1. Department of Infectious Diseases and Avian Diseases, College of Veterinary Medicine and Korea Zoonosis Research Institute, Chonbuk National University, 79 Gobongro, Iksan, 570-752, South Korea
2. These authors contributed equally to this study
3. Poultry Science Division, National Institute of Animal Science, Rural Development Administration, 114 Shinbang 1-gil, Cheonan, 331-808, South Korea