| Duck viral hepatitis is caused by duck hepatitis virus a duck acute and highly fatal infectious disease, clinical mainly manifested as loss of appetite, neurological symptoms, sudden death and enlargement of the liver hemorrhage. Duck hepatitis virus type I belong to small RNA virus families, spherical or quasi spherical shape and diameter in the 20-40 NM, no envelope, no hemagglutination, duck, chicken, goose embryo allantoic cavity proliferation. Strong resistance to the virus, in the natural environment can survive long time, mainly Infected Ducklings within 3 weeks of age, after the onset of ducklings, sharp increases in mortality. The dead duck was opisthotonos phenomenon, necropsy liver characteristic symptoms hemorrhagic lesion is serious harm to support one of the duck plague. Although our country currently existing DHV vaccine production and widely used, but the disease still in the popular all over the country and caused significant loss of duck farming. Therefore, it is still an urgent problem to find a safe and effective vaccine strain, and develop an efficient duck viral hepatitis vaccine for prevention and control of duck hepatitis disease. Because the variation mechanism of duck hepatitis virus remains unclear, and 3C proteins as a function of proteins involved in lytic function, whether and variation of virulence related is not yet understood. In order to understand the duck hepatitis virus type 1(DHAV-1) gene variation, this study selected in SPF chicken embryos of viruses were passaged test by of 3C gene cloning, sequencing and virulence determination, provide the basis for the genetic variation of in-depth understanding of DHAV-1.In order to understand one type duck hepatitis virus(DHAV-1) in duck embryo passaged variation, in order to solution DHAV-1 virus particles in long-term recurrent infection, propagation and struggle with the host process. What happened and able to retain the advantages of genetic variation, this study will be completed the following two parts: In the first part:5 strains of DHAV-1 virus were cultured on SPF chicken embryos. 5 strains of DHAV-1 were ALY0901(1A), AZC14117(2A), A- disease virus(3A), A2-14(4A),(), ADNA-launch(5A),(), and(). Will the 5 strains of the virus in SPF chicken embryo culture experiment, spread to 60 generations, research found, chick embryo passage 5 generations ago, between 24 96 h chick embryo and no death, somatic embryos nor obvious lesions; 5 generation after 20 generations so far, chick embryo to the emergence of the phenomenon of death and somatic embryos obviously large amount of bleeding. Death time is concentrated in 72 h. There was no death in the 20-50 generation of 72 h, and the death of 50-60 in the chick embryo. The second part: the sequencing and sequence analysis of the 3C gene of DHAV-1 strain of chicken embryo Complete the ALY0901(1A), AZC14117(2A), a disease material poison(3A), A2-14(4A), ADNA-launch(5A) of five strains of poison every five generations of 3C gene cloning and sequencing, for obtained the nucleotide and amino acid sequence comparison, find out rule of variation in the gene, the study found that the base mutation, position is basically the same, but it is not amino acid mutations, suggesting that the virulence of the virus changes and 3C interval. |
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