Objective The pathogen that caused the high mortality disease showing symptoms of anterior arch reflexion and liver enlargement with dense bleeding points on ducklings at a duck farm in Fujian was identified. Specifically detectable polyclonal antibody was prepared for epidemiological study on the disease.
Method Liver tissues of the affected and died ducklings were collected for virus identification. Sequence of the virus was determined, and the pGEX-4T-1 vector used to construct a high-efficiency expression system for the dominant epitope gene. A VP1 polyclonal antibody was prepared, and specificity confirmed by western-blotting.
Result A virus was isolated from the liver of a duck suspected of viral hepatitis using non-immune duck embryos. The mortality rate by the isolated virus on the embryos after 6 generations of continuous transmission was approximately 70%. But the allantoic fluid of the dead embryo did not show hemagglutination in the blood of duck, chicken, mouse, or rabbit. In contrast, the mortality rate on 1-day-old ducklings injected with the allantoic fluid was 100%. The RT-PCR amplification and the entire genome sequence indicated the isolated virus to be positive for duck viral hepatitis virus 1. Furthermore, the gene homology between the virus and DQ226541.1 was 99.4%, and the sequence of VP1 amino acids consistent with that of DQ226541.1. The virus was code named Fujian 2015. Subsequently, the recombinant plasmid pGEX-4T-1-VP1 was successfully constructed, and the VP1 polyclonal antibody serum capable of specifically detecting VP1 protein prepared.
Conclusion A duck hepatitis virus type I was successfully isolated, and a VP1 polyclonal antibody of this strain prepared. Further study for the detection of duck hepatitis virus type I is in order.
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