1. Department of Equine and Small Animal Medicine Faculty of Veterinary Medicine, University of Helsinki P.O. Box 57 00014 Helsinki Finland
2. Department of Environmental and biological sciences University of Eastern Finland P.O. Box 111 80101 Joensuu Finland
3. Department of Basic Veterinary Sciences Faculty of Veterinary Medicine, University of Helsinki P.O. Box 66 00014 Helsinki Finland
4. Department of Veterinary Pathology Faculty of Veterinary Medicine, University of Helsinki P.O. Box 57 00014 Helsinki Finland