1. Department of Applied Veterinary Sciences, United Graduate School of Veterinary Sciences, Gifu University, 1–1 Yanagido, Gifu 501–1193, Japan
2. Laboratory of Veterinary Virology, Department of Pathobiology, School of Veterinary Medicine, Rakuno Gakuen University, 582 Bunkyoudai Midori-machi, Ebetsu, Hokkaido 069–8501, Japan
3. Laboratory of Veterinary Microbiology, Faculty of Applied Biological Sciences, Gifu University, 1–1 Yanagido, Gifu 501–1193, Japan
4. Laboratory of Comparative Pathology, Graduate School of Veterinary Medicine, Hokkaido University, West 9 North 18, Kita-ku, Sapporo 060-0818, Japan
5. Research and Education Center for Prevention of Global Infectious Disease of Animal, Tokyo University of Agriculture and Technology, Fuchu, Tokyo 183-8509, Japan