Identification Of Newcastle Disease Virus From Chicken And The Genome Molecular Characeristics Of HN09-68 And HN09-83 Strains

Newcastle disease virus (NDV) is one of the most important infectious agents in poultry, affecting a wide variety of birds and causing impoutant economic losses.The virus belongs to the family paramxoviridae , subfamily paramyxovirinae, in the genus Avulavirus, and encompasses a diverse group of single-stranded, negative-sense, nonsegmented RNA virues of approximately 15kb. The genome encodes six major proteins in the 3'to 5'direction: nucleoprotein(NP), phosphoprotein (P), matrix protein (M),fusion protein (F), haemagglutinin- neuraminidase (HN) and large polymerase protein (L).1 Isolation, Identified and The biological characteristics of Two NDV strains. After chicken embryos inoculation and serological identification, 17 NDV isolates were identified and collected from 64 ND suspected specimens. The isolation rate was about 26.6%. Two isolates were purified plaque-purification test, and characterized biologically. Based on its MDT(53h,59.5h) and ICPI(1.75,19.5),the isolates were predicted to be velogenic isolates. Statistics showed that ND occurred when the production of chicken was high, occurrence on Broiler was more than Layers. Moreover,it usually occurred on Chick. Hence, ND is still one of the dieases which hazard poultry industry. Different isolation strains had differences among regions.2 Genome and genetic characterization analyses of Two NDV strains.14 pairs of primers were designed to amplify the specific gene fragment by RT-PCR and sequenced. The complete genome sequence was analysised by SeqMan. The genomic sequence consists of 15192nt, which agree with the"rule of six", the two islotates , Homology between the two isolation was 98.6%. the leader sequence was 55 nt, and the trailer sequence was 114 nt in size. The additional six bases of two NDV strains lie in the noncoding region of the 3'terminus of the NP gene. The amino-acid sequence of the fusion protein cleavage site in two isolates was ,which is a typical sequence of velogenic strains and is in agreement with the results of in-vivo pathogenicity tests. A single amino acid change ,from glutamic acid (E) to lysine(K) at codon 347(E347K). The study showed that more non-sense mutation occurred in coding region and non-coding region of NDV protein gene. Homology between the two strains was high, however, homology between the two strains from abroad was low. Prevalence of NDV had the same tendency and had regional features.