1. National Research Center for Protozoan Diseases, Obihiro University of Agriculture and Veterinary Medicine, Obihiro, Hokkaido 080-8555, Japan
2. Department of Tropical Medicine and Parasitology, Dokkyo Medical University, Mibu, Tochigi 321-0293, Japan
3. Department of Parasitology, College of Public Health, University of the Philippines Manila, Philippines
4. Graduate School of Agricultural and Life Sciences, The University of Tokyo, Tokyo 113-8657, Japan