Analysis Of The Complete Genome Sequence And Studies On The Virulence Of The QZ1401 Strain Of DHAV-3

Duck hepatitis virus(Duck hepatitis A virus, DHAV) and duck astrovirus(Duck astrovirus), caused by duck hepatitis virus(DHV), is characterized by a rapid spread of highly contagious and fatal disease in ducklings. The disease mainly infects duckings which age is from one week to three weeks. Which DHAV type of duck hepatitis were distributed worldwide, bring great losses to the duck industry. In this research, the complete genome sequence and the virulence of QZ1401 strain DHAV-3, which has been separated from the Shandong area, were tested. This research mainly includes the following two aspects:1. Sequence and analysis of the whole genome of DHAV-3 QZ1401 strainThe genome sequence of DHAV-3QZ1401 strain was amplified by RT-PCR, using primers which were designed according to the conserved region of DHAV-3 genome, sequencing and splicing. By performing a serious of analyzes of complete genome sequence, sequence analysis showed that the genomic structure of DHAV-3 QZ1401 strain is 5’UTR-L-VP0-VP3-VP1-2A1-2A2-2B-2C-3A-3B-3C-3D-3’UTR. QZ1401 Gene Bank strain and other logged DHAV-3 in the presence of highly homologous strains, the whole genomic nucleotide homology of 92.7% to 99.4% homology to the amino acid sequence of the coding region of the 96.5%-99.7 %, of the same serotype; phylogenetic analysis showed that 22 DHAV-3 can be divided into two genotypes: GⅠtype and G type. All field strains isolated in China(except China vaccine strain ⅡB63) belong G type; Korea isolated wild strain(including highly pathogenic strains Ⅰand low virulence strains), wild strains isolated in Vietnam and China vaccine strain B63 belong to genotype(G type). Its genotypⅡ Ⅱ e showed significant geographical features, and the virus strains isolated time no significant correlation.2. Study on the virulence of DHAV-3 QZ1401 strainIn this study, the fifth generation of blind spread viruses were inoculated allantoic fluid cavity through urine and intramuscular inoculation method to duck embryos and ducklings, statistics which the number of deaths within the specified time calculated by the Reed-Muench method duck ELD50 and ducklings LD50 embryos, to determine the virulence of DHAV-3 strain QZ1401. The result showed that: the strain after vaccination duck embryo and ducklings, can contribute to death and showed a typical duck hepatitis symptoms. Among them, the ELD50 of QZ1401 strain was 5-3.75/0.2m L and LD50 was 2-5.18/0.5m L.