1. Department of Veterinary Public Health, Nippon Veterinary and Life Sciences University, Tokyo 180-8602, Japan
2. Kitasato-Otsuka, Biomedical Assay Laboratories Co., Ltd. Kanagawa 228-8555, Japan
3. First Department (Neurology) of Internal Medicine, School of Medicine, Kurume University, Fukuoka 830-0011, Japan
4. Department of Veterinary Science, National Institute of Infectious Diseases, Tokyo 162-8640, Japan
5. Department of Biomedical Science, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Tokyo 113-8657, Japan