Review of domestic and foreign scientific literature on brucella ecology, brucellosis epizootology and pathogenesis is presented. It has been found that the main route of transmitting the infection causative agents is vertical. At the same time the newborns receive such a small dose of brucella that for a long time it is impossible to confirm them being infected by the conventional diagnostic methods. The deterioration of the epizootic situation is explained precisely by the following – young cattle bred from sick cows are integrated in the broodstock. In this case many of them remain hidden carriers of the pathogen and do not respond to diagnostic tests (a state of tolerance). Young cattle infected with brucella are detected only after they become an active source of infection causing epizootic danger during 2–4 years, i.e. before calving or abortion, still remaining the undetected source of the pathogen. At the same time the conventional diagnostic methods are practically ineffective. In this case the diagnostic method based on the immunological tolerance phenomenon implying the use of the vaccine from the strain B. abortus 19 is applied, this is a serological test to detect the negatively responsive to brucellosis heifers that are 15–20 days after vaccination and to bar them from herd reproduction. In addition, when diagnosing brucellosis, it is necessary to take into account the latent course of the disease in adult animals. It is possible to reveal hidden carriers of brucella by provoking latent infection through immunisation with vaccines from the R-strains B. abortus 1096 or RV-51, which ensures the pathogen devastation.