| Since June 2015,the clinical cases of Hydropericardium and Inclusion Body Hepatitis Syndrome emerged in many provinces of China which caused by fowl adenovirus.Most cases were observed in broilers of 3 to 5 weeks of age,and occasionally in layers and breeder pullets aged 10 to 20 weeks,lower mortality.Course of disease is 4 to 8 days after the onset of death,the duration of the disease is from 8 to 15 days.Mortality reported during these outbreaks varied from 30%increase to over 70%in severe cases resulting in greater economic losses to poultry industry in China.Ducks and geese were also reported in 2016.The pathogen of this disease is mainly fowl adenoviruses group I serotype 4 and as well as serotype 8.We studied the pathogenicity and immunogenicity of the two serotype 4 strains,on the basis of the culture amplification and analysis of the two serotype 4 strains isolated from the diseased chickens in our laboratory,to provide reference and help for the development of avian adenovirus vaccine.In order to increase the quantity of the fowl adenoviruses,we got the virus of material grinding fluid stored in this laboratory and inoculated to 7-day-old SPF chicken by yolk sac inoculation,0.2mL per embryo.They were inoculated blindly for three generations and allantoic fluids were collected on the basis of we need it markde PZ and HN.The dead chick embryo was mainly manifested by the development of chick embryo,compared with the same age healthy chick embryo inoculation,the chick embryo inoculated was significantly smaller,the body of the embryo curled,systemic bleeding,swelling and bleeding of the liver.Allantoic fluid without coagulation.Sequence analysis showed that there was a nucleotide mutation in Hexon gene of two strains,also PZ amino acid also mutated in 650.The homology of Hexon gene sequences of two strains was up to 99.9%which had the highest homology with serum serotype 4 virus.Forty-eight 29-day-old specific-pathogen-free(SPF)chickens,which were divided into eight groups,six per group,were used to determine the pathogenicity of two isolated strains,PZ and HN.SPF chickens were inoculated with the two isolated strains by intravenous injection or oral way,meanwhile designed the control group.Then the incidence and symptoms of chicken were observed in daily.Chickens inoculated were immediately found the incidence of death,then liver and other organs were collected to PCR detection and histopathological observation.The results of animal regression test showed that the clinical symptoms and the changes of biopsy were consistent with that infected by wild virus.Hydropericardium and Inclusion Body Hepatitis Syndrome were the characteristic syndrome of dead chickens.Viral DNA was detected in almost all tissues sampled from dead chickens by PCR,the difference lies in the destructive difference.There are a lot of fatty degeneration and basophilic inclusion bodies.The results of protective immunity test showed that two strains of PZ and HN are highly pathogenic,which can cause Hydropericardium and Inclusion Body Hepatitis Syndrome.To study the immunogenicity of adenovirus,we made inactivated oil emulsion vaccine with the highly pathogenic HN strain.Sixty 22-day-old specific-pathogen-free(SPF)chickens,which were divided into five groups,A,B,C,D,E,twelve per group.The first four groups were immunized group,inactivated oil emulsion vaccine(HN)were injected by intramuscular,each 0.8mL immuned.Group E was injected with sterilized PBS solution 0.5mL as blank control.The A,B,C,D groups were 0.2mL,0.3mL,0.5mL,0.8mL.We selected four each group randomly to challenge virus after taking blood injection 1,2,and 3 weeks after immunization,the amount of attack was 0.5mL.The results of protective immunity test showed that the clinical protection rate of maded by dominant serotype HN,which minimum immune dose for 0.8mL/only and three weeks after immunization,were 100%.All of the results showed that the oil emulsion inactivated vaccine owning a good immune protection. |
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