1. Research and Education Center for Prevention of Global Infectious Diseases of Animals, Tokyo University of Agriculture and Technology, 3-5-8 Saiwai-cho, Fuchu-shi, Tokyo 183-8509, Japan
2. The United Graduate School of Veterinary Sciences, Gifu University, 1-1 Yanagito, Gifu-shi, Gifu 501-1193, Japan
3. Center for Infection and Immunity, Mailman School of Public Health, Columbia University, New York, NY 10032, U.S.A.
4. Laboratory of Epizootiology, Department of Veterinary Medicine Faculty and Agriculture, Tokyo University of Agriculture and Technology, Saiwai-cho, Fuchu-shi, Tokyo 183-8509, Japan