الفهرس 
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Abstract
One of the major problems of avian infectious bronchitis virus (IBV) is the frequent emergence of new variants. This research was conducted to survey of the presence of IB outbreak in 26 different chicken farms located in 8 governorates include ( Dakhlia, Gharbia, Sharkia, Behira, Giza, Ismaelia, Port said and Qaliobia) during 3 years from 2012 -2014 and included broiler, breeders and layers. The chickens were suffered from respiratory signs ranged from slight to moderate and decrease in egg production Examination of 26 pooled of samples includes trachea, kidney, lung and oviduct by real time RT- PCR , revealed 23 samples were positive for IBV. The 500-bp of the S1 gene covering the hyper variable region-3 of 8 selected isolates were amplified and sequenced. Phylogenetic analysis revealed that these viruses were separated into three groups, the first group is classic groups which included Giza F118-7/2013 resembled H120 vaccinal strains of IBV, the second groups (Port said F118-4/2013-Giza F 299/2013 and Qaliobia F1006/2014) resembled Variant2 IS/1494 and the third groups ( Dakahlia F247/2013 and Qaliobia F1006 /2014) resembled vaccinal strain D274. Although all farms in this experiment were vaccinated by classic strain of IB as commercial live (IB -H120 / MA5 ) vaccine or inactivated vaccine, that is provide little to poor protection against new IB serotypes that have been circulated and isolated recently and lead to outbreaks in various governorates in Egypt. It is necessary to monitor the evolving IBV strains in order to set up an effective control and strategy of the disease in Egypt.