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We collected 209 Ixodes persulcatusticks 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 leporispalustristicks in North America. The phylogenetic analysis of 'Candidatus Rickettsia tarasevichiae' and other Rickettsiaspecies allowed the creation of a new cluster with high bootstrap values within the Rickettsiagenus involving this rickettsia, R. canadensis, and three uncultured rickettsiae from plant insects.

North Asian tick-typhus (NATT), also known as Siberian tick typhus, is the main tick-borne rickettsiosis in Siberia, Russia. Recently, a fatal infection in a four-year-old girl with typical tick-borne rickettsiosis symptoms (fever, rash, eschar at the site of the tick bite, myalgia) and meningeal syndrome was registered. In order to identify the etiology of this infection, blood and brain samples from the patient were examined for the presence of a wide range of tick-transmitted agents and enteric viruses by polymerase chain reaction with subsequent sequencing. Rickettsia sibiricasubsp. sibiricaand “CandidatusRickettsia tarasevichiae” DNA was identified in both blood and brain samples. Rickettsia sibiricawas characterized by the gltA, ompAand ompBgenes, and “CandidatusR. tarasevichiae” was characterized by the gltAand ompBgenes. We report the first case of mixed R. sibiricaand “CandidatusR. tarasevichiae” human infection with a fatal outcome in Russia.

ABSTRACTUsing 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,” Rickettsiasp. strain RpA4, and Ehrlichia muris. In Kazakhstan, we detected Rickettsiasp. 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.