1. Department of Veterinary Pathobiology, College of Veterinary Medicine and Biomedical Sciences, Texas A&M University, College Station, TX 77843, U.S.A.
2. Department of Small Animal Clinical Sciences, College of Veterinary Medicine and Biomedical Sciences, Texas A&M University, College Station, TX 77843, U.S.A.
3. Department of Diagnostic Medicine/Pathobiology, College of Veterinary Medicine, Kansas State University, Manhattan, KS 66506-5802, U.S.A.
4. Veterinary Histology and Pathology, Institute for Animal Health, Veterinary College, University of Las Palmas de Gran Canaria, Trasmontaña s/n, Arucas 35413, Gran Canaria, Spain