الفهرس 
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Abstract
Re-emergence of highly virulent forms of IBDV has been the cause of significant economic losses. In present study, bursal samples were collected from fifty broiler chicken farms across six different governorates during 2010-2012 which were showing IBDV clinical signs and postmortem findings. Fifty bursa homogenates representing the fifty investigated farms were assayed using reverse transcriptase-polymerase chain reaction (RT-PCR) for IBDV targeting VP2 gene. Out of the tested samples 9 were positives. IBDV-positive samples were selected for further isolation and characterization. The virus was isolated by inoculating bursa suspension into embryonated specific pathogen-free (SPF) eggs. Chorioallantoic membrane(s) (CAMs) were collected and tested by AGPT confirming the presence of IBDV. The virus was detected by RT-PCR and sequence analysis of PCR products of 9 selected samples was carried out. Four samples were characterized as very virulent (vvIBDV) and five samples were classic attenuated IBDV similar to classic attenuated (vaccine) strains. The genotyping of Egyptian vvIBDVindicate continuous evolution of IBDV in Egypt and they were closely related to previous isolated strains from Egypt.