1. Department of Medicine & Epidemiology, School of Veterinary Medicine, University of California, Davis, CA 95616, USA, and Davis Dermatology Group, School of Veterinary Medicine, University of California, Davis, CA 95616, USA
2. Department of Anatomy, Physiological Sciences and Radiology, College of Veterinary Medicine, North Carolina State University, 4700 Hillsborough Street, Raleigh, North Carolina 27606, USA
3. Davis Dermatology Group, School of Veterinary Medicine, University of California, Davis, CA 95616, USA, and Animal Allergy & Skin Clinic, 4100 SW. 109th Avenue, Beaverton, Oregon 97005, USA