1. Yamagata Prefectural Syonai Livestock Hygiene Division, Mikawa, Yamagata, Japan
2. Graduate School of Life and Environmental Sciences, Tsukuba University, Tsukuba, Ibaraki, Japan
3. National Institute of Livestock and Grassland Science, NARO, Tsukuba, Ibaraki, Japan
4. DKK-TOA Yamagata Corporation, Shinjo, Yamagata, Japan
5. Cooperative Department of Veterinary Medicine, Faculty of Agriculture, Iwate University, Morioka, Iwate, Japan