1. Institute of Hygiene, University Hospital Münster, Münster, Germany
2. Department of Medical Microbiology, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands
3. Pig Health Services, Landwirtschaftskammer Niedersachsen, Meppen, Germany
4. Pig Health Services, Landwirtschaftskammer Nordrhein-Westfalen, Bonn, Germany