Pathogenic And Phylogenetic Analysis Of Newcastle Disease Virus Isolated From Wild Birds In Qinling Mountains

Newcastle disease (ND) is a highly contagious disease commonly found in most avianspecies, and has caused serious economic losses of poultry industry throughout the world. NDis caused by Newcastle disease virus (NDV) which is classified as the Avulavirus in thefamily Paramyxoviridae. As a negative-sense, single stranded, non-segmented envelopedRNA virus, NDV genome is approximately15.2kb long, coding for six major proteins. Theenvelope contains two interactive surface glycoproteins, the hemagglutinin-neuraminidase(HN) and the fusion (F) proteins, which play a crucial role in virus infection and virulence.The HN protein is responsible for attachment to host cell-surface receptors, the F proteinmediate fusion of viral and cellular membranes and help the virus particle to penetrate in hostcell. Moreover, cleavage of the F protein is the primary determinant of virulence asdetermined by motifs from112to117.Wild birds are considered as natural reservoir hosts for NDV and at least241differentbird species can be naturally or experimentally infected with NDV and mostly harborlentogenic strains. NDV in wild birds were discovered can be much possible to be transferredback to domestic poultry and outbreaks of ND in domestic poutry. In addition, wild birdsmaybe provide a suitable environment for NDV to variation. Qinling mountain is one of theeleven global significance areas of the biodiversity protection, and also the migratory area formigrant birds in central China, possessing the huge birds resources. Thus, assessment of theepidemically status of NDV in Qinling mountain not only can help us to protect the birdresources in China more effectively, but also enable us to better understand molecularepidemiology of NDV, which can serve as the theoretical basis to help predict the prevalenceof ND effectively. The main results of this study as follow:1.252throat and cloacal swabs obtained from healthy wild birds used to isolate NDVwhich characterized by chicken embryo inoculation test, hemagglutination, hemagglutinationinhibition tests and RT-PCR. Five NDVs were isolated and identified from Great SpottedWoodpecker, Grey-faced Woodpecker, Azure-winged Magpie, Eurasian Blackbird, White-cheeked Starling,respectively. The result showed that the overall separation rate was2%. 2. The virulence of5isolates were evaluated by Mean death time (MDT),Intracerebralpathogenicity index (ICPI) and Intravenous pathogenicity index (IVPI), and the results were60～76.8h,0.9～1.261and0.41～0.81, belonging to moderate virus. In addition, the ICPIresults of5isolates at least more than0.9, having potential threat to poultry industry.3. Phylogenetic analysis of partial F gene (47～420bp) showed that5NDVs belong toVIb genotype, having the closest genetic relationship with pigeon NDV. Deduced amino acidsequences of the cleavage sites of fusion (F) protein revealed that all strains had the velogenicmolecular characteristics, sharing same motifs112RRQKRF1174. By comparison of the deduced amino acid sequences of hemagglutinin-neuraminidase(HN) glycoprotein, the similarity among the5isolates was99.5%～99.8%, shared97.4%～98%,91.1%～96.5%,87.1%～87.4%and89%～89.3%identities with genotype VIpigeon NDV,genotype VI chicken NDV,La Sota and F48E9,respectively.