1. From the University of California, Davis; William Pritchard Veterinary Medical Teaching Hospital; School of Veterinary Medicine; University of California; Davis; CA 95616-8747
2. Department of Surgical and Radiological Sciences; School of Veterinary Medicine; University of California; Davis; CA 95616-8747
3. Department of Pathology; Microbiology, and Immunology; School of Veterinary Medicine; University of California; Davis; CA 95616-8747
4. Department of Clinical Sciences; College of Veterinary Medicine; Cornell University; Ithaca; NY 14853-6401