|AYALA, ANDREA - University Of Georgia|
|HERNANDEZ, SONIA - University Of Georgia|
|WELCH, CATHARINE - University Of Georgia|
|DIMITROV, KIRIL - Consultant|
|GORAICHUK, IRYNA - Consultant|
Submitted to: Avian Diseases
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/20/2019
Publication Date: 9/15/2019
Publication URL: https://handle.nal.usda.gov/10113/6743214
Citation: Ayala, A.J., Hernandez, S.M., Olivier, T.L., Welch, C.N., Dimitrov, K., Goraichuk, I.V., Afonso, C.L., Miller, P.J. 2019. Experimental infection and transmission of Newcastle disease vaccine virus in four wild passerines. Avian Diseases. 63(3):389-399. https://doi.org/10.1637/11980-092918-Reg.1.
Interpretive Summary: Newcastle disease outbreaks are a global challenge to the poultry industry, as effective management of this disease depend on understanding of the ecology and transmission properties of the virus. Although the susceptibility of wild birds to NDV has been largely accepted, their role in the short-term spread of the virus, as maintenance hosts, remain unclear. Biosecurity in the backyard poultry sector is limited and the attraction of ‘feeder birds,’ i.e. passerines and near-passerines, to chicken feed is a new potential link for NDV transmission. In urban and suburban areas of the U.S, the continued rise in the ownership of backyard flocks and lack of oversight concerning vaccination and biosecurity protocols have the potential to leave agriculturally associated passerines and the commercial poultry industry vulnerable to future NDV outbreaks. Prior work has already demonstrated that wild-type NDV and vaccine strains of poultry origin can spill back into wild birds; however, these studies have been largely cross-sectional and unable to assess the susceptibility of passerines to transmission. House Finches American Goldfinches, Northern Cardinals, and Brown-headed are native songbirds that often share habitat with backyard chickens . In this study, we conducted three experimental inoculation treatments using groups of these species by directly exposing them to the lentogenic live Newcastle disease LaSota vaccine or otherwise exposed vaccinated chickens. We measured each species viral shedding, duration, and antibody response over a two-week period.
Technical Abstract: Our prior work has shown that live poultry vaccines have been intermittently isolated from wild birds sampled during field surveillance studies for Newcastle disease virus (NDV). Thus, we experimentally investigated the susceptibility of four native agriculturally associated wild bird species to the NDV LaSota vaccine and evaluated the shedding dynamics, potential transmission from chickens, and humoral antibody responses. To test susceptibility, we inoculated wild-caught, immunologically NDV-naïve house finches (Haemorhous mexicanus; n = 16), brown-headed cowbirds (Molothrus ater; n = 9), northern cardinals (Cardinalis cardinalis; n = 6), and American goldfinches (Spinus tristis; n = 12) with 0.1 ml (106.7 mean embryo infectious doses [EID50/ml]) of NDV LaSota vaccine via the oculo-nasal route. To test transmission between chickens and wild birds, adult specific-pathogen-free white leghorn chickens were inoculated similarly and cohoused in separate isolators with two to five wild birds of the species listed above. This design resulted in three treatments: wild bird direct inoculation (five groups) and wild bird exposure to one (two groups) or two inoculated chickens (six groups), respectively. Blood and oropharyngeal and cloacal swabs were collected before and after infection with the live vaccine. All wild birds that were directly inoculated with the LaSota vaccine shed virus as demonstrated by virus isolation (VI). Cardinals were the most susceptible species based on shedding viruses from 1 to 11 days postinoculation (dpi) with titers up to 104.9 EID50/ml. Although LaSota viruses were shed by all inoculated chickens and were present in the drinking water, most noninoculated wild birds cohoused with these chickens remained uninfected for 14 days as evidenced by VI. However, one American goldfinch tested positive for vaccine transmission by VI at 7 dpi and one house finch tested positive for vaccine transmission by real-time reverse-transcription PCR at 13 dpi. Only one directly inoculated cowbird (out of three) and two cardinals (out of two) developed NDV-specific hemagglutination inhibition antibody titers of 16, 16, and 128, respectively. No clinical signs were detected in the chickens or the wild birds postinoculation.