The Isolation And Identification Of Newcastle Disease Virus In The Changchun Area And The Genetic Evolution Analysis Of F Gene

Newcastle disease (ND) has caused many worldwide pandemic since it was firstdescribed in1926, the disease continues to negatively impact poultry producers byinfecting birds worldwide. With the advances made in the diagnosis and vaccinationfor Newcastle disease since1970s and1980s, the occurrence of ND decreasedsignificantly. Meanwhile with the widely use of the ND vaccine, the occurrence ofND had some new changes, ND still happen in the chicken which were immunized orhad a very high ND antibody.Several reports showed that the reason for this situationmay be the ND compulsory immunization policy and the multiple or unreasonableimmunizations in China. So the study for the isolation, identification and sequenceanalysis of Newcastle disease virus in a certain area will contribute to theunderstanding of the occurrence, variation and development of ND local strains. Inaddition, through the immunology research, the protection efficiency in the region canbe measured, and can provide important reference for the control work in this area.NDV from Changchun area were studied in this paper. Epidemic materials werecollected from six regions in Changchun area such as Jingyue, Shuangyang, Dehuiand so on.10suspected ND epidemic materials (Jilin-CC-01, Jilin-CC-02,Jilin-CC-03, Jilin-SY-04, Jilin-DH-05, Jilin-DH-06, Jilin-JT-07, Jiln-JT-08,Jilin-NA-09, Jilin-YS-10) were inoculated in the10days old SPF chicken embryoallantoic cavity and all died within24~72h. The10separated allantoic liquid wereanalyzed by hemagglutination test (HA), hemagglutination inhibition test (HI) andRT-PCR, and the10positive NDV were identified successfully. By the threeindicators of toxicity test (MDT, ICPI, IVPI), the identified10local NDV are thestrong strains.Animal infection experiments were taken on the10local NDV stains, it wasfound that the10local NDV stains caused the animal morbidity and death, theincidence rate was from80%~100%and the mortality rate was from60%~100%. Theinfected chicken group appeared the symptom from2~3d, and died from3~6d. At thesame time,30blood serum samples were collected from each group, antibody titerwere relatively low, and has relatively high difference. Evolutionary trees were drawnaccording to F gene sequences of the10NDV, and compared with the10NDVisolated from Beijing(KF935230), Shandong(JN400897), Jilin(KC542899),Liaoning(KC542905), the results showed that Jilin-CC-01and KF935230has a closer genetic relationship, its homology was91.67%; Jilin-CC-02, Jilin-CC-03andKF935230were in the same branch, homology was92%and92.66%; Jilin-SY-04andJilin-DH-06was in the same branche, and the homology with JN400897was97.41%and98.17%; Jilin-DH-05and KC542899in the same branches, has a close geneticrelationship, the homology was99.59%; Jilin-JT-07and Jilin-JT-08were in the samebranch, and has a close genetic relationship with KC542905, and the homology was94.83%and94.29%; the homology of Jilin-NA-9, Jilin-YS-10and KC542905were96.71%,95.93%.Based on the close genetic relationship between Jilin-DH-05and KC542899(thehomology was99.59%). Jilin-DH-05was selected for vaccine research, ComparedJilin-DH-05inactivated vaccine with inactivated vaccine LaSota by ELISA, theresults showed that both humoral immunity levels increased continuously, and stillquite high in56days. The cell immune levels increased significantly before28d, andbegan to decrease from28d. Jilin-DH-05inactivated vaccine has the same immuneefficacy as the inactivated LaSota, so the local epidemic ND strain can be protectedcompletely by the existing vaccines.