Virulent newcastle disease viruses from chicken origin are more pathogenic and transmissible than viruses normally maintained in wild birds

Authors: FERREIRA, HELENA - Orise Fellow; Taylor, Tonya; SABRA, MAHMOUD - South Valley University; DIMITROV, KIRIL - Consultant; Afonso, Claudio; Suarez, David

Submitted to: Veterinary Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/3/2019
Publication Date: 7/25/2019
Publication URL: https://handle.nal.usda.gov/10113/6461958
Citation: Ferreira, H.L., Taylor, T.L., Sabra, M., Dimitrov, K.M., Afonso, C.L., Suarez, D.L. 2019. Virulent newcastle disease viruses from chicken origin are more pathogenic and transmissible than viruses normally maintained in wild birds. Veterinary Microbiology. 235:25-34. https://doi.org/10.1016/j.vetmic.2019.06.004.
DOI: https://doi.org/10.1016/j.vetmic.2019.06.004

Interpretive Summary: Newcastle disease viruses (NDV) continue to be an ongoing threat to the poultry industry and are reportable to the World Organization for Animal Health (OIE). These viruses are known to infect over 250 avian species, and they are often identified in wild birds, which are speculated to play a role in the spread of the virus. NDV are commonly found and cause disease in two wild bird populations (pigeons and cormorants) in countries that are free of NDV in poultry. Therefore, the potential transmission of NDV from wild pigeons and cormorants continues to be a concern for poultry producers. The main objective of this study was to determine if the chicken and wild bird viruses could cause demonstrable differences to infect chickens and to be transmitted to contact chickens. The present study could see a clear difference among viruses isolated from chicken, cormorant, and pigeon samples. Not surprisingly, the chicken-origin viruses were able to infect chickens and efficiently transmit the virus to contact controls using a low, medium, and a high dose of virus. Conversely, the cormorant virus was pathogenic to chickens using a high and a medium dose but not with a low dose. Surprisingly, even when using a high infectious dose, transmission of both wild bird viruses from inoculated to contact chickens still did not occur. As for the pigeon virus, even at the high virus dose, no clinical signs in directly-infected chickens nor transmission to contact chickens were observed. Our results may explain why pigeon and cormorant lineage viruses are rarely found in poultry.

Technical Abstract: Five, class II, virulent Newcastle disease virus (vNDV) isolates of different genotypes from different host species were evaluated for their ability to infect, cause disease, and transmit to naïve chickens. Groups of five birds received a low, medium, or high dose, by the oculonasal route, of one of the following vNDV: three chicken-origin, one cormorant-origin, and one pigeon-origin. Three naïve birds were added to each group at two days post-inoculation (DPI) to evaluate transmission. Virus shedding was quantified from swabs (2/4/7 DPI), and seroconversion was evaluated at 14 DPI. All inoculated and contact birds in the chicken-origin vNDV groups succumbed to infection, displaying clinical signs typical of Newcastle disease and shed virus titers above 6 log10 EID50/ml. Birds receiving a high and medium dose of the cormorant virus showed primarily neurological clinical signs with 80% and 60% mortality, respectively. The chickens showing clinical disease shed virus at titers below 4 log10 EID50/ml, and the remaining bird in the high dose group seroconverted with a high HI titer. For the pigeon-origin virus, no clinical signs were observed in any of the birds, but all 5 chickens in the high challenge dose and one bird in the medium challenge group shed virus at mean titers of 3.1 and 2.2 log10 EID50/ml, respectively. Overall, the chicken-origin viruses infected chickens and efficiently transmitted to naïve birds, while the cormorant- and pigeon-origin viruses infected chickens only at the higher doses and did not transmit to other birds.