Pathogenicity Of Avian Adenovirus Type 4 Ⅰ Group In Different Day Old SPF Chickens

Hydropericardium hepatitis syndrome(Hydroperica rdium Hepatitis Syndrome,HHS),also called Angara(Angara)disease,which was a highly contagious disease caused by adenovirus of serum type 4,and it with characteristics of pericardial effusion and inclusion body hepatitis.As a previous report in Pakistan by Angola in 1987,the clinical symptoms of this neopathy was similar to that of inclusion hepatitis(Inclusion Body Hepatitis,IBH).Then the disease occurred in India,K uwait,Iran,Japan,Mexico and other countries subsequently.It was also been confirmed that the hydrocephalus hepatitis syndrome caused by serum type 4(Fowl Adenovirus serotype,FAV-4)in these countries.Since June 2015,Hunan,Jiangsu,Henan,Shandong,Hebei,Liaoning,Anhui,Jilin and other provinces of China,parts of the chickens there was a heart-shaped package can be caused by effusion and inclusion body hepatitis characterized serotype 4 infection of fowl adenovirus group I.Most of infected birds had an acute symptom,which usually occured in the 3-5 week old broilers.The death peak was 4-8 days after attacking and the course usually for 8-15 days,the mortality rate was 20%-80%.At present,the disease usually occured in chickens,hybrid hens and ducks,which made a serious threat to the health development of poultry industry in China.In this study,90 10-days-old SPF chickens were randomly divided into three groups(i.e.oral group,muscle group and control group).1mL(EID50 = 10-7.569/0.2mL)avian adenovirus type 4 inoculated through virus oral and muscle,respectively.1mL saline was inoculated in control group.Respectively after infection of 4d,8d,12 d,16d and 20 d weighing,sampling,and random killing poison attack group and control group with 5 rats in each chicken,the clinical symptoms and pathological changes were observed in infected chicken,observe pathological change by HE staining,serum biochemical indexes(ALT,AST,LDH,UREA),ELISA test set the serum cytokines(IL-6,IFN-γ)antibody titer and virus quantitative PCR detection in tissues.20 day old and 10 day old chickens had the same dose and the same method.Two day old chickens were challenged group showed depression,loss of appetite,body weight increased slowly,and the disease incidence of acute death,the mortality rate is high,10 day old muscle group the mortality rate reached 50%.Autopsy results showed that the 10 day old group of lesions and 20 days of age were similar,but more severe,pericardial effusion and inclusion body hepatitis significantly,spleen hemorrhage,pulmonary edema and hemorrhage,renal enlargement,thymus enlargement,bleeding,and 10 days of age group of glandular stomach bleeding.Histopathological results showed that there were obvious inflammatory cell infiltration in the liver and spleen of the experimental chickens,and the myocardial interstitial edema was widened.The biochemical indexes showed that the contents of ALT,AST,LDH and UREA increased after the attack,and were significantly higher than those in the control group.The results showed that the contents of IL-6 and IFN-were increased after the attack.The results of detection of antibody in serum showed that the antibody in the attack group was on the rise,and was significantly higher than that in the control group.The detection results of tissue viral load,oral inoculat ion group and muscle inoculation group of heart,liver,spleen,lung,kidney,pancreas,thymus and bursa tissues were detected in the presence of the virus,the viral content in heart and liver was higher,and the viral load of organs in muscle attacking group was higher than that in oral toxicity group.FAV-4 can damage the chicken’s multiple organs,resulting in the incidence of chicken,in the absence of maternal antibodies and other virus interference,the infection of the disease after the small day old chicken than the large day old chicken lesions more serious.In conclusion,the pathogenic capability of was associated with the day post infection(dpi)and the route of inoculation,young birds were more susceptible to the virus than old one,and the damage of muscle group was more serious than that of oral group.The virus could infringe on the multiple organ of the host,the virus has a wide distribution in the organization.