RESUMO
Twenty Newcastle disease virus (NDV) strains were isolated from chickens and geese in the field outbreaks during 2005 and 2006 in some regions of Jiangsu and Guangxi province. Assessment of the virulence by MDT and ICPI, RT-PCR and sequence analysis of fusion protein gene were used to compare the properties of NDV isolates. The results indicated that MDT and ICPI of the isolates were 45.3h - 58.2h and 1.61 - 2.00 respectively, which confirmed that the all NDV isolates were highly virulent. And their hemagglutinin were not resistant to heat and belonged to fast pattern of elution. The results of nucleotide sequencing and phylogentic analysis of fusion protein gene showed that the twenty strains shared homology from 79.7% to 100% among themselves, from 78.1% to 83.4% and from 80.2% to 90.1% with NDV LaSota, F48E8, respectively. The putative amino acid sequences of fusion protein at the cleavage sites of all the isolates were 112R-R-Q-R/K-R-F117, with the motif characteristics of the virulent NDV strain, which was in accordant with the results of assessment of the pathogenicity. The phylogentic tree based on sequences of fusion protein gene variable regions (47-420nt) revealed that the 18 strains belonged to sub-genotype VIId and the others belonged to an old genotype III of NDV, revealing that subgenotype VIId virus was responsible for the NDV outbreaks in some regions of Jiangsu and Guangxi promince recently.