Development Of The Inactivated Vaccine And Yolk Antibody For Serotype 4 Group Ⅰ Of Fowl Adenovirus

Group I serotype 4 fowl adenovirus(FAdV-4)can cause hydropericardium-hepatitis syndrome(HHS).Since 2015,HHS has occurred and prevailed in Henan,Hebei,Shandong,Jiangsu,Anhui,Guangdong and other places in China.It can occur in broilers,laying hens and three yellow chickens,etc.,with rapid transmission speed and high mortality,bringing serious economic losses to the chicken industry.In this study,virus was isolated from clinical cases and inactivated vaccine and yolk antibody were prepared to provide technical support for the effective prevention and control of the disease.1.The isolation,identification and pathogenicity test of FAdV-4In 2015-2018,pathogens were isolated and identified from clinical cases of suspected HHS from Shandong,Hubei,and Hebei.Then,infection the SPF chickens embryo、1 day and 21 days SPF chickens respectively with the isolated strains.Histopathology and PCR were used to detect the pathological changes,virus distribution and detoxification of various tissues and organs.The results showed that all the chicken embryos were died at8 dpi and typical lesions such as hydropericardium and hepatomegaly and hemorrhage occurred at 6dpi.All the 1d SPF chickens were died at 4dpi,and 21 d SPF chickens and cohabitation chickens had a mortality rate of 60%;The main pathological changes were in liver,heart and kidney,and the virus DNA was detected in liver,heart,spleen,pancreas,small intestine and kidney.Cloaca detoxification was detected at 3,5,7 and 14 dpi in chickens infected at 21 d infected chickens.Oral detoxification was detected at7 and 14 dpi,.The results showed that the strain was highly infectious,highly lethal,certain panophilia,and strong horizontal transmission ability.Cloacal detoxification was the main detoxification method.2.Development of inactivated vaccine for FAdV-4The strain with high immunogenicity was screened from the isolated strains to prepare the oil-inactivated vaccine,and the 21-day-old SPF chicken was inoculated with the vaccine.After 3 weeks,the two strains were used to attack the virus;the detoxification and The distribution of the virus were detected with the PCR method;the content of antibodyand interleukin-2 was monitored by ELISA.The results showed that there was no death in the chickens in the immune challenge.No detoxification was detected at 3,5,and 14 dpi.Only a small amount of detoxification was detected at 7 dpi.No virus DNA was detected in all organs of the surviving chicken at 14 dpi.At 2 weeks,the antibody level gradually increased,and began to decline after infection.By the fifth week,the antibody level began to rise;the interleukin-2 content changed little in 2-3 weeks before infection,and the interleukin-2 content increased significantly at 7dpi.The results showed that the vaccine has good immunogenicity,which take the body strong resistance to infection of both strains.3.Preparation and application of egg yolk antibody of FAdV-4Egg yolk antibody was prepared using the above vaccine with immunization healthy commercial laying hens,then,intramuscularly injected into SPF chickens.Two days later,infected the isolates Fadv-4 viruses and detected the distribution and detoxification of the virus.The results showed that the mortality rate of the 14 dpi test group and the control group were 6.67% and 60%,respectively(P<0.01 was extremely significant).In the test group,only the liver could detect the DNA of the virus,while in the control group,the heart,spleen,pancreas and all other organs could be detected.Only sporadic detoxification was detected at 7dpi in the experimental group,and detoxification was detected at 3-7dpi in the control group.It showed that the prepared egg yolk antibody can effectively neutralize the virus,restrict its infection to the liver,inhibit the body’s detoxification,and provide effective protection for SPF chicken.In summary,the isolated strains of this experiment were highly pathogenic and had certain panophilia.The cloaca detoxification was the main detoxification method;the prepared inactivated vaccine and yolk antibody can effectively protect SPF chickens to resistance the FAdV-4 infection.