Investigation of risk factors for introduction of highly pathogenic avian influenza H5N1 virus onto table egg farms in the United States, 2022: a case–control study

Authors

Alice L. Green, USDA Centers for Epidemiology and Animal Health
Matthew Branan, USDA Centers for Epidemiology and Animal Health
Victoria L. Fields, USDA Centers for Epidemiology and Animal Health
Kelly Patyk, USDA Centers for Epidemiology and Animal Health
Stephanie K. Kolar, USDA Centers for Epidemiology and Animal Health
Andrea Beam, USDA Centers for Epidemiology and Animal Health
Katherine Marshall, USDA Centers for Epidemiology and Animal Health
Rachel McGuigan, USDA Centers for Epidemiology and Animal Health
Matthew Vuolo, USDA Centers for Epidemiology and Animal Health
Alexis Freifeld, USDA Centers for Epidemiology and Animal Health
Mia Kim Torchetti, USDA APHIS National Veterinary Services Laboratories
Kristina Lantz, USDA APHIS National Veterinary Services Laboratories
Amy H. Delgado, USDA Centers for Epidemiology and Animal Health

Date of this Version

1-1-2023

Citation

Green AL, Branan M, Fields VL, Patyk K, Kolar SK, Beam A, Marshall K, McGuigan R, Vuolo M, Freifeld A, Torchetti MK, Lantz K and Delgado AH (2023) Investigation of risk factors for introduction of highly pathogenic avian influenza H5N1 virus onto table egg farms in the United States, 2022: a case–control study. Front. Vet. Sci. 10:1229008. doi: 10.3389/fvets.2023.1229008

Comments

U.S. government work

Abstract

Introduction: The 2022–2023 highly pathogenic avian influenza (HPAI) H5N1 outbreak in the United States (U.S.) is the most geographically extensive and costly animal health event in U.S. history. In 2022 alone, over 57 million commercial and backyard poultry in 47 U.S. states were affected. Over 75% of affected poultry were part of the commercial table egg production sector. Methods: We conducted a case–control study to identify potential risk factors for introduction of HPAI virus onto commercial table egg operations. Univariate and multivariable analyses were conducted to compare farm characteristics, management, and biosecurity factors on case and control farms. Results: Factors associated with increased risk of infection included being in an existing control zone, sightings of wild waterfowl, mowing or bush hogging vegetation less than 4 times a month, having an off-site method of daily mortality disposal (off-site composting or burial, rendering, or landfill), and wild bird access to feed/feed ingredients at least some of the time. Protective factors included a high level of vehicle washing for trucks and trailers entering the farm (a composite variable that included having a permanent wash station), having designated personnel assigned to specific barns, having a farm entrance gate, and requiring a change of clothing for workers entering poultry barns. Discussion: Study results improve our understanding of risk factors for HPAI infection and control measures for preventing HPAI on commercial U.S. table egg farms.