1. Veterinary Public Health Institute; University of Berne; Liebefeld Switzerland
2. Federal Veterinary Office; Liebefeld Switzerland
3. Qualiporc Genossenschaft; Oberriet Switzerland
4. Institute for Virology and Immunology; Mittelhäusern Switzerland
5. Clinic for Swine; University of Berne; Berne Switzerland
6. Institute of Virology; Department of Infectious Diseases; University of Veterinary Medicine Hannover; Hannover Germany
7. Clinic for Swine; Ludwig-Maximilians-University Munich; Oberschleissheim Germany
8. Swine Health Service Baden-Wuerttemberg; Aulendorf Germany