Comprehensive Study of the Circulation of Spotted Fever Group Rickettsioses Pathogens in Certain Districts of the Saratov Region in 2025

Tick-borne rickettsioses are one of the leading causes of vector-borne infections in the Russian Federation. In Saratov Region, during 2021–2024, genetic markers of spotted fever group (SFG) rickettsiosis pathogens, identified as Rickettsia raoultii, R. conorii and R. slovaca, were detected in 8 species of Ixodidae ticks and 3 species of gamaside mites. A serological survey of the population in Engels region in 2024 revealed IgG antibodies to R. conorii in 6.4 % of samples; however, no SFG rickettsiosis foci or human cases have been officially registered in the region.
The aim of this study was to detect genetic markers in ticks and examine the population for the presence of specific antibodies to the causative agents of SFG rickettsioses in certain districts of the Saratov Region in 2025.
Materials and methods. A total of 1,411 specimens of hard and soft ticks and mites collected in 9 districts and the Saratov municipality were tested using PCR. Additionally, the ELISA method was applied to examine 400 blood sera from the residents.
Results and discussion. The presence of Rickettsia spp. SFG DNA was confirmed in tick suspension samples of 6 tick species. Ticks were collected in 8 districts and in the Saratov municipality. Genetic markers of R. conorii were identified in 2 tick species. Laboratory testing of serum samples for the presence of antibodies to R. conorii revealed the following: 46 samples containing IgG immunoglobulins and 2 samples containing IgM antibodies. The results obtained indicate the circulation of pathogenic rickettsiae in the Saratov Region and the possible existence of natural foci of SFG rickettsioses, which necessitates the inclusion of this group of infections in the epidemiological surveillance system.

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