1. National Research Center for Protozoan Diseases, Obihiro University of Agriculture and Veterinary Medicine, 2-13 Inada, Obihiro, Hokkaido 080-8555, Japan.
2. Hokkaido Animal Research Center, Infectious Disease Section, Shintoku, Hokkaido 081-0038, Japan.
3. Research Center for Zoonosis Control, Hokkaido University, Sapporo 060-0818, Japan.