1. Avian Disease Division, National Veterinary Research and Quarantine Service, Anyang 430-757, Korea.
2. Avian Disease Laboratory, College of Veterinary Medicine, Konkuk University, Seoul 143-701, Korea.
3. Sam Hwa Breeding Agri, Boryeong 355-813, Korea.
4. Merial Korea, Seoul 137-040, Korea.