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The specimens of 3552 questing adult Ixodes persulcatus and 1698 blood/tissue samples of small mammals collected in Ural, Siberia, and Far East of Russia were assayed for the presence of Anaplasma phagocytophilum by nested PCR based on the 16S rRNA gene. Totally, A. phagocytophilum was detected in 112 tick and 88 mammalian samples. The nucleotide sequences of the 16S rRNA gene and groESL operon (1244-1295 bp) were determined for A. phagocytophilum samples from 65 ticks and 25 small mammals. Six different 16S rRNA gene variants differing by 1-5 nucleotide substitutions were detected, and only one variant matched the sequences deposited in GenBank. Analysis of groESL sequences allowed the A. phagocytophilum samples to be divided into three groups; moreover, the samples from different groups also differed in the 16S rRNA gene sequences. The A. phagocytophilum sequences from group I were detected in 11 Myodes spp. samples from West Siberia and Far East and in 19 I. persulcatus samples from all examined regions; from group II, in 10 samples of Myodes spp. and common shrews (Sorex araneus) from Ural; and from group III, in four samples of Asian chipmunks (Tamias sibiricus) from West Siberia and Far East; and in 46 I. persulcatus samples from all examined regions. The nucleotide sequences of A. phagocytophilum groESL operon from groups I and II were strictly conserved and formed with A. phagocytophilum groESL sequence from a Swiss bank vole (Myodes glareolus) (GenBank accession no. AF192796), a separate cluster on the phylogenetic tree with a strong bootstrap support. The A. phagocytophilum groESL operon sequences from group III differed from one another by 1-4 nucleotides and formed a separate branch in the cluster generated by European A. phagocytophilum strains from roe deer (Capreolus capreolus) and Ixodes ricinus ticks.

Totally, 2590 questing adult Ixodes persulcatus ticks and 1458 small mammals from Ural, Siberia, and the Far East as well as 53 Haemaphysalis concinna, 136 Haem. japonica, and 43 Dermacentor silvarum ticks--exclusively adults--from the Far East were examined for the presence of Ehrlichia and Anaplasma by nested PCR based on the 16S rRNA gene. Both Anaplasma phagocytophilum and Ehrlichia muris were found in I. persulcatus and small mammals from all the studied regions. Myodes spp., Microtus spp., Sorex araneus, Apodemus peninsulae, and Tamias sibiricus were naturally infected with An. phagocytophilum and E. muris. Five of the examined I. persulcatus and 5 of the examined wild rodents from Siberia and the Far East were infected with 'Candidatus Neoehrlichia mikurensis'. The determined 16S rRNA gene sequences of 'Candidatus Neoehrlichia mikurensis' were identical to the sequences of Japanese isolates, while the determined groESL sequences were unique. A new Ehrlichia sp. variant closely related to the Ehrlichia sp. EHf669 found in Haem. flava from Japan was detected in 11% of Haem. japonica ticks. New Anaplasmataceae bacteria genetically distinct from the known species of this family were found in 3 adult Derm. silvarum from the Far East and in 2 I. persulcatus from Siberia and the Far East. In the Far East, about 15% of the captured small mammals were naturally infected with recently discovered Ehrlichia sp. Khabarovsk. Ehrlichia sp. Khabarovsk was found in about 20% of Myodes spp. and S. araneus but was undetectable in any of the 236 studied Ap. peninsulae. A three-year study has demonstrated that An. phagocytophilum and E. muris were detectable in small mammals from the Far East captured only after the beginning of the tick activity season, from May to November. Ehrlichia sp. Khabarovsk was found in mammals trapped in all the examined periods, from February to November., (Copyright © 2010 Elsevier GmbH. All rights reserved.)