1. Department of Communicable Disease Control, Västra Götaland, Sweden.
2. Department of Communicable Disease Control, Halland, Sweden.
3. Environmental Administration Office, Göteborg, Sweden.
4. Bacteriology Laboratory, Sahlgrens University Hospital, Göteborg, Sweden.
5. Swedish Institute for Infectious Disease Control, Stockholm, Sweden.
6. National Veterinary Institute, Uppsala, Sweden.
7. Swedish Board of Agriculture, Jönköping, Sweden.
8. Environmental Administration Office, Varberg, Sweden.