1. Biology Department, University of Southern Indiana, Evansville, Indiana 477121;
2. National Animal Disease Center, Agricultural Research Service, U.S. Department of Agriculture,2 and
3. Division of Infectious Diseases, West Los Angeles Veterans Affairs Medical Center, Los Angeles, California 900733;
4. Department of Pathology and Laboratory Medicine4 and
5. Department of Pathology, College of Veterinary Medicine, Iowa State University,5 Ames, Iowa 50010;
6. Department of Biomedical Research, Royal Tropical Institute, 1105 AZ Amsterdam, The Netherlands6
7. Department of Medicine,7 UCLA School of Medicine, Los Angeles, California 90095; and