1. Graduate School of Animal and Food Hygiene, Obihiro University of Agriculture and Veterinary Medicine, Obihiro 080-8555, Japan
2. Center for Molecular Medicine, Jichi Medical University, Shimotsuke, Tochigi 349-0498, Japan
3. Department of Clinical Veterinary Science, Obihiro University of Agriculture and Veterinary Medicine, Obihiro 080-8555, Japan