Detection and genetic characterization of relapsing fever spirochete Borrelia miyamotoi in Estonian ticks

Abstract

During the years 2008-2010 I. ricinus and I. persulcatus ticks were collected from 64 sites in mainland Estonia and on the island Saaremaa. Presence of B. miyamotoi was found in 0.9% (23/2622) of ticks. The prevalence in I. persulcatus and I. ricinus ticks differed significantly, 2.7% (15/561) and 0.4% (8/2061), respectively. The highest prevalence rates were in found South-Eastern Estonia in an area of I. persulcatus and I. ricinus sympatry and varied from 1.4% (1/73) to 2.8% (5/178). Co-infections with B. burgdorferi s.l. group spirochetes and tick-borne encephalitis virus were also revealed. Genetic characterization of partial 16S rRNA, p66 and glpQ genes demonstrated that Estonian sequences belong to two types of B. miyamotoi and cluster with sequences from Europe and the European part of Russia, as well as with sequences from Siberia, Asia and Japan, here designated as European and Asian types, respectively. Estonian sequences of the European type were obtained from I. ricinus ticks only, whereas the Asian type of B. miyamotoi was shown for both tick species in the sympatric regions.

Figure 1. Tick sampling sites in Estonia and the prevalence of B. miyamotoi.

The areas of I. ricinus and I. persulcatus distribution and sympatry are indicated. The ticks’ collection sites indicated by dots.

Figure 2. Phylogenetic trees based on the partial sequences of 16S rRNA, p66 and glpQ genes.

The Maximum Likelihood model was used for phylogenetic tree reconstruction of the partial A) 16S rRNA (1106 bp), B) p66 (349 bp and 355 bp for “I. persulcatus”-type and “I. ricinus”-type, respectively) and C) glpQ genes (379 bp). Only quartet puzzling support values >70% are shown. Samples sequenced in the present study are underlined.