Distribution of the causative agent of relapsing tick-borne fever Borrelia miyamotoi in natural foci in the Tomsk region

Abstract

Background: Knowledge about the infectious potential of the causative agent of recurrent tick-borne fever Borrelia miyamotoi and the role of this pathogen in the etiological structure formation of transmissible natural focal infections in a number of regions remains incomplete. Among them is the Tomsk region where in 2021 the incidence of ixodic tick-borne borreliosis was 15.7 per 100 thousand population, which is 3.6 times higher than the all-Russian indicator.
 Aims: to summarize and analyze epidemiological data, as well as the results of our own clinical observations and laboratory studies conducted in 2015-2021 confirming the distribution of the causative agent of relapsing tick-borne fever B. miyamotoi in the Tomsk region.
 Materials and methods: Epidemiological data on the manifestation of natural foci of tick-borne infections were analyzed in the Tomsk region for the period 2015-2021. A clinical case of febrile infection caused by B. miyamotoi infection is described as an example of underdiagnosis of relapsing tick-borne fever. Verification of the etiological variant of borreliosis was carried out using real-time PCR. DNA extraction and detection of B. miyamotoi genetic markers were performed using RealBest series kits (Vector-Best, Novosibirsk), followed by nucleic acid sequencing of B. miyamotoi 23SrRNA, glpQ, and recA gene sequences.
 Ixodid ticks (I. persulcatus, I. pavlovskyi, D. reticulatus) collected in the Tomsk region were studied for infestation with B. miyamotoi. Detection of genetic markers of pathogenic borrelia was carried out in nucleic acid samples isolated from tick homogenates using kits of the RealBest series (Vector-Best, Novosibirsk).
 Results: In 2016, the first clinical case of borreliosis caused by B. miyamotoi confirmed by molecular genetic methods in the Tomsk region was identified. During the period 2015-2021, the infection rate of B. miyamotoi ticks of the genus Ixodes in the Tomsk region was up to 7%; ticks of the genus Dermacentor up to 3%.
 Conclusion. The results of this study demonstrated the distribution the causative agent of relapsing tick-borne fever B. miyamotoi in the natural foci of the Tomsk region, which requires further monitoring of the epizootic situation and study of the role of this pathogen in the formation of the etiological structure of transmission natural focal infections.