1. Department of Parasitology; National Institute of Infectious Diseases; Toyama 1-23-1, Shinjuku Tokyo 162-8640 Japan
2. National Research Centre for Protozoan Diseases; Obihiro University of Agriculture and Veterinary Medicine; Hokkaido 080-8555 Japan
3. Department of Parasitology; Nippon Veterinary and Life Science University; Sakaiminami 1-7-1, Musashino Tokyo 180-8602 Japan