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Key Features

  • An emerging spirochetal disease caused by B miyamotoi subspecies, which are taxonomically closely related to Borrelia recurrentis and Borrelia hermsii, the pathogens of relapsing fever

  • Similarities between BMD and Lyme disease

    • Both transmitted by Ixodes ticks

    • Commonly found in same regions

  • Differences between BMD and Lyme disease

    • BMD: Peak months of risk to humans is later in summer to early fall because B miyamotoi can be vertically transmitted to larval Ixodes ticks

    • Lyme disease: Peak months of risk to humans is early summer because Borrelia burgdorferi is transmitted by the nymph or adult tick

    • Prevalence of B miyamotoi 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

  • Avoidance of tick exposure is best prevention

Clinical Findings

  • Fever occurs in almost all cases

  • Fatigue, myalgia, chills, and nausea

  • Meningoencephalitis, headache or cognitive impairment can predominate in more severe disease or in elderly patients

  • Rashes are uncommon (< 10% of cases)

  • Differential diagnosis

    • Lyme disease without rash

    • Human granulocytic anaplasmosis

    • Babesiosis

    • Ehrlichiosis

Diagnosis

  • Leukopenia

  • Thrombocytopenia

  • Elevated liver biochemical tests

  • PCR of blood or CSF samples

    • When drawn during acute disease, may be helpful to detect B miyamotoi

    • Negative results do not necessarily rule out BMD

  • If using the recommended two step testing algorithm for B burgdorferi (enzyme immunoassay [EIA] followed by immunoblot), the EIA may be positive in BMD due to cross-reactivity but the confirmatory immunoblot will be negative

  • Glp-Q protein-based assay 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

Treatment

  • Doxycycline 100 mg orally twice daily for 14 days

  • Ceftriaxone 2 g intravenously once daily for 2–4 weeks may be given for severe or CNS disease

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