1. Shandong Vocational Animal Science and Veterinary College, 88, Shenglidong Street, Weifang 261061, China
2. Division of Infection Control and Disease Prevention, Graduate School of Agricultural and Life Sciences, The University of Tokyo, 1–1–1 Yayoi, Bunkyo-Ku, Tokyo 113–8657, Japan
3. Qinghai University and Tsinghua University Three Rivers Source Research Institute, Qinghai University, 25, Ningda Road, Xining 810016, China
4. Department of Veterinary Pathology, Graduate School of Agricultural and Life Sciences, The University of Tokyo, 1–1–1 Yayoi, Bunkyo-Ku, Tokyo 113–8657, Japan
5. Equine Research Institute, Japan Racing Association, 1400-4 Shiba, Shimotsuke, Tochigi 329-0412, Japan
6. Current address: Japan Farriery Association, JRA Shimbashi Bunkan Bldg., 4-5-4 Shimbashi, Minato-ku, Tokyo 105-0004, Japan