PATHOLOGY AND MOLECULAR DETECTION OF INFECTIOUS BRONCHITIS VIRUS INFECTION IN BROILER CHICKENS

Abstract

Infectious bronchitis is a highly contagious viral disease of chickens, causing significant economic losses in Egyptian chicken farms. In this study, we surveyed the prevalence of infectious bronchitis virus infection in broiler chicken flocks in Assiut Governorate as well as description of its pathological lesions. Pooled samples were collected from 22 broiler chicken flocks suspected to be infected with infectious bronchitis virus. Ten samples were confirmed to be positive for infectious bronchitis virus infection using RT-PCR. Nasal discharge, coughing and gasping were the main signs. Grossly, chickens showed hyperemic trachea with a caseous plug at the bifurcation of the trachea. The kidneys appeared congested and enlarged. Trachea, lungs and kidneys specimens were collected for histopathological examination. Tracheal specimens were also collected for electron microscopy study. Microscopically, the trachea showed complete loss of the epithelial cilia, associated with either necrosis or metaplasia of the lining epithelium. The lungs revealed hemorrhagic pneumonia, necrosis of the bronchial epithelium and thickening in interalveolar tissue with inflammatory edema. The kidneys exhibited swollen glomeruli with hypercellularity, necrosis of renal tubules and severe interstitial hemorrhage. Scanning electron microscopy of the trachea revealed severe deciliation, leaving very short microvilli on the mucosal surface. Transmission electron microscopy demonstrated the presence of viral particles in the epithelial lining. So, despite routine vaccination, IBV is still spreading within broiler flocks in Assiut Governorate, causing severe losses and pathological lesions. This requires further investigation of the immune profiling of these broiler chicken flocks.