1. Department of Applied Veterinary Sciences, United Graduate School of Veterinary Sciences, Gifu University, 1-1 Yanagido, Gifu 501-1193, Japan
2. Eaglet Office Inc., 348-1 Shimoitanami, Maibara-shi, Shiga 521-0306, Japan
3. Center for Infectious Diseases Epidemiology and Prevention Research, Tokyo University of Agriculture and Technology, 3-5-8 Saiwai-cho, Fuchu-shi, Tokyo 183-8509, Japan