Background: Infectious bursal disease virus (IBDV) remerged frequently in Egypt, causing serious economic losses. In Egypt very virulent (vv) IBDV strains are annually reported since its first introduction in 1989. Variant IBDV strains were also reported in few studies. To date, IBDV associated with breaks has been characterized in flocks which were vaccinated with classical IBDV vaccines and demonstrated IBD characteristic lesions.
Objectives: In present study the aim was to molecular characterize IBDV field strains detected in flocks located in 4 governorates. Also, a phylogenetic analysis based on the sequence of the hyper variable region of VP2 gene was carried out.
Methods: Forty field bursa samples were collected from different localities. IBDV was detected using RT-PCR. Sequence analysis of the variable region of VP2 gene purified from the PCR product. Comparative phylogenetic analysis based on the sequence of the hyper variable region of VP2 gene as well as phylogenetic tree was constructed along with local and reference IBDV strains using DNAstar MegAlign software.
Results: Eight out of 40 samples were positive for IBDV with RT-PCR, Comparative phylogenetic analysis based on the sequence of the hyper variable region of VP2 gene showed that the characterized strains were closely related to IBDV Giza 2008 strains.
Conclusion: this study reports the continuous circulation of vvIBDV strains in vaccinated flocks 4 governorates Giza, Sharkia, Behira, and Dakahlia, in Egypt during year 2015. There are need to review the control strategy and the vaccination failure of IBDV in broiler flocks specially the extensive abuse of using classical vaccines.
Key words: IBDV, RT-PCR, VP2, Sequencing, phylogenetic analysis
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