Molecular detection and phylogenetic analysis of Borrelia miyamotoi strains from ticks collected in the capital region of Finland

Abstract

<p><em>Borrelia miyamotoi</em> is an emerging pathogen that shares high similarity with relapsing fever <em>Borrelia,</em> but has an atypical clinical presentation. Within the framework of tick-borne disease surveillance in Finland, human serum samples suspected for tick-borne encephalitis (n=974) and questing ticks (n=739) were collected from the capital region in Finland to determine the prevalence of <em>B. miyamotoi.</em> All tested human samples were negative and 5 (0.68 %) <em>Ixodes ricinus</em> ticks were positive for <em>B. miyamotoi</em>. Partial sequencing of the flagellin (<em>flaB</em>) gene of 3 positive samples and 27 <em>B. miyamotoi</em>-positive tick samples obtained from previous studies across Finland were amplified, sequenced, and included in the phylogenetic analysis.</p><p>The phylogenetic tree revealed that most <em>B. miyamotoi</em> strains isolated from ticks in Finland share high similarity with other European strains, including strains related to human infection. Possible disease transmission may occur during exposure to tick bites. A single strain collected from an <em>I. persulcatus</em> tick in Pajujärvi grouped with an outlier of <em>B. miyamotoi</em> strains isolated from Russia and Far East Asian countries. Further studies should investigate the pathogen’s role in human infection in Finland.</p><p>Another important finding is the occurrence of <em>I. persulcatus</em> ticks (8%) collected by crowdsourcing from the coastal southern part of Finland. This suggests a regular introduction and a possible wide expansion of this tick species in the country. This could be associated with transmission of new pathogens.</p>