1. Department of Biometry, Epidemiology and Information Processing, WHO Collaborating Centre for Research and Training for Health at the Human-Animal-Environment Interface, University of Veterinary Medicine Hannover, 30559 Hanover, Germany
2. Lower Saxonian Animal Diseases Fund, 30169 Hanover, Germany
3. Animal Health Service, Thuringian Animal Diseases Fund, 07745 Jena, Germany