1. Department of Clinical Research and Veterinary Public Health; Vetsuisse Faculty; University of Berne; Länggass-Strasse 124 Berne 3012 Switzerland
2. Department of Zoonoses; Faculty of Veterinary Medicine; Cairo University; PO Box 12211 Giza Egypt
3. Institute for Experimental Pathology; Biomedical Center; University of Iceland; Keldur, Keldnavegur 3 Reykjavik 112 Iceland
4. Swiss Institute of Allergy and Asthma Research (SIAF); Obere Strasse 22 Davos 7270 Switzerland
5. Department of Population Medicine and Diagnostic Sciences; College of Veterinary Medicine; Cornell University; Ithaca NY 14853 USA