1. The United Graduate School of Veterinary Sciences, Gifu University, 1–1 Yanagito, Gifu-shi, Gifu 501–1193, Japan
2. Research and Education Center for Prevention of Global Infectious Diseases of Animals, Tokyo University of Agriculture and Technology, 3–5–8 Saiwai-cho, Fuchu, Tokyo 183–0054, Japan
3. Department of Applied Aquabiology, National Fisheries University, 2–7–1, Nagata-Honmachi, Shimonoseki, Yamaguchi 759–6595, Japan
4. Graduate School of Agriculture, Tokyo University of Agriculture and Technology, 3–5–8 Saiwai-cho, Fuchu, Tokyo 183–0054, Japan
5. School of Marine Science and Technology, Tokai University, 3–20–1 Orido, Shimizu-ku, Shizuoka 424–0902, Japan