1. Laboratory of Zoonotic Diseases, School of Veterinary Medicine, Rakuno Gakuen University, 582 Bunkyodai-Midorimachi, Ebetsu, Hokkaido 069-8501, Japan
2. Department of Virology, Institute of Tropical Medicine, Nagasaki University, 1-12-4 Sakamoto, Nagasaki, Nagasaki 852-8523, Japan
3. National Research Center for the Control and Prevention of Infectious Diseases, Nagasaki University, 1-14 Bunkyomachi, Nagasaki, Nagasaki 852-8521, Japan
4. Laboratory of Veterinary Virology, School of Veterinary Medicine, Rakuno Gakuen University, 582 Bunkyodai-Midorimachi, Ebetsu, Hokkaido 069-8501, Japan