Epidemiological Study Of Tianjin FAV-4TJ1607 Strain And Effect Of Emmunopotentiator On Immune Efficiancy To The Inactivated Vaccine

Hydropericardium-Hepatitis syndrome(HHS),also known as avian Ankara disease,first appeared in the Ankara region of Pakistan in 1987 and was caused by a group I type 4 avian adenovirus(FAV-4)strain.Highly pathogenic FAV-4 can infect a variety of poultry,and birds of all ages are susceptible to it,causing huge economic losses to the poultry industry.Since 2015,HHS has occurred nationwide.In 2016,the FAV-4 TJ1607 strain was firstly isolated from the liver of a naturally-occurring chicken in a chicken farm in Tianjin by Wang Jing.To investigate whether the FAV-4 TJ1607 strain can be transmitted vertically,and to verify the difference between the yolk and serum antibody titers.Twelve30-week-old healthy laying hens were artificially inoculated with FAV-4 TJ1607 strain,respectively,1d,2d,3d,4d,5d,7d,9d,11 d,13d,15 d,17d,19 d,21d,23 d after challenge The serum and yolk antibody titers were tested.The results showed that the positive antibody appeared on the 5th day of the serum,the positive antibody titer was the highest on the 17 th day,the positive antibody appeared on the 7th day of the yolk,and the positive antibody titer was the largest on the 19 th day,compared with the serum antibody result.The yolk positive fit rate was 29.7%,the negative fit rate was63.3%,and the total fit rate was 93.0%.The yolk antibody and serum antibody showed no significant difference on the 7th day and beyond,indicating that the serum can be replaced by yolk.Detection of antibodies.In order to continue to understand the prevalence of FAV-4 TJ1607 strain in Tianjin farms,this study collected six different ages in Tianjin,Wuqing District,Xiqing District,Beichen District,Jinghai County,Baodi District and Qixian County.A total of 10 samples of the variety were diagnosed by clinical consultation,necropsy observation,histopathological examination,PCR examination,and ELISA.The results showed that 5 of the 27-day-old AA broilers in Jixian County had avian pericardial effusion-Hepatitis syndrome,6 of the 8-day-old Rose 308 broilers in Jixian County were in the stage of recessive infection.The FAV-4 TJ1607 strain was not detected in other regional farms,indicating that various chicken farms in Tianjin began to attract attention and prevent the disease.The immunization program and feeding management measures are relatively complete.The differences in immune efficiency between Chicken Transfer Factor(CTF)group,Astragalus Polysaccharide group,Lycium Extract Polysaccharide group and control group were compared for exploring the effect of three immunopotentiators on the immune efficiency to FAV-4 TJ1607 strain inactivated vaccine.Forty healthy chicks post-injected with FAV-4 TJ1607 strain inactivated vaccine were randomly divided into 4 groups before bleeding for basic FAV-4 antibody detection.Blood samples were taken on odd days for detection of group I avian adenovirus type 4antibodies.The results showed that the antibody titer of the chicken transfer factor group was significantly different on the 13 th day,and it maintained a growing trend.The antibody titer of the Astragalus polysaccharide group showed significant difference on the 17 th day and remained at a high level.Antibody titers showed significant changes on day 19 and remained at a high level.It indicates that the synergistic effect of chicken transfer factor is the strongest,and it can be used preferentially.Astragalus polysaccharide is the second,and polysaccharides are used as appropriate.