| Since the epidemic of Newcastle disease (ND) is becoming more and more complicated in recent years, the immune fail always take place in chickens. In order to prevent and control the epidemic of ND better in Luoyang district, the study had been done on the flowing six respects.1. Identification of Newcastle disease virus isolates and their biological characteristicsRepresentative NDV strains collected during 1998~2002 in different parts of Luoyang area were isolated, identified and studied on their biological characteristics. The results showed that 15 NDV strains are hemagglutination (HA) active and hemagglutination inhibition (HI) active, and the pathogenicity to chicken embryo could be inhibited by ND positive serum. By means of the test of mean death time (MDT) of chicken embryo, intracerebral pathogenicity index (ICPI) of 1-day-old chicken and intravenous pathogenicity index (IVPI) in 6-week-old chicken, LD-6-01 and LR-2-00 strains were verified to be lentogenic strains, their hemagglutinin were stable to heat and belonged to slow type of hemagglutinating-free; the other strains were all virulent, their hemagglutinin were not stable to heat and belonged to fast type of hemagglutinating-free. 15 NDV strains were able to agglutinate chicken and human erythrocytes, however, their ability of agglutinating the erythrocytes of sheep, goat, swine, horse and cow were different. Challenged by 2 lentogenic NDV strains, the chickens with 61og2 HI antibody obtained 100% protection, the same chickens challenged by LG-1-99, LR-1-98, LD-4-01 and LD-3-00 strains obtained 70~90% protection, and the same chickens only obtained 0-20% protection after challenged by other 9 virulent strains. But the pathogenic and death time were postponed obviously in all the unprotected chickens.2. Investigation on the molecular epidemiology of Newcastle disease virus in Luoyang areaMain function fragment of Fusion gene of 15 NDV strains were amplified by reveres transcription- polymerase chain reaction (RT-PCR) and sequenced after being cloned into pMD-18-T plasmids. By means of sequence analysis, the phylogenetic tree was constructed based on the obtained nucleotide (from 47 to 435 bp), and the virulence and genotype of 15 NDV strains were confirmed. The results showed that the 15 isolates can be divided obviously into three groups. The nucleotide sequenceand deduced amino acid sequences of this fragment of 15 NDV strains were compared with that of published NDV F genes respectively. Their homology was higher in the same group and lower between the groups, no difference caused by breed was found in this test. There were 9 strains in the first group, 4 strains in the second group and 2 strains in the third group. The NDV strains in group 1, 2, 3 belonged to genotype VII VI and II respectively. It revealed that the ND epidemic in Luoyang area were caused mainly by new genotype VD strains, moreover, the traditional genotype VI and II strains were also responsible for the ND prevalence .3. Preparation of trivalent oil-adjuvant inactivated vaccine against Newcastle disease virusTrivalent oil-adjuvant inactivated vaccine was prepared successfully with two isolated strains of genotype VI and W (LD-3-00 and LD-7-02) and La Sota strain of Newcastle disease virus. The effects were detected under experimental and field conditions. The results showed that the vaccine was safe and effective, the average titer of hemagglutination inhibition (HI) antibody remained 7.51og2 at 42 days post-inoculation and the immunization protective rate was 100%. It indicated that the vaccine can effectively prevent and control Newcastle disease resulted from various genotypes NDV strain.4. Efficacy comparison of trivalent oil-adjuvant inactivated vaccine with inactivated La Sota vaccine against Newcastle disease virus.The immune efficacy were compared between trivalent oil adjuvant inactivated vaccine and inactivated La Sota vaccine. The results showed that there is no apparent difference of HI antibody between chickens inoc... |
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