1. Department of Disease Control, Graduate School of Veterinary Medicine, Hokkaido University, Sapporo 060-0818, Japan.
2. Present Address: Laboratory of Veterinary Microbiology, Faculty of Applied Biological Sciences, Gifu University, Gifu 501-1193, Japan.
3. Hokkaido Green-Bio Institute, Yubari-gun 069-1311, Japan.
4. Research Institute of Biological Resources, National Institute of Advanced Industrial and Science Technology, Sapporo 062-8517, Japan.
5. National Research Center for Protozoan Diseases, Obihiro University of Agriculture and Veterinary Medicine, Obihiro 080-8555, Japan.