1. From the National Veterinary Institute, Department of Pathology, S-751 89, Uppsala, Sweden
2. Swedish National Board of Agriculture, Vallgatan 8, 551 82, Jönköping, Sweden
3. Institute for Zoo Biology and Wildlife Research Berlin, Alfred-Kowalke-Strasse 17, PO Box 1103, 10252, Berlin, Germany
4. Nåntuna backe, S-757 59, Uppsala, Sweden