1. Laboratory of Veterinary Microbiology, Faculty of Agriculture, Yamaguchi University, 1677-1 Yoshida, Yamaguchi 753-8515, Japan
2. Laboratory of System Physiology, Faculty of Agriculture, Yamaguchi University, 1677-1 Yoshida, Yamaguchi 753-8515, Japan
3. Laboratory of Veterinary Pathology, Azabu University, 1-17-71 Fuchinobe, Kanagawa 252-5201, Japan
4. Akiyoshidai Safari Land, 1212 Aka, Mito, Mine, Yamaguchi 754-0302, Japan