Fournier, Pierre‐Edouard

Abstract:  We recently reported the first documented cases of a new rickettsial disease caused by Rickettsia heilongjiangensis in the Russian Far East (Far Eastern tick‐borne rickettsiosis). Here we report the amplification of DNA of R. heilongjiangensis from both the skin biopsy of an acutely ill patient and the tick removed from him prior to the disease development. The tick has been identified as Haemaphysalis spp. The clinical picture was that of a spotted fever group rickettsiosis and a seroconversion was noted with R. heilongjiangensis antigen . Screening testing of both species of Haemaphysalis ticks inhabiting Russian Far Eastern regions showed that up to 28.13% of H. concinnae and 4.48% of H. japonica douglasii ticks harbor R. heilongjiangensis. It has been concluded that H. concinnae may serve as the main vector for the transmission of R. heilongjiangensis. H. japonica douglasii ticks harbor several varieties of rickettsiae. DNA of “Candidatus Rickettsia tarasevichiae,” previously found in Ixodes persulcatus ticks, was amplified from one male tick. Two sequenced complete gltA genes belong to the novel spotted fever group rickettsial species provisionally called here “Candidatus Rickettsia principis” variants Hjd54 and Hjd61. The rate of infection has been found to be not higher than 1.5%.

Abstract: 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.