Phylogeographical diversity of Anaplasma phagocytophilum in the Asian part of Russia based on multilocus sequence typing and analysis of the ankA gene

Anaplasma phagocytophilum is a tick-transmitted bacterium that replicates in neutrophil granulocytes and elicits febrile disease in humans and animals; it is widely distributed in the Americas, Europe, Africa, and Asia. A. phagocytophilum is commonly regarded as a single species, but several genetic variants with distinct host distribution and geographical origin have been described. In a previous study, we used multilocus sequence typing (MLST) to characterize 25 A. phagocytophilum strains from Ixodes spp. ticks collected in the Asian part of Russia. The obtained concatenated sequences formed two separate clades reflecting their Asiatic origin and/or the vector species. As one of the clades was related to A. phagocytophilum strains from European voles and shrews, we here extended our analysis to seven samples from the northern red-backed vole Myodes rutilus and included 38 additional strains of Asiatic origin from Ixodes persulcatus, I. pavlovskyi, and their hybrids. Further, the ankA gene was sequenced in 59 A. phagocytophilum strains from ticks and voles. The Russian strains belonged to the two new MLST clusters 5 (38/70) and 6 (32/70), previously referred to as clades within clusters 1 and 3, respectively. The total number of sequence types (STs) found was 27 including 12 new STs. The ankA sequences were unique and formed two new clusters: cluster 8 (34/59) and cluster 10 (25/59). The concordance between MLST and ankA-based typing was 100%. This means that at least two distinct genetic groups of A. phagocytophilum circulate in the Asian Part of Russia whose reservoir hosts and transmission cycles have to be further elucidated.