Objective A disease model of fowl adenovirus serotype 2 (FAdV-2) was established to provide a refference for evaluating the immunogenicity and vaccine effectiveness of FAdV-2.

Method The samples suspected to be infected with avian adenovirus were isolated and identified. The genetic evolution of the Fiber and Hexon gene sequences of the isolates was analyzed. The nucleotide and amino acid sequences of the isolated strain and other FAdV representative strains were analyzed using DNAStar and MEGA7.0. After determining that the isolated virus was FAdV-2, the pathogenicity of the isolated strain was analyzed in 6-week-old SPF chickens under different infection routes and different infection doses in animal experiment. The best infection model and infection dose were selected to establish the FAdV-2 pathogenesis model.

Result One FAdV-2 strain was successfully isolated from the infected chicken tissue samples, named KM strain. Genetic evolution analysis shows that KM strain and GX01 strain belong to the FAdV-2 of avian adenovirus species D of group Ⅰ. The homology analysis shows that the nucleotide similarity of Fiber gene and Hexon gene between KM strain and GX01 strain is 98.9% and 99.3%, and the amino acid similarity is 98.9% and 98.8%, respectively. The pathogenicity of intravenous injection was higher than that of intramuscular injection, and the chickens showed obvious hepatitis hydropericardium syndrome (HHS). The infection route of the KM strain model was intravenous injection, and the infection dose was 10^8.0TCID₅₀. The chickens died after infection, with a mortality rate of 50%. Obvious pathological changes were found in the dead chickens at necropsy, and the chickens were positive for cloaca virus shedding at 1 d post infection. The established KM strain disease model provides a certain reference for vaccine development and vaccine evaluation, which will effectively prevent and reduce the transmission of FAdV-2.

Conclusion It is verified that FAdV-2 can cause hepatitis hydropericardium syndrome, and a pathogenesis model of FAdV-2 infection in SPF chickens is established for the first time.