Abstract

Infectious bronchitis virus (IBV) is a highly transmissible avian Gamma-coronavirus that continues to pose a major challenge to poultry health and productivity worldwide, particularly in broiler production systems. The present investigation aimed to detect and characterize IBV infections in broiler flocks located in two districts of Southern Iraq between late 2024 and early 2025. A total of 200 clinically affected broilers (100 broilers from each flock) were sampled, with tracheal and kidney tissues collected for clinical evaluation, histopathological assessment, and viral isolation. Suspected IBV-infected chickens showed respiratory distress, increased mortality, and kidney lesions. The suggestive post-mortem lesions were caseous plug exudates at the tracheal bifurcation, as well as congested and hyperemic kidneys. The inoculation of tracheal and kidney tissue suspension in embryonated chicken eggs (ECEs) resulted in death, stunting, curling, dwarfism, congestion, and subcutaneous hemorrhages. The histopathological findings in tracheal tissues revealed epithelial desquamation, goblet cell depletion, and lymphocytic infiltration, while kidney findings exhibited tubular degeneration, glomerular disruption, and fibrin deposition. These findings emphasize the need for future studies to focus on the molecular identification of circulating strains, vaccine matching, and monitoring of post-vaccination protection levels in Iraq.