Incidence of Hepatitis Hydropericardium Syndrome in Broiler Chickens Caused by a New Fowl Adenovirus Strain in Iraq

Hepatitis Hydropericardium syndrome (HHS) is an acute infectious disease affecting broiler chickens. It is caused by a fowl adenovirus (FAdV) of Group I, serotype 4. This disease is characterized by sudden deaths in broilers as young as three weeks, with mortality rates reaching up to 65%. The current study aimed to evaluate the outbreak of HHS in three broiler farms in southern Iraq. It also sought to identify the specific serotypes of fowl adenovirus (FAdV) responsible for this outbreak, primarily focusing on its genetic characteristics and diversity. Ten liver and heart tissue samples were collected from broiler chickens (Ross 308) that had displayed clinical signs of depression, ruffled feathers, and a tendency to huddle in corners before death. Viral DNA was extracted from liver tissues for further virus detection using PCR and RT-PCR. A post-mortem examination showed a turmeric-yellow discoloration in the dividing lines between the pectoral muscles and the abdominal cavity. The livers of infected chickens were markedly enlarged, and clear, yellow-colored fluid was observed in the pericardial sac. Histopathological analysis of stained liver and heart tissues revealed small multifocal areas of necrosis and mononuclear cell infiltration, including basophilic intranuclear inclusion bodies in hepatocytes and lymphocytic infiltrates. Conventional PCR analysis of liver tissues confirmed the presence of FAdV serotype 4, identifying all samples as the Melad strain, a novel strain responsible for the ongoing epidemic in Iraq. This study confirmed the presence of FAdV serotype 4 and identified all samples as the Melad strain. This research also addresses the need to investigate FAdV with molecular techniques for a better understanding of the epidemiology of the disease.