1. Division of Health Sciences, Murdoch University, Murdoch, Western Australia 6150, Australia
2. Division of Parasitic Diseases, National Center for Infectious Diseases, Centers for Disease Control and Prevention, Public Health Service, U.S. Department of Health and Human Services, Atlanta, Georgia 30341
3. Pathology and Parasitology Department, State Veterinary Institute Prague, 165 03 Prague 6, Czech Republic