The infectious bronchitis virus has been identified as a highly contagious disease in chickens. The molecular characterization and pathological lesions linked to IBV infection[SA1]  in naturally infected flocks from 7 Egyptian provinces from 2019 to 2022 were investigated in this study using the tissue samples from 18 broiler chicken flocks suspected of having respiratory disease. The reported isolates were detected by a real-time reverse transcriptase assay that targeted the s1 gene (HVR1-2), and they were characterized further by (S1) gene sequencing with histopathological examination of kidney and tracheal tissue. Phylogenetically, the S1 gene was clustered into two major groups, The first group had only one virus belonging to the classical vaccine strain of GI-1 lineage, it had a specific character of 32 Amino Acids (AA) mutations compared to EU780077-IS/1494/2006 reference strain and the second group contains 9 viruses belong to genotype GI-23 (variant II). They were further separated into two subgroups, The first subgroup GI-23.2.1, contains 8 viruses with 7-14 Amino Acids (AA) mutations, second subgroup contains one virus belonging to genotype GI-23.2.2 which has 18 AA mutations, compared to EU780077-IS/1494/2006 reference strain, specifically in HVRs regions (HVRI, II). The histopathological examination revealed degenerative changes and loss of cilia of the tracheal epithelium. The kidneys had necrosis with heterophil infiltrations, congestion, and tubular degeneration. In conclusion, the current study investigates the Characterization and Pathotyping[DDM2] of the infectious bronchitis virus in some Egyptian flocks. It is critical to ongoing monitoring to stop the spread of infections, as well as the creation and use of vaccines based on local viruses.



 [SA1]




 [DDM2]Not including in the aim of the work