Introduction: In recent years, there has been growing interest in tick-borne infections, particularly tick-borne rickettsioses (TBRs). Assessing the genospecies composition and regional distribution of spotted fever group rickettsiae (SFGR) is crucial for optimizing risk-based surveillance of TBR. However, the genospecies diversity of SFGR populations in the Russian Federation remains understudied. To address this, we studied ticks collected from vegetation, humans, and animals in eight regions of Russia to identify the SFGR genospecies, which may have significance for human morbidity.
Materials and Methods: From 2020 to 2024, we collected 2,431 ticks from eight regions of Russia, representing Western Siberia (Altai Krai), North Caucasus (Karachay-Cherkessia), Southern Russia (Astrakhan Oblast), the Volga region (Samara Oblast), Central Russia (Moscow, Tula Oblast, Oryol Oblast), and Central Europe (Kaliningrad Oblast). We utilized commercial qPCR kits for SFGR screening and identified genospecies by Sanger sequencing partial genes for citrate synthase (gltA) and outer-membrane protein A (ompA), comparing the results with the GenBank database.
Results: Our findings revealed six distinct genospecies of SFGR across the eight regions of Russia; however, the diversity of these genospecies varied by region. The highest diversity (five genospecies: R. raoultii, R. slovaca, R. helvetica, R. monacensis, and R. aeschlimannii) was found in North Caucasus in ticks from three genera. In Western Siberia, we detected three genospecies—R. sibirica, R. raoultii, and R. helvetica—in two genera of ticks. In the Volga region, the genospecies R. slovaca and R. raoultii were found in Dermacentor ticks, while in Southern Russia, R. raoultii and R. aeschlimannii were identified in two different genera of ticks. Central Russia (three regions) and Europe showed a similar pattern, with R. raoultii in Dermacentor and R. helvetica in Ixodes.
Conclusions: Our study highlights significant regional variations in SFGR genospecies diversity in Russia, underscoring the necessity for ongoing research and monitoring for public health.
