1. California Regional Primate Research Center,1
2. Department of Veterinary Pathology, Microbiology and Immunology,2 and
3. Center for Comparative Medicine,3 School of Veterinary Medicine, University of California, Davis, California 95616;
4. Bayer Reference Laboratory, Emeryville, California 946084; and
5. Department of Infectious Diseases, Northwestern University School of Medicine, Chicago, Illinois 606115