1. Clinic of Small Animal Medicine, Ludwig-Maximilians-Universitaet of Munich; Veterinaerstrasse 13 Munich 80539 Germany
2. Institute for Animal Hygiene and Veterinary Public Health, University of Leipzig; An den Tierkliniken 1 Leipzig 04103 Germany
3. Department of Veterinary Sciences; Institute for Anatomy, Histology and Embryology, Ludwig-Maximilians-Universitaet of Munich; Veterinaerstrasse 13 Munich 80539 Germany