1. Department of Clinical Veterinary Science, Obihiro University of Agriculture and Veterinary Medicine, Obihiro 080–8555, Japan
2. Department of Basic Veterinary Science, Obihiro University of Agriculture and Veterinary Medicine, Obihiro 080–8555, Japan
3. National Research Center for Protozoan Diseases, Obihiro University of Agriculture and Veterinary Medicine, Obihiro, Hokkaido 080–8555, Japan