Infectious Diseases 2019

Infectious Diseases 2019

Pathogenicity & transmission of vNDV from the 2018-19 California outbreak

Virology 531 (2019) 203-218 1 April, 2019

Newcastle Disease viruses that are virulent for chickens and cause ND are not commonly isolated in the U.S. 
In May of 2018, virulent Newcastle disease virus was detected in sick, backyard, exhibition chickens in southern California. Since, 401 backyard flocks (primarily chicken, two turkey, two mixed species, and one pigeon flocks), 4 commercial laying hens farms, one live bird market, and 2 feeder stores have been confirmed positive for vNDV in California, and one backyard flock in Utah. The pathogenesis and transmission potential of this virus (CA18), along with two genetically related and widely studied viruses, chicken/California/2002 and chicken/Belize/2008, were evaluated in both 3-week- and 62-week-old chickens given a low, medium, or high challenge dose (102, 104, 106EID50), oculo-nasal infection. All three viruses were highly virulent causing clinical signs, killing all the chickens in the medium and high dose groups, and efficiently transmitting to contacts. The three viruses also replicated in the reproductive tract of the adult hens. Virus shedding for all viruses was detected 24 hours after challenge, peaking with high titers at day 4 post challenge. Significant difference in viral shedding through the cloacal route between the young and adult birds was determined only in the groups inoculated with the CA18 high dose at 2 and 3 DPI.
The phylogenetic classification of the viruses studied here: genotype Vb of class II.
The CA18 virus presented an ICPI value of 1.76.