Rapid identification of "very virulent" strains of infectious bursal disease virus by reverse transcription-polymerase chain reaction combined with restriction enzyme analysis.

A reverse transcription-polymerase chain reaction (RT-PCR) combined with restriction enzyme analysis (REA) was developed for differentiation of classical virulent (cv) and very virulent (vv) strains of infectious bursal disease virus (IBDV). The VP2 gene was used for primer annealing to amplify the hypervariable region. An amplification product was obtained with serotype 1 and serotype 2 strains of IBDV.The restriction enzymes SacI and BspMI were used to identify and to differentiate the serotype 1 strains: SacI only cleaved cvIBDV RT-PCR products, whereas products obtained with vvIBDV strains were only cleaved with BspMI; serotype 2 strain products were not cleaved by either of these restriction enzymes. RT-PCR combined with REA as described in this study is thus suitable to detect IBDV of both serotypes and to distinguish rapidly between cvIBDV,vvIBDV and serotype 2 IBDV.Our investigation of a total of 11 different IBDV isolates and available nucleotide sequence data of other isolates indicate that the application of this protocol might be a useful tool for the rapid identification of vvIBDV isolates, a prerequisite for the effective control of this economically important virus infection of commercial poultry.