1. National Veterinary Research and Quarantine Service, Ministry of Agriculture & Forestry, Anyang 430-824, Korea.
2. College of Veterinary Medicine, Kyungpook National University, Daegu 702-701, Korea.
3. College of Veterinary Medicine, Chonnam National University, Gwangju 500-757, Korea.
4. Daegu Metropolitan City Research Institute of Health & Environment, Daegu 706-732, Korea.