1. Departments of Infectious Diseases and
2. Molecular Biology, Umeå University, SE-9018 Umeå, Sweden
3. Research Institute for Zoonotic Ecology and Epidemiology, Olands Skogsby 6280, SE-386 93 Färjestaden, Sweden
4. Department of Animal Ecology, Ecology Building, Lund University, SE-223 62 Lund, Sweden
5. Department of Zoology, University of Göteborg, Box 463, SE-405 30 Göteborg, Sweden
6. Department of Bacteriology, National Veterinary Institute, SE-751 89 Uppsala, Sweden