1. Center for Infectious Disease Epidemiology and Prevention Research, Tokyo University of Agriculture and Technology, Fuchu, Tokyo 183-8509, Japan
2. School of Veterinary Medicine, Azabu University, Sagamihara, Kanagawa 252-5201, Japan
3. Department of Microbiology and Infection Control, Faculty of Medicine, Osaka Medical and Pharmaceutical University, Osaka 569-8686, Japan
4. Ishikawa Nanbu Livestock Hygiene Service Center, Kanazawa, Ishikawa 920–3101, Japan
5. Faculty of Veterinary Science, Nippon Veterinary and Life Science University, Musashino, Tokyo 180-8602, Japan