Author's Organization:Department of Veterinary Microbiology, Faculty of Agriculture, Miyazaki University Department of Veterinary Microbiology, Faculty of Agriculture, Miyazaki University Department of Veterinary Microbiology, Faculty of Agriculture, Miyazaki University Department of Veterinary Microbiology, Faculty of Agriculture, Miyazaki University Department of Veterinary Hygiene, Nippon Veterinary and Zootechnical College