1. Institute of Parasitology and Zoology; University of Berne; Länggass-Strasse 122 CH-3001 Berne Switzerland
2. Institute of Parasitology; University of Berne; Länggass-Strasse 122 CH-3001 Berne Switzerland
3. Clinical Virology Group; Institute of Virology; University of Veterinary Medicine; Vienna, Veterinärplatz 1 A- 1210 Vienna Austria
4. Veterinary Practice; Bahnhofstrasse 27 A-4150 Rohrbach Austria