A total of 395 adult ixodid ticks from three genera (Dermacentor, Haemaphysalis, and Ixodes) collected from the Urals to the Far East of Russia were tested by PCR and sequencing for the presence of spotted fever rickettsiae, anaplasmae, and ehrlichiae. Four, pathogens recognized in humans were detected in ticks: Rickettsia sibirica, R. heilongjiangensis, R. helvetica, and Anaplasma phagocytophilum. In addition, rickettsiae and ehrlichiae of unknown pathogenicity were detected, including Rickettsia sp. RpA4, Rickettsia sp. DnS14, Rickettsia sp. DnS28, "Candidatus R. tarasevichiae," a rickettsia closely related to R. helvetica, A. bovis, Ehrlichia muris, "Ehrlichia-like" "Schotti variant," and bacterium "Montezuma." Our findings indicated the distribution of rickettsiae and ehrlichiae in hard ticks in Russia.

We collected 209 Ixodes persulcatus ticks in various regions of Russia, including the southern Urals and western and eastern Siberia. Using PCR amplification and sequencing of the citrate synthase-encoding gene (gltA), we detected a new rickettsial genotype, which we named "Candidatus Rickettsia tarasevichiae." This bacterium was found in 9.27%, 10.0%, and 20.5% of the ticks collected in western Siberia, eastern Siberia, and the southern Urals, respectively. "Candidatus Rickettsia tarasevichiae" exhibited a 98% and 96% nucleotide sequence homology, with the 16S rDNA and gltA sequence, respectively, of R. canadensis, a rickettsia previously only found in Haemaphysalis leporispalustris ticks in North America. The phylogenetic analysis of "Candidatus Rickettsia tarasevichiae" and other Rickettsia species allowed the creation of a new cluster with high bootstrap values within the Rickettsia genus involving this rickettsia, R. canadensis, and three uncultured rickettsiae from plant insects.

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Thirty-one rickettsial isolates from ticks or patients in North Asian tick typhus (NATT) foci from the Ural region to the Russian Far East were obtained at the Omsk Research Institute of Natural Foci Infections between 1954 and 2001. Using citrate synthase (gltA) and outermenbrane protein a (ompA) gene sequencing, we identified these isolates as Rickettsia sibirica sensu stricto (25 isolates), R. sibirica strain BJ-90 (2 isolates), R. slovaca (1 isolate), and R. heilongjiangensis (3 isolates). We demonstrate that Ixodes persulcatus ticks should be considered potential vectors of NATT. We also demonstrate the presence of R. slovaca in Ural and R. heilongjiangensis in Siberia and Russian Far East, where they may cause human infections misdiagnosed as cases of NATT. Clinicians should be aware that several spotted fever rickettsioses with different prognoses coexist in Russia in areas where NATT was the only previously recognized rickettsiosis.

Using PCR, we screened 411 ticks from four genera collected in Russia and Kazakhstan for the presence of rickettsiae and ehrlichiae. In Russia, we detected "Rickettsia heilongjiangensis," Rickettsia sp. strain RpA4, and Ehrlichia muris. In Kazakhstan, we detected Rickettsia sp. strain RpA4 and a rickettsia closely related to Rickettsia aeschlimannii. These agents should be considered in a differential diagnosis of tick-borne infections in these areas.