This study was conducted to characterize infectious bursal disease virus (IBDV) isolates collected from different parts of Iran during 2005-2006. Pooled bursal samples from 49 broiler and layer pullet flocks suspected to IBD infection were collected and processed. A reverse transcriptase-polymerase chain reaction (RT PCR) procedure was used to amplify a VP2 gene fragment (743 bp) from IBDV field isolates. Amplified VP2 fragments were further characterized by two restriction enzymes, BspMI and SacI. From 49 field samples, 37 (75.5%) samples were IBDV positive by RT PCR. Digestion with two restriction enzymes, BspMI and SacI, showed patterns compatible with very virulent IBDV and classical IBDV strains in 34 (91.9%) and 3 (8.1%) IBDV-positive samples, respectively. The restriction enzyme analysis of this study was comparable to that of other isolates and reference strains with available nucleotide sequence data in the GenBank. The procedure followed in this study is a useful method to rapidly differentiate the very virulent IBDV and classical IBDV isolates.

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