1. Department of Small Animal Clinical Sciences, College of Veterinary Medicine, Veterinary Medical Teaching Hospital, Box 100126, Health Science Center, Gainesville, Florida 32610-0126, USA
2. Author for reprint requests
3. Department of Pathobiology, College of Veterinary Medicine, Veterinary Medical Teaching Hospital, Box 100103, Health Science Center, Gainesville, Florida 32610-0103, USA
4. Present address: Texas Veterinary Medicine Diagnostic Laboratory, PO Drawer 3040, College Station, Texas 77841, USA