1. Department of Pathological and Preventive Veterinary Science, The United Graduate School of Veterinary Science, Yamaguchi University, 1677–1 Yoshida, Yamaguchi 753–8511, Japan
2. Laboratory of Veterinary Parasitology, School of Veterinary Medicine, Faculty of Agriculture, Tottori University, 4–101 Koyama-Minami, Tottori 680–8553, Japan
3. Department of Microbiology, Osaka City Institute of Public Health and Environmental Sciences, 8–34 Tojo-cho, Tennoji-ku, Osaka 543–0026, Japan