Avian influenza virus prevalence, distribution and pathogen-microbiome interactions in Maine waterfowl

Highly pathogenic avian influenza (HPAI) virus H5N1 (clade 2.3.4.4b) has had unprecedented global impacts on wild and domestic animals, human health, and food security in recent years. More than 10,000 wild birds and 100 million poultry across the US have been impacted since 2022, in addition to increasing cases in cattle, marine mammals, and humans. Waterfowl are the natural reservoirs of avian influenza viruses (AIV) and have primarily served as asymptomatic carriers during previous HPAI outbreaks, rarely showing signs of disease. However, the 2022 outbreak resulted in significant increases in morbidity and mortality, highlighting the need to better understand risk factors of infection in wild birds. Previous studies have indicated microbial communities are critical to host health, impacting longevity, immune response, pathogen defense, and nutrition. Assessing changes in the microbiome could lead to insight on individual immune function and disease transmission. Our project aims to 1) estimate the prevalence and distribution of AIV in Maine waterfowl and 2) examine the relationship between AIV infection and host microbiome. Samples from Mallards, American Black Ducks, Wood Ducks, and Green-winged Teal were collected before (2018-2020; n=496) and after (2023-2024; n=641) the 2022 outbreak for detection and sequencing of AIV strains, as well as for microbiome characterization by 16S rRNA sequencing. We will present preliminary results on the differences observed in host-associated microbial diversity by infection status with respect to the 2022 outbreak. Implications of this work could lead to novel insights on risks associated with transmission and spillover to domestic animals and humans.

Melissa Simon-Ecology and Environmental Sciences, University of Maine, Orono, ME, USA Olivia Choi-Cooperative Extension Diagnostic and Research Laboratory, University of Maine, Orono, ME, USA Kelsey Sullivan-Maine Department of Inland Fisheries and Wildlife, Bangor, ME, USA Robin Dyer-Animal and Plant Health Inspection Service, US Department of Agriculture, Augusta, ME, USA Pauline Kamath-School of Food and Agriculture, University of Maine, Orono, ME, USA

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