1. Department of Histology and Pathology; Veterinary Faculty; ULPGC; Trasmontañia s/n 35416 Arucas (Las Palmas) Spain
2. Department of Infectious Diseases; Veterinary Faculty; ULPGC; Trasmontañia s/n 35416 Arucas (Las Palmas) Spain
3. Department of Pathobiology; College of Veterinary Medicine; University of Florida; PO Box 110880 Gainesville FL 36610 USA
4. Department of Pharmacology and Pathobiology; Royal Veterinary and Agricultural University; 13 Bülowsvej DK-1870 Frederiksberg C Copenhagen Denmark