Tick-Born Relapsing Fever and Genespecies Diversity of Borrelia: Current Status

Relevance. Tick-borne relapsing fevers caused by Borrelia species pathogenic for humans are not well understood. Aim of this review is to assess the genetic diversity of Borrelia with special attention to the relapsing fever group and phylogenetically related species carried by ticks. The review also provides up-to-date information on the main vectors and their geographic distribution, reservoirs of borrelia – pathogens, and potential pathogens of tick-borne recurrent fevers. Conclusions. New types of Borrelia, including a candidate, of relapsing fever clade and related phylogenetic lines/groups, which are carried not only by argasid, but also by solid-body ixodids ticks, deserve further study. The preservation of the epidemic potential of tick-borne relapsing fever can be facilitated by climatic changes, and poorly studied adaptation mechanisms of Borrelia to the range of vectors.