1. The United Graduate School of Veterinary Sciences,Gifu University, 1-1 Yanagido, Gifu 501-1193,Japan
2. Laboratory of Zoonotic Diseases, Faculty of Applied Biological Sciences,Gifu University, 1-1 Yanagido, Gifu 501-1193,Japan
3. Laboratory of Veterinary Pathology, School of Veterinary Medicine,Azabu University, 1-17-71 Fuchinobe, Kanagawa, 252-5201,Japan
4. Dairy Hygiene Research Division, National Institute of Animal Health,4 Hitsujigaoka, Hokkaido, 062-0045,Japan