Borrelia miyamotoi Disease (BMD)

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

  • An additional contrast is that BMD may occur shortly after attachment of an infected tick, while Lyme disease risk is highest after 36–48 hours of attachment and feeding on a human host

• 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

• Polymerase chain reaction (PCR) of blood or cerebrospinal fluid (CSF) samples

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

  • Negative results do not necessarily rule out BMD

• If PCR is not available, spirochetes may sometimes be visualized on a blood smear using Wright or Giemsa-stain or by darkfield microscopy of CSF

• 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