1. Yamagata Integrated Agricultural Research Center Swine Experiment Station, 1 Hamanaka, Yamagata 998–0112, Japan
2. Yamagata Shonai Livestock Hygiene Service Center, 139 Yokoyama, Yamagata 997–1301, Japan
3. Yamagata Mogami Livestock Hygiene Service Center, 2034 Kanazawa, Yamagata 996–0002, Japan