1. Department of Molecular Microbiology, Washington University School of Medicine, 660 S. Euclid Ave., St. Louis, Missouri 63110
2. Department of Pathobiology, College of Veterinary Medicine, University of Illinois at Urbana-Champaign, 2001 S. Lincoln Ave., Urbana, Illinois 61801
3. Animal Parasitic Diseases Lab, BARC-East, Bldg. 1001, ANRI, Agricultural Research Service, USDA, Beltsville, Maryland 20705