1. Department of Infectious Diseases; Tokai University School of Medicine; Isehara Kanagawa 259-1193 Japan
2. Department of Immunogenetics; Institute of Tropical Medicine; Nagasaki University; Nagasaki 852-8523 Japan
3. Department of Veterinary Pathobiology; Faculty of Veterinary Medicine and Animal Science; University of Peradeniya; Peradeniya Sri Lanka
4. Department of Tropical Medicine and Parasitology; Keio University School of Medicine; Tokyo 160-8582 Japan