Influenza A Viruses in North American Wild Birds

Zijing Cao, a student from The City University of New York – Hunter College, worked with Dr. Rebecca Poulson on influenza A virus in North American wild birds.

Abstract: The emergence of highly pathogenic (HP) H5N1 avian influenza in North American wild birds in 2021 has posed significant threats to many species. Understanding the landscape of influenza A viruses (IAV) in wild bird populations is crucial for effective disease management and prevention. This project focused on the population immune response to H5N1 IAV, specifically in modulating infection and disease outcomes. Blue-winged teal (BWTE; Spatula discors) from the Mississippi flyway in North America were sampled for the study. The prevalence and severity of IAV infections in wild birds are hypothesized to be influenced by host immunity, particularly the presence of antibodies targeting HP H5 IAV. Serologic techniques used here included bELISA (previous exposure to IAV), HI (H5 antibodies), MN (H5 functional neutralizing antibodies), and ELLA (N1 antibodies). Between 2017-2019, BWTE showed a high IAV exposure rate (50-70%) based on bELISA and throughout the ongoing HP H5 IAV outbreak (spring and fall, 2022; spring 2023). Positive sera were further examined to determine their response to H5 or N1 antigen. HI indicated no H5 responses, while MN showed a slight (10-20%) response. ELLA revealed a high N1 antibody response (50-70%). The presence of H5 antibodies in bELISA positive samples was relatively low initially, but there was an increase in H5 antibody response between 2022-2023, likely in response to the introduction of HP H5. During the outbreak, the observed response in the BWTE population indicates survival and immunity development, making it an excellent model for identifying avian populations at risk.