Isolation And Identification Of NDV And Genetic Evolution Analysis Of NDV F Gene

Newcastle disease is one of the most serious infectious diseases caused by Newcastle disease virus (NDV) in poultry. It causes high morbidity and mortality in non-immunized chickens even in some immunized chickens population with respiratory tract infection as well as egg drop.In this study, the virus strains was isolated from layer and chicken suspected with Newcastle disease(ND). And then, the Newcastle disease virus(NDV) was identified and purified. The RT-PCR was used to clone F genes of the NDV isolated. And the genetic evolution analysis of F gene was done. This study consists of three parts:1. Isolation and identification of NDVTwo NDV field isolates were isolated from the layer and chicken in Shandong province. The viruses were identified by HI test and animal regression experiment.2. Plaque-purification and virulence test of NDVThe plaque-purification was used to purify NDV. And the MDT, ICPI and IVPI were detected respectively. The results suggested that the two NDV strains isolated were all designated as velogenic isolates. The pathogenicity tests were repeated twice and the results were identical before and after plaque purification.3. Genetic evolution analysis of NDV F geneF gene,predicted fragment size 1700bp,was amplified by RT-PCR from the two NDV strains. RT-PCR amplified fragment coincided with the expected size and sequences result of DNA demonstrated that the sequences were exactly correct.Genetic evolution,combined with related information of Shandong strains in recent years ,were conducted to analysis the variation condition of F gene. The results showed that the cleavage motif of F protein from the two strains was ¹¹²R-R-Q-K-R-F¹¹⁷ which was the characteristic of velogenic strain. Nucleotide analysis revealed that the isolated was of the genotypeâ…¦.