1. Section of Bacteriology, National Veterinary Institute, P.O. Box 8156 Dep, N-0033 Oslo, Norway
2. Section of Wildlife Diseases, National Veterinary Institute, P.O. Box 8156 Dep, N-0033 Oslo, Norway
3. Division of Infectious Disease Control, Norwegian Institute of Public Health, N-0403 Oslo, Norway
4. Department of Pharmacology, Microbiology and Food Hygiene, The Norwegian School of Veterinary Science, Box 8146 Dep, 0033 Oslo, Norway