Exploring Hydropericardium Hepatitis Syndrome (HHS) in Broiler Chickens: A Comprehensive Clinical and Histopathological Study in Diyala Governorate

Abstract

Hydropericardium Hepatitis Syndrome (HHS), caused by Fowl Adenovirus serotype 4 (FAdV-4), is a significant viral disease in broiler chickens, leading to high mortality and substantial economic losses in the poultry industry. It primarily affects chickens aged 3 to 6 weeks, characterized by the accumulation of amber-colored fluid in the pericardial sac, distinguishing it from other adenoviral diseases like Inclusion Body Hepatitis (IBH).This study, conducted at the College of Veterinary Medicine, University of Diyala, aimed to identify FAdV-4 strains associated with (HHS) and confirm the presence of HHS in Diyala Governorate. To achieve this, tissue samples from 50 post-mortem cases across five regions Baqubah, Al-Galibia, Al-Khalis, Kanaan, and Baladrose were collected from clinically infected chickens, including liver, spleen, kidney, heart, and intestine. All samples were preserved in 10% formalin and processed for histopathological analysis. Clinical signs observed in infected chickens in the current study, included depression, reduced feed intake, and discolored excreta. The excreta of affected chickens showed discoloration, ranging from deep yellow to greenish, indicating intestinal distress. Post-mortem lesions were characterized by pericardial effusion, with clear or amber-colored fluid in the pericardial cavity, which was the most prominent lesion. Additional findings included enlarged, friable liver with areas of necrosis, congested kidneys with urate deposits, and splenomegaly. Histopathologically, the liver exhibited dilated central veins and sinusoids, with infiltration of polymorphonuclear and mononuclear cells, along with necrotic hepatocytes. The kidneys displayed severely dilated tubules packed with proteinaceous debris and widespread interstitial edema. The heart showed signs of myofiber necrosis, lymphocytic