1. Faculty of Veterinary Medicine; Kasetsart University; Bangkok 10900 Thailand
2. Gunma Prefectural Institute of Public Health and Environmental Sciences; Maebashi Gunma 371-0052 Japan
3. National Institute of Health, Department of Medical Sciences; Ministry of Public Health; Nonthaburi 11000 Thailand
4. Faculty of Veterinary Medicine; Chiang Mai University; Chiang Mai 50100 Thailand
5. Department of Veterinary Medicine, College of Bioresource Science; Nihon University; Fujisawa Kanagawa 252-8510 Japan
6. National Institute of Health Sciences; Setagaya-ku Tokyo 158-8501 Japan
7. National Institute of Infectious Diseases, Infectious Disease Surveillance Center; Musashimurayama Tokyo 208-0011 Japan