Molecular and Pathological Investigation of Infectious Bronchitis in Broiler Flocks in Sulaimani Province, Iraq

Abstract

This research's goal was to examine the molecular analysis and pathological lesions linked to IBV infection in flocks of naturally infected broiler chickens from non-vaccinated and vaccinated (H120, MA5+IB 4-91) flocks. One hundred sixteen birds were collected in Sulaimani provinces between November 2021 and July 2022 from various broiler chicken flocks of vaccinated (H120, MA5+IB 4-91) and non-vaccinated birds who suffered from respiratory illness. Viral isolation and PCR were used to confirm the infection. The majority of the necropsied birds showed congested trachea and the presence of mucus with caseated debris at the bifurcation. There was a white precipitate in the ureters, also the kidneys were enlarged and congested. Sequencing of the S1 glycoprotein gene revealed that four isolates found and after phylogenetic analysis of the strains' deduced amino acid sequences indicated that they had a close relationship with the Iranian strains MG013972 and MG013973 as well as the Iraqi strain MH747093. The non-vaccinated chickens' histopathological evaluation of all organs was more severe than that of the vaccinated chicks, with catarrhal exudate obstructing the tracheal lumen and tracheal epithelium undergoing hyperplasia to squamous metaplasia. In lung sections, catarrhal exudate partially to completely blocked the parabronchial lumen and the intrabronchial septa thickened due to alveolar capillary congestion, and an inflammatory reaction. Mild to severe glomerulonephritis with considerable collecting epithelial cell degeneration was seen in the kidney segment. Finally, it can be said that the infectious bronchitis virus is a significant contributor to the respiratory and/or renal issues affecting the flocks of broiler chickens in Sulaimani Province.