Phylogenetic characterization and virulence of two Newcastle disease viruses isolated from wild birds in China.

Wild birds are considered as a natural reservoir of Newcastle disease virus (NDV). However, there is no information about genotype IX NDV from wild birds, especially from Columbiformes. In this study, two genotype IX NDV viruses were isolated from wild birds. One was from Eurasian Blackbird, while the other was from Spotted-necked dove. After purification by plaque technique, complete genomes of both viruses were sequenced. Phylogenetic analysis of partial fusion (F) gene and complete genome indicated both strains belonged to genotype IX. Based on intracerebral pathogenicity index (ICPI), the virus from Eurasian Blackbird was velogenic virus, while the strain from Spotted-necked dove was lentogenic virus. However, both strains showed one of velogenic cleavage sites. In addition, the strain from Eurasian Blackbird showed greater replication ability and generated larger fusion foci in vitro than that of strain from Spotted-necked dove. Comparing all the corresponding protein sequences of both strains, there were only 9 different amino acid residues between them. Furthermore, after analysis of these differences, the information about lentogenic NDV with multi-basic cleavage site was presented.