Pathogenicity of Avian Adenoviruses Type D and Type E Isolated from Field Cases of Inclusion Body Hepatitis–Hydropericardium syndrome (IBH–HPS) in Broiler chickens in Egypt

Abstract

In this study, 210 one-day-old commercial broiler chicks were used to investigate the pathogenicity of two types of Avian Adenoviruses (type D and type E) recently isolated from field cases. These chicks were divided into four groups; birds of group 1 (G1) and group 2 (G2) were experimentally inoculated with two local isolates of fowl aviadenovirus FAdV D-2 and FAdV D-11, respectively, while chicks of group 3 (G3) were experimentally inoculated with FAdV-E 8a. All birds of these three groups were experimentally inoculated orally at one-day of age with a dose of 0.5mL (107 TCID50/mL). Birds of group 4 (G4) served as uninoculated blank controls. Clinical signs, gross lesions and histopathological changes were examined at different intervals post inoculation. Birds of all infected groups showed hydropericardium, focal hepatic necrosis and ecchymotic hemorrhage of thigh and breast muscles. Hepatitis, glomerulonephritis, pericarditis, myocarditis and lymphoid depletion in the spleen were the main histopathological observations. Mortality rates of 12, 16 and 6% were observed in chicks of G1, G2 and G3, respectively, indicating that FAdV-D isolates were more virulent than FAdV-E. Hemagglutination inhibition test revealed significant decrease in antibodies titers against inactivated NDV vaccine in birds of the three FAdVs infected groups compared to the chicks of the control group. In Egypt, several studies reported Adenoviruses infections in broilers; however, to our knowledge this is the first study in which the pathogenicity of FAdVs isolates has been reported. It was concluded that FAdV-D 2, FAdV-D 11 and FAdV-E 8a are primary agents, in addition to possibility of these isolates to act as neglectable immunosuppressive agents incriminating to vaccination failure in chickens.