Isolation And Identification And Study On Pathogenicity Of One Strain High Virulent Newcastle Disease Virus

Newcastle disease is an acute septic infectious disease that caused by Newcastledisease virus. The disease is mainly characterized by diarrhea, neurological symptoms, focalglandular gastric bleeding or ulcers, intestinal mucosal bleeding and necrosis of the pancreasor the spleen. This disease has high morbidity and mortality and has serious harm to thechiken industry.This study contains two parts:Part1: Establishment of RT-PCR diagnostic method for Newcastle diseaseThe fusion (F) gene fragment (550bp) of Newcastle disease was amplified by RT-PCRdiagnostic method using a pair of primers, which was designed according to F gene sequenceof chicken Newcastle disease virus, followed by specificity test and sensitivity test. Thespecificity test showed that the method could specially amplify the550bp gene-specificfragment of SD strain, while the amplification results of Infections bursal disease virus,H9N2subtype avian influenza virus, Marek’s disease virus were negative. Sensitivity testshowed that the minimum detectable amount of cDNA concentration was3pg/μL. Theestablished RT-PCR diagnostic method appeared to be fast, accurate, highly sensitive andspecific for the purpose.Part2: Study on Pathogenicity of Newcastle Disease ViruA strain virus isolated from the ill chicken in Shandong province was identified as Newcastle disease virus by HA, HI and neutralization of virus. The virus was named SD strain.The MDT, ICPI and IVPI for SD strain were47.4h,1.975and2.85, respectively. ELD50ofchicken embryos is10-9.6. Amino acid sequence analyzing showed that the isolate was genetype Ⅶ. The FPCS of SD strain between positions112and119were112-RRQKRF-117. Theresults indicated that SD isolate was virulent strain. The nucleotide homology of F gene is93.5%-98.3%between SD strain and those of gene type Ⅶ viruses isolated from chicken.And the nucleotide homology of F gene is95.2%-96.5%between SD strain and those of NDviruses isolated from ducks and gooses. The nucleotide homologies of F gene are respectively 85.8%and83.3%between SD strain and F48E9and Lasota strain. And the amino acidhomologies of F gene are respectively91.3%and88.4%between SD strain and F48E9andLasota strain.