Introduction. To improve the epidemiological surveillance of brucellosis in Russia, a detailed analysis of incidence and characteristics of Brucella melitensis strains circulating in the territories ...of the country where there is a persistent epizootic and epidemiological problem with brucellosis is required.Purpose of the study. To study current trends in the brucellosis epidemic process and perform molecular analysis of Brucella isolates from the territories of Southern and North Caucasian Federal Districts with long lasting unfavorable situation with brucellosis — the Republics of Dagestan (RD), Kalmykia (RK) and Stavropol Krai (SK).Materials and methods. The analysis of the brucellosis incidence in the North Caucasus Federal District and the Southern Federal District was carried out on the basis of data from the Rospotrebnadzor Departments for the period 2011–2020. Total 56 cultures of Brucella melitensis, isolated in 1999–2019 from patients with brucellosis that permanently resided in RD, RK and SK were studied.Results. The key factor contributing to the epidemic manifestations of brucellosis in the south of the European part of Russia is the persistence of epizootic foci in cattle and small ruminants. The leading concomitant factors are as follows: the presence in the region of "hidden" epizootic foci, uncontrolled production of food products of animal husbandry and its illegal sale to customers, unauthorized movement of animals and livestock products, untimely delivery (concealment) of sick cattle for stamping out. Results of molecular analysis of B. melitensis strains indicate the circulation of a mixed population of brucella, which is generally characteristic of the entire region, without a pronounced confinement of isolates to separate administrative territories. At the same time, the entire studied sample of strains can be divided into two groups (72% and 28% of strains) based on MLVA-16 genotypes by the variability in the Bruce 19 locus, which makes it possible to associate a part of the studied strains with the territory of their isolation.Discussion. The data obtained make it possible to scientifically substantiate the possibility of considering the affected territories of the Southern Federal District and the North Caucasian Federal District as a single common persistent active anthropurgic epizootic focus with circulation of a mixed, but typical for the region population of Brucella strains.
