1. Department of Pathology, College of Veterinary Medicine, The University of Tennessee, Knoxville, TN 37996–4500, USA
2. Department of Small Animal Clinical Sciences, College of Veterinary Medicine, The University of Tennessee, Knoxville, TN 37996–4500, USA
3. Department of Small Animal Clinical Sciences, College of Veterinary Medicine, The University of Tennessee, Knoxville, TN 37996–4500, USA, and Rowley Memorial Animal Hospital, 171 Union Street, Springfield, MA 01105, USA