Genetic variability of Anaplasma phagocytophilum in ticks and voles from Ixodes persulcatus/Ixodes trianguliceps sympatric areas from Western Siberia, Russia.

Anaplasma phagocytophilum is a causative agent of granulocytic anaplasmosis in different mammals. The presence of A. phagocytophilum was assayed in Ixodes persulcatus, Ixodes trianguliceps ticks and Myodes spp. voles from two I. persulcatus/I. trianguliceps sympatric areas in the Omsk region (Western Siberia, Russia). In total, A. phagocytophilum was found in 42/108 (38.9%) of vole blood samples, 13/34 (38.2%) of I. trianguliceps ticks removed from voles, 1/12 (8.3%) of I. persulcatus removed from voles, and 18/279 (7.2%) of questing I. persulcatus. GroESL operon sequence analysis of positive samples revealed three distinct A. phagocytophilum genetic groups previously identified in ticks and mammals in Russia. Genetic group 1 was found in 6/36 (16.7%) of sequenced positive blood samples; this group was previously revealed in I. persulcatus and Myodes spp. voles in different regions of Russia. Genetic group 2 was found in 30/36 (83.3%) of sequenced positive blood samples and all positive I. trianguliceps; this group was previously revealed only in Myodes spp. voles and common shrews (Sorex araneus) in I. persulcatus/I. trianguliceps sympatric areas in the Northern Ural. Genetic group 3 was found in all positive questing I. persulcatus and one blood sample; this group was previously revealed in I. persulcatus and Siberian chipmunks (Tamias sibiricus). We suppose that I. trianguliceps is the most probable vector for A. phagocytophilum of group 2. Analysis of the msp4 gene, intergenic region DOV1, and some other genetic loci has shown that isolates from different genetic groups significantly differ in all studied loci and that A. phagocytophilum of group 2 is closely related to A. phagocytophilum isolates revealed in voles and I. trianguliceps in Europe. A. phagocytophilum of groups 1 and 2 are the most similar to each other, while A. phagocytophilum of group 3 clusters with European A. phagocytophilum isolates from I. ricinus and various mammalian species.