1. Department of Microbiology, Infectious and Parasitic Diseases, Faculty of Veterinary Medicine, Trakia University, Stara Zagora, Bulgaria.
2. Department of Infectious Diseases, IDEXX Laboratories, Ludwigsburg, Germany.
3. Department of General and Clinical Pathology, Faculty of Veterinary Medicine, Trakia University, Stara Zagora, Bulgaria.
4. Department of Infectious Diseases, Military Medical Academy, Sofia, Bulgaria.