Diagnosis and histopathological study of avian influenza virus-H5 (AIV-H5) in broiler farms

Abstract

This study was conducted for diagnosis and description of the pathological changes of AIV-H5 as the causative pathogen in Iraqi broiler farms. The current study was carried out on 84 broiler farms. Infected birds were tested for detection of the AIV infection from the tracheal swabs by rapid chromatographic AIV type A and H5 test kits. In RRT-PCR 8 samples (8 farms) of Trachea were selected to be tested by this assay. Samples of trachea, lung, and spleen from the dead birds with natural AIV-H5 infection were submitted for histopathological examination. seventy-two out of 84 farms tested for AIV-Type A gave positive results, and 58 out of 72 positives for type A-AIV gave a positive result for H5 antigen in a rapid chromatographic strip. The main gross lesions in the trachea of infected birds were severe congestion and hemorrhage. In the RRT-PCR assay, 8 out of 8 samples gave a distinct positive result for this test. The microscopic histopathological examination of infected tracheas showed obvious desquamation of lining epithelium with complete loss of cilia associated with congestion of blood vessels in lamina properia. Infected lungs revealed diffuse alveolar damage and severe multifocal vascular congestion. There was deposition of fibrinous material in the splenic tissue associated with the disappearance of the germinal centers. Thus, we concluded that AIV-H5 infection causes severe pathological and histopathological changes as a result of systemic infection. The RRT-PCR assay was highly sensitive and specific for the detection of highly pathogenic avian influenza virus subtypes.