1. Department of Veterinary Pathology; Faculty of Veterinary Medicine; Freie Universität Berlin; Robert-von-Ostertag-Strasse 15 14163 Berlin Germany
2. Small Animal Clinic; Faculty of Veterinary Medicine; Freie Universität Berlin; Oertzenweng 19b 14163 Berlin Germany
3. Institute for Poultry Diseases; Faculty of Veterinary Medicine; Freie Universität Berlin; Königsweg 63 14163 Berlin Germany
4. Department of Anatomy, Histology and Embryology; Faculty of Veterinary Medicine; University of Leipzig; An den Tierkliniken 43 04103 Leipzig Germany
5. Institute for Virology; Faculty of Veterinary Medicine; University of Leipzig; An den Tierkliniken 29 04103 Leipzig Germany