1. 1Miyagi Prefectural Institute of Public Health and Environment, 4-7-2 Saiwai-cho Miyagino-ku, Sendai-shi 983-0836
2. 2Department of Biomedical Food Research, National Institute of Infectious Diseases, 1-23-1, Toyama, Shinjuku-ku, Tokyo, 162-8640
3. 3Department of Veterinary Microbiology, Faculty of Agriculture, Iwate University, 3-18-8 Ueda, Morioka, Iwate 020-0066, Japan