1. Department of Veterinary Clinical Medicine, College of Veterinary Medicine, University of Illinois, Urbana, IL
2. Department of Clinical Sciences, College of Veterinary Medicine, Kansas State University, Manhattan, KS
3. Department of Veterinary Clinical Sciences, College of Veterinary Medicine, University of Minnesota, St Paul, MN
4. Department of Medicine and Epidemiology, School of Veterinary Medicine, University of California-Davis, Davis, CA