Gene Sequence Analysis And Pathogenicity Study Of Three Strains Of Type 1 Duck Hepatitis A Virus

Changes in gene sequences of duck hepatitis A virus type 1(DHAV-1)were analyzed in order to understand the pathogenicity of the virus.Through virus isolation,RT-PCR identification,genome sequencing and phylogenetic tree analysis from duck farm disease in Shandong province in 2018,we isolated three strain of DHAV-1.Then,Animal regression tests were conducted to study the pathogenicity of three strains of virus and its ability to replicate in the organs of ducklings.Duck embryo allantoic solution from 24 hours to 96 hours of dead duck embryo was collected as rt-pcr sample by inoculation with sample of diseased material.All other duck-host viruses were PCR negative and only type 1 duck hepatitis virus was electrophoresis positive.By genome-wide sequencing and phylogenetic tree analysis,three viruses were named:SD37,SD63,SE5.By genome-wide sequencing and phylogenetic tree analysis,the homology of three isolated virus strains with reference strains isolated from 2011 to 2016 was 97.8%to 99.2%.Sequence homology of three virus VP1 genes ranged from 94.3%to 99.9%.Animal regression experiments,three strains of virus were challenged by nasal drip of method and the control group was added,the survival rate of SD37,SD63,SE5 was 0%,87.5%,100%.Through determination of organ virus titer by titration of duck embryo and real-time quantitative PCR,the content of organ virus from high to low is liver,spleen and kidney.The results of analysis of three strains isolated from Shandong region showed that there were antigenic differences among different strains,virulence differences,the most virulent of SD37,lentogen virulence of SD63 and SE5,and strong replication ability of virus in liver.