1. Department of Veterinary Pathobiology, University of Illinois, 2001 S. Lincoln Ave., Urbana, IL 61802
2. Departments of Pathology, Microbiology and Immunology, School of Veterinary Medicine, University of California, Davis, CA 95616
3. Departments of Medicine and Epidemiology, School of Veterinary Medicine, University of California, Davis, CA 95616