Borrelia miyamotoi—An Emerging Human Tick-Borne Pathogen in Europe

Borrelia miyamotoi is classified as a relapsing fever spirochete. Although B. miyamotoi is genetically and ecologically distinct from Borrelia burgdorferi sensu lato, both microorganisms are transmitted by the same Ixodes tick species. B. miyamotoi was detected in I. persulcatus ticks in 1994 in Japan. A phylogenetic analysis based on selected sequences of B. miyamotoi genome revealed genetic differences between isolates from Asia, North America, and Europe, which are clearly separated into three genotypes. Symptomatic human cases of Borrelia miyamotoi disease (BMD) were first reported in 2011 in Russia and then in North America, Europe, and Asia. The most common clinical manifestation of BMD is fever with flu-like symptoms. Several differences in rare symptoms (thrombocytopenia, monocytosis, cerebrospinal fluid pleocytosis, or symptoms related to the central nervous system) have been noted among cases caused by Asian, European, and American types of B. miyamotoi. BMD should be considered in the diagnosis of patients after tick bites, particularly with meningoencephalitis, without anti-Borrelia antibodies in the cerebrospinal fluid. This review describes the biology, ecology, and potential of B. miyamotoi as a tick-borne pathogen of public health concern, with particular emphasis on Europe.