Surveillance and molecular characterization of Newcastle disease virus in seafowl from coastal areas of China in 2011.

Four Newcastle disease virus (NDV) isolates were obtained from 997 fecal and tissue samples were collected in 2011 from seafowl that included seagull, sea duck, and swan from the coastal areas of Guangdong, Jiangsu, and Shandong in China. These isolates (SD1, SD2, GD1, and JS1) were characterized for their pathogenicity according to their mean death time, intracerebral pathogenicity index and intravenous pathogenicity index. Full-length fusion protein genes containing the cleavage site were sequenced, and amino-acid sequences around the cleavage site were deduced. One isolate (SD2) was virulent to poultry as indicated by its mean death time, intracerebral pathogenicity index, and fusion gene cleavage site sequence, which was specific for virulent NDV ((112)R-R-Q-K-R-F(117)). The phylogenic analysis indicated that three of the isolates (SD1, GD1, and JS1) belonged to genotype II and the virulent isolate (SD2) belonged to genotype VIId. These findings suggest that some seafowl NDVs in the coastal areas of China have different virulences and molecular characterizations, and these NDVs have some similarity with vaccine- or poultry-adapted isolates.