Phylogeny, pathogenicity and transmissibility of a genotype XII Newcastle disease virus in chicken and goose.

Although Newcastle disease virus (NDV) has a worldwide distribution, some NDV genotypes have more regional geographical ranges within continents. In this study, we isolated a subgenotype XIIb NDV strain, Goose/CH/GD/E115/2017 (E115), from geese in Guangdong province, Southern China, in 2017. Phylogenetic analysis showed that E115 and six other NDVs from geese in China were grouped under subgenotype XIIb and were distinct from subgenotype XIIa, isolated from chickens in South Africa, and subgenotype XIId, isolated from chickens in Vietnam. To better understand the pathogenicity and transmission of the subgenotype XIIb NDVs from geese in Guangdong province, we inoculated chickens and geese with 106 EID50 of the E115 virus. Eight hours after inoculation, three naïve chickens and three naïve geese were co-housed with the infected chickens or geese to assess intraspecific and interspecific horizontal transmission of the E115 virus. The E115 virus induced significant clinical signs without mortality in chickens, while it was not pathogenic to geese. Intraspecific and interspecific horizontal transmission of the E115 virus was observed among chickens and geese via direct contact. Furthermore, although the current vaccines provided complete protection against disease in chickens after challenging them with the E115 virus, the virus could also be transmitted from vaccinated chickens to naïve contact chickens. Collectively, our findings highlight the need for avoiding the mixing of different bird species to reduce cross-species transmission and for surveillance of NDV in waterfowl.