Borrelia miyamotoi infection in nature and in humans

Abstract

Borrelia miyamotoi is a relapsing fever Borrelia group spirochete that is transmitted by the same hard-bodied (ixodid) tick species that transmit the agents of Lyme disease. It was discovered in 1994 in Ixodes persulcatus ticks in Japan. B. miyamotoi species phylogenetically cluster with the relapsing fever group spirochetes, which usually are transmitted by soft-bodied (argasid) ticks or lice. B. miyamotoi infects at least six Ixodes tick species in North America and Eurasia that transmit Lyme disease group spirochetes and may use small rodents and birds as reservoirs. Human cases of B. miyamotoi infection were first reported in 2011 in Russia and subsequently in the United States, Europe and Japan. These reports document the public health importance of B. miyamotoi, as human B. miyamotoi infection appears to be comparable in frequency to babesiosis or human granulocytic anaplasmosis in some areas and may cause severe disease, including meningoencephalitis. The most common clinical manifestations of B. miyamotoi infection are fever, fatigue, headache, chills, myalgia, arthralgia, and nausea. Symptoms of B. miyamotoi infection generally resolve within a week of the start of antibiotic therapy. B. miyamotoi infection should be considered in patients with acute febrile illness who have been exposed to Ixodes ticks in a region where Lyme disease occurs. Because clinical manifestations are nonspecific, etiologic diagnosis requires confirmation by blood smear examination, PCR, antibody assay, in vitro cultivation, and/or isolation by animal inoculation. Antibiotics that have been used effectively include doxycycline for uncomplicated B. miyamotoi infection in adults and ceftriaxone or penicillin G for meningoencephalitis.

Keywords: Borrelia miyamotoi; Ixodes; Lyme disease; relapsing fever; spirochete; tick-borne disease.

Figure 1

Phylograms of aligned syntenic chromosome sequences of nine selected relapsing fever group and Lyme disease group Borrelia species by BioNJ neighbor-joining protocol for observed differences at 850,377 ungapped sites by a procedure described in reference . Nodes with bootstrap values of ≥70% support after 100 replicates are shown. The bar represents nucleotide substitutions per site. The organisms (with GenBank accession numbers) were B. miyamotoi strain LB-2001 from Connecticut, USA (CP006647); B. miyamotoi strain FR64b from Japan (CP004217); North American tickborne relapsing fever species B. turicatae strain 91E135 (CP000049), B. parkeri strain HR1 (CP007022), B. hermsii strain DAH of genomic group I (CP000048), B. hermsii strain YOR of genomic group II (CP004146); the Old World tickborne relapsing fever species B. crocidurae strain DOU (CP004267); and two Lyme disease species, B. burgdorferi strain B31 (AE000783) and B. afzelii strain PKo (CP002933).

Figure 2

Approximate current geographic distributions of the main tick vectors of Borrelia miyamotoi: I. scapularis (green) and I. pacificus (brown) in North America and I. ricinus (blue) and I. persulcatus (red) in Eurasia. I. ovatus and I. pavlovskyi are two other species that have been shown to carry B. miyamotoi.

Figure 3

A. B. miyamotoi grown In vitro (phase contrast, 100x [bar 5 um]), B. B. miyamotoi grown In vitro (dark-field, 40x [bar 15 um]), C. B. miyamotoi in infected mouse blood (phase contrast of wet mount of plasma [400x]).