1. Import Risk Assessment Division, Animal and Plant Quarantine Agency, Anyang 430-757, Korea.
2. ISU Abxis Co., Ltd. Yonsei University Medical Center, Seoul 120-752, Korea.
3. Department of Infectious Diseases, College of Veterinary Medicine, Konkuk University, Seoul 143-701, Korea.
4. Veterinary Science Research Institute, College of Veterinary Medicine, Konkuk University, Seoul 143-701, Korea.