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Abstract
Newcastle disease virus (NDV), also known as avian orthoavulavirus-1, is among the most significant of poultry pathogens worldwide. In the United States, free-roaming backyard chickens are rarely subjected to biosecurity and bioexclusion methods that reduce the transmission of pathogens such as NDV among wild birds. Resources such as chicken feed, water, and coops attract passerines, increasing the likelihood of transmission between them two groups. Both in the field and under biosafety laboratory -2 (BSL-2) conditions, we assessed passerine susceptibility, transmission capabilities, and behaviors conducive to infection with lentogenic (low-virulent) NDV from backyard chickens. In BSL-2, Northern Cardinals (Cardinalis cardinalis), Brown-headed Cowbirds (Molothrus ater), American Goldfinches (Spinus tristis) and House Finches (Haemorhous mexicanus) shed virus when directly inoculated with the LaSota vaccine virus, although antibody responses and shedding patterns varied. The same species were co-housed for 14 days with specific-pathogen free (SPF) chickens inoculated with LaSota. While Northern Cardinals and Brown-headed Cowbirds remained uninfected, 20% of House Finches (1/4) and (1/5) American Goldfinches tested positive by real-time PCR and virus isolation. In North Georgia, we collected 1,574 observations of 72 species across three sites associated with backyard chickens. One site was managed as a free-ranging flock, one site primarily cooped their chickens, and the third site served as the control, without chickens. Fourteen species were repeatedly observed performing behaviors that were conducive to NDV transmission, the consumption of chicken feed. Chipping Sparrows (Spizella passerina), Northern Cardinals, and Tufted Titmice (Baeolophus bicolor) accounted for the greatest number of visits. To understand the spillover dynamics of lentogenic NDV from backyard chickens to wild birds, we inoculated both backyard chicken flocks with the LaSota vaccine virus and surveyed the third site as the control. At the two inoculated sites, thirteen species of passerines either developed or demonstrated increases in NDV antibody titers, whereas all wild birds at the control site remained uninfected. Antibody titers did not vary across wild birds at each site associated with chickens. Our work demonstrates that interactions between wild birds and chickens frequently occur, and that we must educate backyard chicken owners on how to mitigate disease risks such as NDV to native birds.