A 474-base pair segment covering the hypervaible region of VP2 gene from six Korean infectious bursal disease virus(K-IBDV) isolates(K1, K2, SH/92, 225, 269, 310) and one attenuated IBDV(DAE) were amplified using RT-PCR, sequenced, and compared with published sequences for IBDV. K-IBDV isolates(K1, K2, SH/92, 225, 269) and foreigh very virulent(vv) IBDV strains had 94.93-100% amino cid sequence similarity. K-IBDV isolate 310 and other K-IBDV isolates had 84.31%-86.07% amino acid sequence similarity. Attenuated strain(DAE), like other attenuated strain, has substitution at positions 279(D to N) and 284(A to T) as well as in the serine-rich heptapeptide region. Five K-IBDV isolates except 310 isolate share unique amino acid residues at positions 222(A), 256(I), 294(I) which are not present in other standard and attenuated strains. At the two hydrophilic region, K-IBDV isolates except 310 isolate had identical amino cids comparing with Belgium vv IVDV 894VB but had four amino acid substitutions comparing with Chinese vv IBDV F9502. The SWSASGS heptapeptide is conserved in all KIBDV isolates. The sequence of K-IBDV isolate 310 was markedly different from other IBDV strains, evolving from a separate lineage than the others. By phylogenetic analysis, Five K-IBDV isolates except 310 isolate were categorized in one group with foreign vv IBDV isolates but K-IBDV isolate 310 was categorized ina separate group which was differentiated form other compared IBDV strains.

Brain, spleen, and selected lymph nodes from sheep with clinical signs of scrapie were analyzed for presence of proteinase K-resistant protein (PrP-res). Diagnosis of scrapie on the basis of detection of PrP-res was compared with diagnosis on the basis of histologic evaluation of the brain from clinically affected or exposed sheep. Proteinase K-resistant protein was found in every brain that was histologically positive for scrapie, and in addition, was found in the brain of several clinically positive sheep that were not diagnosed as scrapie-positive by histologic evaluation. Proteinase K-resistant protein was also found in 87% of the spleens and lymph nodes from sheep that had PrP-res detected in brain homogenates. Therefore, analysis of sheep brain, spleen, or lymph nodes for PrP-res provided a diagnostic approach that was superior to histologic examination alone for detection of naturally scrapie agent-infected sheep.

Bovine viral diarrhea (BVD) is very important disease in cattle industry with a worldwide distribution. Detection and elimination of persistently infected calves with bovine viral diarrhea virus (BVDV) was valuable strategy for BVD eradication because those calves were main source for transmission. We surveyed persistent infection with BVDV by reverse transcription polymerase chain reaction (RT-PCR) and immunohistochemistry (IHC) using whole blood and skin. Five hundred thirty nine Korean native calves were tested. Four calves (0.7%) were positive for BVDV antigen for both tests.

Field infectious bursal disease viruses 9IBDVs) were isolated from IBDV-suspected commercial chickens. The variable region in VP2 gene of six Korean IBDV isolates (K-IBDVs) and IBD vaccines was examined using the reverse transcriptase/polymerase chain reaction-restriction fragment length polymorphism (RT/PCR-RFLP) assay. With all K-IBDVs and vaccine IBDVs, a 474-bp fragment of the VP2 gene was amplified and tested with various restriction enzymes. Resseriction enzymes BstNI and StyI differentiated K-IBDV isolates and IBD vaccines into four groups. Reseriction enzyme profiles of K-IBDV isolates were different from them of IBD vaccines. K-IBDV isolates except for 310 isolate had specific SspI and TaqI recognition sites, which were recognized in highly virulent IBDVs, but IBD vaccines had no those sites. This study showed that RT/PCR-RFLP assay was thought to be valuable tool for differentiation of IBDVs and identification of highly virulent IBDV.