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B miyamotoi disease is an emerging spirochetal disease caused by B miyamotoi subspecies, which are taxonomically closely related to Borrelia recurrentis and Borrelia hermsii, the agents of relapsing fever. Like Lyme disease, it is tick-borne via Ixodes ticks.

B miyamotoi is commonly found in regions with Lyme disease. It was initially identified as a cause of febrile illness in Russian adults and has subsequently been documented in North America and Europe as well.

Unlike B burgdorferi, the causative agent of Lyme disease in which the nymph or adult tick transmits the infection, B miyamotoi can be vertically transmitted to larval Ixodes ticks. In the United States, this can cause a shift in the peak months during which the risk of human disease is highest. The peak season for Lyme disease is late fall while the peak for B miyamotoi disease is into the summer and early fall.

Prevalence of B miyamotoi in different species of Ixodes ticks in the northern United States is 5% or less, compared to up to 30% for B burgdorferi. Rodents and birds are reservoirs for B miyamotoi.

CLINICAL FINDINGS

A. Symptoms and Signs

Fever occurs in almost all cases. In contrast to Lyme disease, rashes are uncommon (less than 10% of cases). Symptoms may include severe systemic symptoms of fatigue, myalgia, chills, and nausea. In more severe disease or in elderly or immunocompromised patients, meningoencephalitis, headache, or cognitive impairment can predominate. While the fever of B miyamotoi disease can wax and wane, there is not an acute presentation as in true relapsing fever disease due to B recurrentis or B hermsii.

B. Laboratory Findings

Laboratory findings include leukopenia, thrombocytopenia and elevated liver biochemical tests. PCR of blood or CSF samples drawn during acute disease may be helpful to detect B miyamotoi; negative results do not necessarily rule out B miyamotoi disease because laboratories may vary in expertise.

If using the recommended two step testing algorithm for B burgdorferi (EIA followed by immunoblot), the EIA may be positive in B miyamotoi disease due to cross-reactivity but the confirmatory immunoblot will be negative. This may be an indication that B miyamotoi, rather than B burgdorferi, is the causative pathogen. Further testing can then be done using a Glp-Q protein-based assay that can distinguish between B burgdorferi and B miyamotoi. However, these tests may also be positive for the Borrelia of relapsing fever. Paired acute and convalescent sera may be most useful for confirming the diagnosis in hindsight.

DIFFERENTIAL DIAGNOSIS

Lyme disease without rash, human granulocytic anaplasmosis, babesiosis, and ehrlichiosis should be differentiated from B miyamotoi disease.

TREATMENT

Treatment is with doxycycline 100 mg orally twice daily for 14 days, which is similar ...

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