1. Department of Infectious Diseases, College of Veterinary Medicine, Seoul National University, Seoul 08826, Korea.
2. Department of Animal Science & Technology, Suncheon National University, Suncheon 57922, Korea.
3. National Institute of Animal Science, Rural Development Administration, Pyeongchang 25340, Korea.
4. Department of Veterinary Pathology, College of Veterinary Medicine, Seoul National University, Seoul 08826, Korea.