| Duck viral hepatitis is an acute and highly contagious infectious disease caused by hepatitis a duck hepatitis virus,resulting huge economic losses to our country and even the world breeding.The virus is classified into three serotypes,type I,typeⅡand type Ⅲ.In2008,based on VP1,VP0,VP3 gene sequences and partial sequences of 3D gene,DHV-,I,A,B and C were three genotypes,respectively,corresponding to serotype I,Taiwan new and South korea..The small RNA virus group recommends the addition of the avian hepatitis virus,the duck hepatitis A virus,in the small RNA family of viruses,and belongs to the 3genotypes of serotype DHV-I.This paper will use the classification after 2008,will cause the duck hepatitis A virus belonging to the small RNA virus of avian hepatitis virus duck hepatitis A virus,called duck hepatitis A virus(DHAV),duck hepatitis A virus has been divided into three genotypes: A,B,C three a gene type.According to the gene sequence of the,one primer pair based on traditional DHAV-was designed to amplify the 699 bp fragment,and the results showed that the traditional DHAV-Ⅰexisted.Finally,the eight strains were isolated and purified by the method of duck embryo end-point.In order to obtain the whole genome,nine pairs of specific primers were designed,and then the target genes were sequenced.The whole genome sequence of the eight strains was obtained by using Seqman in DNASTRA.The genetic evolution analysis showed that the homology between the eight strains and the traditional DHAV was 93.1%-99.6%,and the homology between the Taiwan strain and the variant strain of Korea was 71.4%-72.2%.The results showed that all the eight isolates were DHAVA.Further study was the pathogenicity of six isolates on ducklingsBased on the genetic evolution analysis,the six strains were selected to infect ducklings by intranasal.After 3 dpi,three ducklings were killed in each group,and the heart,liver andspleen,lung,kidney,intestine,pancreas,and brain were collected to determine virus titration and distribution.The results revealed that the virus was detected in all of the organs and the DHAV load was significantly higher in the liver than in the other organs and the virus titration in the immune organs was relatively high,which showed that the distribution of DHAV in vivo from high to low was liver,spleen,bursa of Fabricius,intestine and heart.The results showed that the pathogenicity of the isolates was also different.The results of virus titration of DHAV-15-2,DHAV-4 and DHAV-40 in experimental group were significantly higher than those in the other three groups.In addition to,the DHAV-A was not pathogenic to mice and had no effect on body weight.On the whole our study focused on the sequences full-length genome of the eight DHAV-I isolates,and has verified the different isolates have different pathogenicity to ducklings. |
