| Duckviral hepatitis(DVH) is a highly lethal ducklings, viral infectious disease which spreads rapidly. Clinically, it is characterized by the neurological symptoms and liver enlargement, the surface bleeding. It mainly infects 6 weeks old ducklings, especially 2 to 3-week-old ducklings are most susceptible, adult ducks are resistant. It is different of the mortality, after the onset of different ages ducklings, some as high as 95%, and some less than 15%. The resisted duck became frozen duck, impeded growth and development. The disease is one of the most serious infectious disease harming the duck industry. Although the chicken embryos attenuated vaccine and inactivated vaccine of the duck hepatitis have been large scale extended in our country, in the actual production, it still outbreaks causing serious harm to the duck industry. And on the duck hepatitis prevention and treatment, at present, the farmers rely mainly on injected hyperimmune egg yolk. But the yolk antibody is variable quality, the effect is not guaranteed, because the yolk antibody production is not standard.In the experiment, a suspected duck hepatitis virus strain was isolated from clinical disease in a group of ducklings, and then it was identified by biological method and measured of virulence. Duck hepatitis virus type I identify primer pairs were used for nested RT-PCR amplification to extracted viral RNA. According to the measured virus ELD50, there was a neutralization test on the isolated strains and positive serum of duck hepatitis virus type I. After the attacking drug test on ducklings, the pathologic livers was made of ultrathin sections, and morphological characteristics of virus particles was observed. Susceptible ducklings were inoculated with the strain, and the dead ducks’livers were taken for the tissue inactivated vaccine, those had different vaccine adjuvant, three groups were setted with propolis group, astragalus group and a contrast group without adjuvant. According to the process of immune, high-yield laying hens were immuned, and the eggs were collected. It was groped for sure on the preparation conditions of three groups of yolk antibody, through the neutralization test on the three groups yolk antibody titers were tested, and the higher titer yolk antibody was selected to be applied to the treatment of clinical disease ducklings.The results showed that the virus particles,30nm round without enveloped, can be observed around the endoplasmic reticulum by the electron microscope. The strain’s ELD50 was 10-5.659/0.2 ml, and the isolated virus can be neutralized by the positive serum of duck hepatitis virus type I, the neutralizing is 1:79. The amplified stripe by nested RT-PCR was expectation, and it had homology lower rate with the four strains of Shandong strain by homology analysis. Three groups were collected for the neutralization test on the yolk antibody titers, astragalus group was 210.8, propolis group was 29, contrast group was 27.82,respectively, antibody titer of the contrast group was lower than the other two groups obviously.The optimum pH was 6.1 for the yolk antibody preparation, the optimum dilution was 1:10, yolk antibodies had relatively high protein conten in this conditiont. It was found that the astragalus group had the highest protein content of egg yolk antibodies in the three groups under optimal conditions, propolis group followed, the contrast group lowest. The astragalus yolk antibody, the higher antibody titers, was producted in quantity and applied on clinic. It was found that the cure rate of the hyperimmune egg yolk antibodies against type I duck viral is very high, which had a good protection on ducklings.In this study, it was based on the duck hepatitis cases in clinic, the experiment laid a solid foundation for efficient organization inactivated seedlings and yolk antibody development. provided some technical measures and theoretical basis on the effective prevention and control of duck viral hepatitis pop. |
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