1. National Research Center for Protozoan Diseases, Obihiro University of Agriculture and Veterinary Medicine, Inada-cho, Obihiro, Hokkaido 080–8555, Japan
2. Department of Protozoology, Institute of Tropical Medicine (NEKKEN), Nagasaki University, 1–12–4 Sakamoto, Nagasaki 852–8523, Japan
3. Laboratory of Veterinary Parasitology, Faculty of Agriculture, Iwate University, 3–18–8 Ueda, Morioka, Iwate 020–8550, Japan