1. Department of Infectious Diseases of Animals and Bees, Faculty of Veterinary Medicine, University of Belgrade, Bulevar Oslobodjanja 18, 11000 Belgrade, Serbia
2. Institute of Microbiology, Military Medical Academy, Crvotravska 17, 11000 Belgrade, Serbia
3. Institute of Epidemiology, Military Medical Academy, Crnotravska 17, 11000 Belgrade, Serbia
4. Instutute for Medical Research, University of Belgrade, Dr Subotića 4, 11129 Belgrade 102, Serbia.