Isolation, Indentification And Study Of Biological Characterization Of Duck Hepatitis Virus In Hubei Province Of China

Duck viral hepatitis(DVH) is a fatal and rapidly spreading disease of young ducklings. The major pathologic change in infected ducklings is hepatitis.Three different viruses, duck hepatitis virus types 1,2 and 3,have been found to be associated with these symptoms.Duck virus hepatitis type 1was popular with in China.DHV was the biggest trouble maker of the development of the poultry industry.The present study describes isolating and identifying duck hepatitis of Hubei strain,the specific gene cloned and sequenced,neutralization test,and recurrence test,and protection test.A virulent field strains of DHV-1 were identified and their pathogenicity to both duck embryo and duckling were tested.The pathogeny of DHV was analysed through observation electron microscope and pathological change of duckling's internal organ,its bionomics.The study provided information for the epidemiology and taxology of DVH,and was useful for providing technological means and academic basis to effectively prevent.Gained some results as follow:Isolation two virus were obtained through uscovy duck embryo allantoic sacinoculation from duckling liver samples collected from Hubei provinces in China.The ELD₅₀ of the two virus strains detected with duck embryos were 10^-388/0.2mL and 10^-459/0.2mL respectively.Two virus were identified DVH type 1 and named JX strain, DYstrain.DHV-1 of conservation region fragments obtained in RT-PCR were sequenced and aligned 92-97%similarity at the nucleotide level with that of other DHV-1 strains listed in GenBank.Phylogenetic tree revealed that JX strains and DY strain was grouped into different lineage.The lethal rate of these isolates was 100 percent when inoculating 11-day-old duck embryos,and the mortality rate was 50 and 70 percent respectively When inoculating 4-day-old ducklings intramuscularly with these isolates.Dead ducklings showed the sign of opisthotonos,with swollen and punctuate hemorrhage in their livers.The histopathological changes of inculated duckling were observed.The result showed that the histopathological changes were orrhagic necrotic hepatitis,pancreas limitation coagulation necrosis.Particle resemble virus in membrane structure was shown about 30～40nm in diameter. The studies of physical and chemical properties about two strains showed: aether-resistant,chloroform-resistant,enzyme-resistant,heat,pH3.0-resistant and absent-aggiutination.