1. 1Zoological Institute, Braunschweig University of Technology, 38106 Braunschweig, Germany
2. 2Friedrich-Loeffler-Institute, Institute of Animal Welfare and Animal Husbandry, 29223 Celle, Germany
3. 3Department of Pathology, Bacteriology and Avian Diseases, Faculty of Veterinary Medicine, Ghent University, 9820 Merelbeke, Belgium