Prevalence of Borrelia burgdorferi sensu lato and Borrelia miyamotoi in ixodid ticks in the Far East of Russia

<i>Borrelia burgdorferi</i> sensu lato (s.l.) DNA was detected by PCR in <i>Ixodes persulcatus</i> Schulze, 1930, <i>Haemaphysalis concinna</i> Koch, 1844<i>, Haemaphysalis japonica douglasi</i> Nuttall et Warburton, 1915 and <i>Dermacentor silvarum</i> Olenev, 1932 ticks collected in the Amur region, the Jewish Autonomous region, the Sakhalin region and on the Khabarovsk territory. Infection rate of <i>I. persulcatus</i> with <i>B. burgdorferi</i> s.l. 10-69% exceeded the corresponding values of three other tick species in all examined regions during 1999-2014 despite different tick abundance and dominance structure. Bacterial loads estimated on the base of quantitative real time PCR varied from 10² to 10⁹ genome-equivalents per a tick with maximal values for <i>I. persulcatus</i> and <i>H. japonica.</i> Phylogenetic analysis of 16S rRNA gene and 5S-23S rRNA intergenic spacer nucleotide sequences revealed two species: 1) <i>Borrelia garinii</i> of Asian type NT29 with several isolates of European type 20047; 2) <i>Borrelia afzelii</i> with identical sequences of the majority of studied isolates and VS461 reference strain in all regions except the Sakhalin Island where <i>B. afzelii</i> was not found<i>. Borrelia miyamotoi</i> of the relapsing fever group was detected as monoinfection or in combination with <i>B. burgdorferi</i> s.l. in 4.0 ± 0.9% and 4.8 ± 0.9% <i>I. persulcatus</i> ticks, respectively. Multiple locus sequence analysis of three fragments of 16S rRNA, glpQ and p66 genes proved that all the Far Eastern <i>B. miyamotoi</i> isolates belonged to the Asian type identical to FR64b strain (GenBank CP004217) from Japan. Wide distribution of <i>Borrelia</i> DNA in ticks, relative genetic homogeneity with similar sequences of the coding regions and the intergenic spacer of <i>Borrelia</i> wild isolates and temporal stability with high homology levels of the Far Eastern isolates of <i>B. garinii</i>, <i>B. afzelii</i> and <i>B. miyamotoi</i> with previously described spirochetes from the surrounding regions of Russia, China and Japan allowed us to suggest multiple ecological niches as the stability factor of the parasitic system.