1. Departments of Medical Microbiology & Infectious Diseases1 and
2. Neurology and Immunology,2 Erasmus University Medical Center Rotterdam, Rotterdam, and
3. DLO-Institute for Animal Science and Health, Lelystad,3 The Netherlands, and
4. National Laboratory for Enteric Pathogens, Canadian Science Centre for Human and Animal Health, LCDC, Winnipeg, Canada4