Genetic analysis of avian paramyxovirus-1 (Newcastle disease virus) isolates obtained from swine populations in China related to commonly utilized commercial vaccine strains.

Newcastle disease virus (NDV) has been thought to only infect avian species. However, at least eight NDV strains were isolated from swine populations in China during 1999-2006, four of which were characterized genetically and phylogenetically. Genetic analysis revealed that JL106 and SP13 had a (112)G-R-Q-G-R-L(117) motif at the cleavage site of F protein, while JL01 and MP01 possessed a (112)G-K-Q-G-R-L(117) motif, which indicated that all of them were typical of low-virulence viruses. Phylogenetic analysis based on the full-length F gene sequences showed that JL106 and SP13 belonged to genotype II, similar to the commonly utilized commercial La Sota vaccine strain in China. While JL01 and MP01 clustered within genotype I, genetically identical to the V4 vaccine strain. The animal trials showed that JL106 can effectively infect chickens. The present results indicated that the use of live La Sota and V4 vaccines and close contact between avian and pigs maybe resulted in cross-species infection, therefore, it is necessary to further carry out swine NDV epidemiology surveillance.