - Diagnostic Virology Laboratory/ National Veterinary Services Laboratories; HINES BERGESON, NICHOLE - Diagnostic Virology Laboratory/ National Veterinary Services Laboratories; KILLIAN, MARY - Diagnostic Virology Laboratory/ National Veterinary Services Laboratories; LANTZ, KRISTINA - Diagnostic Virology Laboratory/ National Veterinary Services Laboratories

Submitted to: Meeting Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 2/26/2024
Publication Date: N/A
Citation: N/A

Interpretive Summary: Highly pathogenic avian influenza (HPAI) viruses have potential to cross species barriers and cause pandemics in humans. Since 2022, H5N1 HPAI has infected poultry, wild birds, and mammals across North America. Continued circulation in birds and infection of multiple mammalian species with strains possessing mammalian adaptation mutations increase the risk of infection and subsequent exchange of viral genes with influenza A viruses (IAV) endemic in swine. This exchange of genes increases the risk of transmission within and between swine holdings. We assessed the susceptibility of swine to avian and mammalian H5N1 HPAI strains using a pathogenesis and transmission model. All strains replicated in the lower respiratory tract of pigs and caused lesions in the respiratory tract consistent with IAV. Viral replication in the nasal cavity, transmission to contact pigs, lesions in the lung at the cellular level, and viral distribution within the lung of mammalian isolates suggested potential mammalian binding adaptation. Mammalian adaptation and exchange of viral genes with IAV endemic in swine may increase the risk of incursion and transmission of HPAI in feral, backyard, or commercial swine. However, the risk is low in confinement operations with industry standard biosecurity. Bird proofing feed and facilities and not using untreated surface or well water that may be contaminated with wild waterfowl feces would be prudent to further reduce this risk.

Technical Abstract: Highly pathogenic avian influenza (HPAI) viruses have potential to cross species barriers and cause pandemics in humans. Since 2022, H5N1 HPAI has infected poultry, wild birds, and mammals across North America. Continued circulation in birds and infection of multiple mammalian species with strains possessing mammalian adaptation mutations increase the risk of infection and subsequent exchange of viral genes with influenza A viruses (IAV) endemic in swine. This exchange of genes increases the risk of transmission within and between swine holdings. We assessed the susceptibility of swine to avian and mammalian H5N1 HPAI strains using a pathogenesis and transmission model. All strains replicated in the lower respiratory tract of pigs and caused lesions in the respiratory tract consistent with IAV. Viral replication in the nasal cavity, transmission to contact pigs, lesions in the lung at the cellular level, and viral distribution within the lung of mammalian isolates suggested potential mammalian binding adaptation. Mammalian adaptation and exchange of viral genes with IAV endemic in swine may increase the risk of incursion and transmission of HPAI in feral, backyard, or commercial swine. However, the risk is low in confinement operations with industry standard biosecurity. Bird proofing feed and facilities and not using untreated surface or well water that may be contaminated with wild waterfowl feces would be prudent to further reduce this risk.