BackgroundBrucellosis is a bacterial zoonotic disease. Annually in the world more than 500,000 new cases of brucellosis in humans are registered. In this study, we propose an evolutionary model of the historical distribution of B. melitensis based on the full-genomic SNP analysis of 98 strains.ResultsWe performed an analysis of the SNP of the complete genomes of 98 B. melitensis strains isolated in different geographical regions of the world to obtain relevant information on the population structure, genetic diversity and the evolution history of the species. Using genomic sequences of 21 strains of B. melitensis isolated in Russia and WGS data from the NCBI database, it was possible to identify five main genotypes and 13 species genotypes for analysis. Data analysis based on the Bayesian Phylogenetics and Phylogeography method allowed to determine the regions of geographical origin and the expected pathways of distribution of the main lines (genotypes and subgenotypes) of the pathogen.ConclusionsWithin the framework of our study, the model of global evolution and phylogeography of B. melitensis strains isolated in various regions of the planet was proposed for the first time. The sets of unique specific SNPs described in our study, for all identified genotypes and subgenotypes, can be used to develop new bacterial typing and identification systems for B. melitensis.Electronic supplementary materialThe online version of this article (10.1186/s12864-018-4762-2) contains supplementary material, which is available to authorized users.
An analysis of trends in the development of situation on brucellosis in the world over past decade and the data on the main risk factors for the occurrence of epidemiological complications regarding this infection in various regions of the world are provided in the paper. An expert assessment of the current epizootiological and epidemiological situation on brucellosis, the coverage of population and animals with immunization in the Russian Federation is given. Over 9 months of 2021, 210 potentially hazardous as regards brucellosis in cattle areas and 24 sites – as regards brucellosis in small ruminants – were registered in Russia. Compared to the same period in 2020, there was a decrease in the number of newly identified hazardous sites for bovine brucellosis by 35.8 % (117 areas). However, long-term upward trend in epizootiological adversity for bovine brucellosis in Russia persists. The epidemiological situation on brucellosis in the country for the period of 2012–2021 is characterized as unfavorable. Decrease in the number of newly detected human brucellosis cases (by 25.1 % of long-term average values) is observed against the background of persistent unfavorable epizootic conditions for brucellosis among epidemiologically significant species of small ruminants and cattle in regions with developed animal husbandry. In 2021, clusters of human cases were registered in the Republic of Dagestan and Penza Region. In the Republic of Dagestan, against the background of aggravation of epizootiological and epidemiological situation on brucellosis, there was also an alarming trend towards prevalence of a relatively high incidence among minors. The proportion of cases of brucellosis among children under the age of 17 in the Republic amounted to 60.3 % of the total number of minors with newly diagnosed brucellosis in Russia over the past 10 years. Taking into account current epizootic, epidemic situations and the long-term dynamics of the development of situation on brucellosis in the Russian Federation, the incidence of brucellosis among the population is predicted to be 10–15 % lower than the average long-term values – 0.18–0.20 per 100000 of the population – in 2022. The number of human cases of brucellosis can range from 250 to 300.
Analysis of brucellosis morbidity rates in humans and animals across the Russian Federation in 2017 is presented. Epidemic situation on the infection is characterized as unstable, the incidence and number of people with brucellosis are reduced in reference to the average long-term indicators by more than 20 %, against the background of epizootic situation aggravation as regards brucellosis of farm animals. There are cases of group outbreaks of brucellosis in the Stavropol Territory, Lipetsk and Penza Regions. According to the Federal Service for Veterinary and Phytosanitary Surveillance, analysis of the cumulative epizootic state of the population of epidemically significant species of cattle and small cattle in 2017 defines the risk of brucellosis in the Russian Federation as “high.” In 2018, the unstable epidemic situation on brucellosis will remain; there is high probability of outbreaks with cluster human incidence, including in the territory that is free from brucellosis. Predicted for 2018 morbidity rates on brucellosis in humans will be below the level of the average long-term morbidity and may be within the range of 330–360 cases.
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