Authors
Georgi G. Zhelev
Department of Epidemiology, Infectious Diseases and Preventive Medicine, Faculty of Veterinary Medicine, Trakian University, Stara Zagora, Bulgaria
Kojcho P. Koev
Department of Epidemiology, Infectious Diseases and Preventive Medicine, Faculty of Veterinary Medicine, Trakian University, Stara Zagora, Bulgaria
Vladimir D. Dimitrov
Varna, Bulgaria
Vladimir S. Petrov
Department of Epidemiology, Infectious Diseases and Preventive Medicine, Faculty of Veterinary Medicine, Trakian University, Stara Zagora, Bulgaria