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

Helena L. Ferreira, Tonya L. Taylor, Kiril M. Dimitrov, Mahmoud Sabra, Claudio L. Afonso, David L. Suarez
Veterinary microbiology 2019 v.235 pp. 25-34
chickens, Newcastle disease, hosts, Avian orthoavulavirus 1, viruses, genotype, seroconversion, viral load, viral shedding, wild birds, virulence, mortality, signs and symptoms (animals and humans)
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.