Identification of infectious bursal disease viruses from RNA extracted from paraffin-embedded tissue.

After histopathologic screening of bursas of Fabricius for the presence of infectious bursal disease virus (IBDV) lesions, the hypervariable region of the VP2 gene for IBDV was extracted from formalin-fixed paraffin-embedded tissue blocks. With real-time reverse transcription-polymerase chain reaction (RT-PCR) and sequencing, IBDV was identified in 227 different blocks. The ability to identify the actual virus strain associated with the lesions observed microscopically in the bursa of Fabricius allowed for direct correlation between viral identity and lesions, which may help in designing vaccination strategies. Several new emerging viruses that do not group with other known IBDVs in phylogenetic tree analysis were identified, as well as a unique variant virus that had 63 nucleotides missing from its hypervariable region.