1. From the Department of Clinical Sciences, Carlson College of Veterinary Medicine, Oregon State University, Corvallis, Oregon (K.H.).
2. From the Department of Biomedical Sciences and Pathobiology (T.L.), Virginia-Maryland College of Veterinary Medicine, Blacksburg, Virginia.
3. From the Department of Small Animal Clinical Sciences (B.P.), Virginia-Maryland College of Veterinary Medicine, Blacksburg, Virginia.
4. From the Department of Small Animal Clinical Sciences, Virginia Tech, Blacksburg, Virginia (N.D.)