Detection of Genetic Markers of Rickettsioses Agents of the Tick-Borne Spotted Fever Group in Certain Districts of the Saratov Region

In the Russian Federation, human cases of the tick-borne spotted fever group (SFG) rickettsioses are reported annually, and endemic foci of SFG rickettsioses exist, including Siberian tick typhus, Astrakhan spotted fever and Mediterranean (Marseilles) fever, which highlights the epidemiological significance of these infections. The Saratov Region is an endemic one for several natural-focal diseases (Ixodidae tick-borne borreliosis, West Nile fever, etc.) and demonstrates climatic and landscape-geographical conditions favorable for the spread of tick-borne pathogens. However, until now, no data were available on the circulation of SFG rickettsiosis in this region.
The aim of the work was to detect genetic markers of pathogens of tick-borne spotted fever group rickettsioses in tick samples collected during epizootiological monitoring of natural focal infections in the Saratov Region between 2021 and 2024.
Materials and methods. For this study, 4582 specimens of Ixodidae ticks and gamaside mites belonging to 14 species were collected from 10 districts of the Saratov Region and municipal settlement “Saratov city”, pooled into 1055 samples. PCR was used to detect genetic markers of Rickettsia spp. SFG and Rickettsia conorii.
Results and discussion. Genetic markers of SFG rickettsioses have been detected for the first time in the Saratov Region. DNA of Rickettsia spp. SFG were identified in 262 (26 %) samples from 11 tick species, collected across all surveyed areas. DNA markers of R. conorii were found in 23 (2.3 %) pooled samples from two tick species, obtained from three districts of the region and the Saratov municipality. These findings suggest the potential circulation of SFG rickettsioses in the Saratov Region and emphasize the need for further studies of the distribution, diversity and vector associations of pathogenic Rickettsia species in the region.

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