GENETIC CHARACTERISTICS OF INFECTIOUS BURSAL DISEASE VIRUS IN EGYPT FROM 2012 TO 2014

The infectious bursal disease virus (IBDV) is a continuing serious problem facing poultry industry in Egypt. In this study, 24 bursae samples collected from different broiler flocks (from Giza, Dakahleya, Ismailia, Damietta and Alexanderia) experiencing high mortality rate and bursal lesions during 2012 to 2014 were examined. Clear differences in pathotyping between very virulent Infectious bursal disease (vvIBD) and classical IBD were observed in pathological examination. Reverse transcriptase polymerase chain reaction (RT-PCR) was applied for IBD targeting hyper variable region (HVR) of VP2 gene. Genetic analysis revealed that 15 viruses belonged to vvIBD that had amino acids A222, I256, I294 and S299 which are highly conserved among vvIBD starins, while 9 viruses belonged to classical IBDV (similar to vaccine strains). The genotyping of Egyptian vvIBDV indicate progressive evolution compared with previously isolated strains which indicates persistence of vvIBDV in Egyptian poultry environment.