Diagnosis of Different Strains of Infectious Bronchitis of Broilers With Polymerase Chain Reaction (PCR) In Dakahlia Governorate

Infectious bronchitis virus (IBV) is one of the most important viral diseases of poultry, it causes major economic losses to poultry industry. New IBV geno- and serotypes are continually reported from all over the world and especially from Egypt. This study was conducted to investigate the prevalence of different strains of (IBV) in commercial broiler flocks in Dakahlia governorate. Fifty birds suffering from respiratory disease were collected from five farms. These birds were necropsied and examined for the Presence of pathological changes in trachea, lungs, kidneys, spleen and heart. Five Pooled samples of trachea, lungs, air sacs, heart and spleen and kidneys were tested for the presence of IBV, using the reverse-transcription polymerase chain reaction. Four of them were positive for IBV by RRT-PCR. Positive samples were amplified by RRT-PCR using specific primers for S1 gene.One was genetically characterized as IBV Variant 2 closely related to infectious bronchitis virus isolate Eg/12120s/2012spike glycoprotein (SP1) gene with identity homology of approximately 99% and Avian infectious bronchitis virus isolate IS/1494/06 spike glycoprotein gene, with identity homology of 96%.The second was genetically characterized as IBV Variant 2 closely related to Infectious bronchitis virus isolate Eg/12120s/2012 spike glycoprotein (SP1) gene with identity homology 95% and Avian infectious bronchitisvirus isolate IS/885 S1 spike glycoprotein gene, identity homology 93%. Tissue specimens from positive birds were prepared, stained and examined microscopically for histopathological changes and immunohistochemistry. Grossly, intense tracheitis with presense of mucus or caseous exudates could be seen inside trachea and respiratory airways beside focal pneumonic areas were common. Regarding histopathtological lesions, trachea showed intense catarrhal tracheitis accompanied by loss of cilia.Lungs revealed caseous plug inside primary bronchus .Air sacs showed air saculitis with pneumonia .Spleen had multifocal areas of coagulative necrosis. IBV antigen was detected by avidin biotin immunoperoxidase technique using IB Ab Igg prepared in chicken as primary monoclonal antibody. Dense brown granules were detected in lungs, trachea, kidneys and heart These results were consistent with virus detection by RRT-PCR and histopathological changes. Future work should include the isolation and serotyping of IBV in the region, so that a suitable vaccination program, using the common field serotypes as vaccines, can be adopted to protect against IBV caused disease