1. Department of Clinical Studies, University of Pennsylvania, School of Veterinary Medicine, Philadelphia, PA, USA
2. Current address: Mount Laurel Animal Hospital, Mount Laurel, NJ, USA
3. Current address: New England Animal Medical Center, West Bridgewater, MA, USA
4. Department of Anatomic Pathobiology, University of Pennsylvania, School of Veterinary Medicine, Philadelphia, PA, USA
5. Current address: Antech Diagnostics, Irvine, CA, USA