Isolation and Characterization of Fowl Adenoviruses Associated with Hydro-pericardium Syndrome from Broiler Chickens in Egypt

One of the most prominent viral diseases affecting the poultry industry is hydropericardium syndrome caused by fowl adenoviruses. Hydropericardium syndrome has recently led to significant economic losses in the Egyptian poultry sector. Many outbreaks of hydropericardium syndrome have been documented across the country in the last few years. This research examined the epidemiology and molecular characterization of fowl adenoviruses in broiler chickens in Egypt. Samples were taken from 26 outbreaks of commercial broiler chicken farms in the Beheira and Menofia governorates, Egypt, from January 2021 to March 2022. Adenoviruses genomes were detected in cloacal swabs of 10 flocks using polymerase chain reaction. Clinically, infected broiler chickens (Cobb, Ross, Indian River, Modified-Avian, and Arbor Acres) showed depression, ruffled feathers, retarded growth, and ascites, with mortality rates of 10-28%. The most common postmortem lesions were hydropericardium, yellowish enlarged liver with ecchymotic hemorrhages, pancreatitis, and enteritis. Histopathologically, intranuclear inclusion bodies, commonly basophilic type, were scattered in the hepatocyte, proventriculus, duodenum, kidney, pancreas, and spleen. In addition, depletion of lymphocytes in the bursa of Fabricius and the thymus was observed. Seven samples were selected for gene sequencing of the loop 1 region of the hexon gene. The sequence analysis revealed that all samples were identical and similar to fowl adenoviruses species D serotype 2/11, suggesting that this serotype was the predominant fowl adenoviruses circulating in the study location in the last two years. Further studies are required to address the pathogenicity of isolated fowl adenoviruses and evaluate the vaccine used to control fowl adenoviruses in Egypt. Keywords: Fowl adenoviruses, Hexon, Hydropericardium syndrome, Phylogenetic analysis, Polymerase chain reaction