Sympatric Occurrence of Rickettsia slovaca and Rickettsia raoultii in Dermacentor Ticks from Samara Oblast and the First Molecular Detection of Rickettsia felis in Russia and Globally in Dermacentor reticulatus

Samara Oblast is an ecological transition zone in Russia, yet its spotted fever group Rickettsia (SFGR) diversity and prevalence in Dermacentor ticks remain unexplored. This study characterized SFGR species circulating in Dermacentor reticulatus and Dermacentor marginatus across 15 districts of Samara Oblast. We collected 681 adult Dermacentor ticks via vegetation flagging during 2023–2025. SFGR screening was performed via a commercial qPCR kit. Genospecies were identified via Sanger sequencing of the partial gltA gene and validated by means of ompB analysis, while tick species were confirmed using a cox1 gene fragment. The overall SFGR prevalence was 33.5% (228/681). Infection rates were significantly higher in D. marginatus (44.7%) than in D. reticulatus (27.5%). Rickettsia raoultii predominated (94.4%), while Rickettsia slovaca was relatively rare (4.6%) and significantly associated with D. marginatus. Notably, partial ompB sequencing revealed two distinct R. raoultii putative genotypes circulating in the region: one with a 9 bp deletion and one without. No coinfections were detected. Unexpectedly, a single D. reticulatus tick tested positive for Rickettsia felis, confirmed by means of gltA and ompB, marking the first molecular detection of R. felis in Russia and globally in this tick species. Samara Oblast represents a high-prevalence sympatric zone for Dermacentor-borne SFGR. The molecular detection of R. felis in D. reticulatus suggests a potential association that requires confirmation through further studies.