Surveillance of Highly Pathogenic Avian Influenza Virus in Wild Canids from Pennsylvania, USA

While wild canids are known to develop severe disease when infected with the H5N1 highly pathogenic avian influenza virus (HPAIV) clade 2.3.4.4b, infection and mortality are sporadic and typically involve individual animals. Interpretation of sporadic mortality events is challenging due to the lack of knowledge on H5N1 HPAIV ecology in wild canids and limited active surveillance data on viral infection, transmission, and/or exposure. In this study, we summarize the diagnostic data for wild canids from Pennsylvania who died and were tested for HPAIV during 2021–2024. In addition, we report serologic data from wild canids that were tested for exposure to the influenza A virus (IAV). Collectively, these data suggest that wild canids (especially young red foxes) are susceptible to H5N1 HPAIV clade 2.3.4.4b and infection can result in severe disease; however, IAV exposure in wild canids in Pennsylvania seems to be rare. None of the opportunistically collected animals tested positive for antibodies consistent with previous infection with H5N1 HPAIV. Targeting canids at increased risk of infection (e.g., those exposed to wild waterfowl or located in an area of an active outbreak in wild or domestic animals) may yield a higher seroprevalence.