Genetic Characterization and Evolutionary Analysis of Emerging Newcastle Disease Virus Isolated from Tibetan Chickens

Newcastle disease (ND) is one of the highly contagious disease responsible for devastating outbreaks and considerable economic losses to poultry industry in China. However, no information is available about NDV in Tibet region; the aim of this study was to determine the genetic characterization and evolutionary analysis of NDV in Tibetan chickens. Four NDVs were isolated from an outbreak in Tibetan chickens. The pathogenicity of the isolates was determined by mean death time (MDT), intracerebral pathogenicity index (ICPI) and amino acid sequencing (112 to 117) of F protein. While the genetic characterization of F gene was determined by sequencing the isolated NDVs and phylogenetic relationship was established with the help of reference strains. Pathogenicity experiments revealed that XZ-F10 and XZ-F20 strains were lentogenic pathotype, while the remaining XZ-F2-1 and XZ-F4-6 strains were velogenic pathotype. The deduced amino acid sequences of the cleavage site of the F protein confirmed our results. Phylogenic analysis of these strains indicated that both XZ-F2-1 and XZ-F4-6 belong to genotype VII. However, XZ-F10 and XZ-F20 strains were assigned to genotypes II. The present study highlights the need for continuous surveillance of NDV in Tibetan chickens; moreover, this study will provide a reference for the local government to make the strategies and control emerging NDV in Tibet.