Tickborne Relapsing Fever (TBRF)

(Soft Tick Relapsing Fever)


Borrelia hermsii, B. turicatae

Where Found

In the United States, TBRF usually occurs in mountainous areas of Western states, where it is associated with exposure to soft ticks in rustic cabins (B. hermsii), and in Texas, where it is most often associated with exposure to soft ticks in caves (B. turicatae).

Incubation Period

Approximately 7 days (range 4-21), with recurrent febrile episodes that last around 3 days and are separated by afebrile periods of approximately 7 days.

Signs and Symptoms

TBRF most commonly presents with fever, headache, and myalgias. As with other borrelioses, neurologic involvement is possible, including meningoencephalitis, cranial neuritis and ocular manifestations. Acute respiratory distress syndrome is a rare complication.

  • High fever with relapses
  • Chills/rigors
  • Sweats
  • Headache
  • Myalgia/arthralgia
  • Dizziness
  • Nausea/vomiting
  • Facial palsy (rarely)

Note: TBRF can be transmitted transplacentally and has been associated with pregnancy complications including spontaneous abortion, premature birth, and neonatal death.

General Laboratory Findings

  • Leukocytosis
  • Thrombocytopenia
  • Mild hyperbilirubinemia
  • Elevated erythrocyte sedimentation rate
  • Slightly prolonged prothrombin time (PT) and partial thromboplastin time (PTT)

Laboratory Diagnosis

Tests may include the following:

  • Visualization of spirochetes by microscopy of peripheral blood obtained during a febrile episode prior to treatment.
  • Molecular testing, such as PCR. Molecular tests should be performed as early as possible, ideally prior to treatment or soon after. PCR testing is more sensitive than microscopy.
  • Serologic testing by immunofluorescence assay (IFA), enzyme immunoassay (EIA), or immunoblot.

NOTE: Serologic tests and some commercially available PCR tests cross-react with other Borrelia species, including B. burgdorferi, the cause of Lyme disease.


Treatment data for patients with TBRF are limited. Consider the following regimens for nonpregnant patients who do not have neurologic complications. In pregnant individuals or when neurologic involvement is present, initial parenteral therapy with a beta-lactam is advised; treatment should be continued for 10-14 days with close monitoring given the potential for severe complications.

TFRF Treatment regimens
Age category Drug Dosage Duration (days)
Adults Doxycycline, oral or intravenous (first-line) 100 mg every 12 hours 10
Azithromycin, oral 500 mg daily 10
Penicillin G, intravenous 4,000,000 units every 6 hours 10
Ceftriaxone, intravenous 2 g daily 10
Children Doxycycline, oral or intravenous (first-line) 2.2 mg/kg per dose, every 12 hours, maximum 100 mg/dose 10
Azithromycin, oral 10 mg/kg daily, maximum 500 mg/day 10
Penicillin G, intravenous 50,000-100,000 units/kg every 6 hours, maximum 4,000,000 units/dose 10
Ceftriaxone, intravenous 50-75 mg/kg daily, maximum 2 g/day 10

NOTE: When initiating antibiotic therapy, all patients should be observed during the first 4 hours of treatment for a Jarisch-Herxheimer reaction.

See www.cdc.gov/relapsing-fever/clinicians for detailed treatment information.


Centers for Disease Control and Prevention. Acute respiratory distress syndrome in persons with tickborne relapsing fever—Three states, 2004–2005. MMWR Morb Mortal Wkly Rep. 2007;56(41): 1073–1076.

Centers for Disease Control and Prevention. Tickborne relapsing fever—United States, 1990–2011. MMWR Morb Mortal Wkly Rep. 2015;64(3):58-60.

Dworkin MS, Anderson DE Jr, Schwan TG, et al. Tick-borne relapsing fever in the northwestern United States and southwestern Canada. Clin Infect Dis. 1998;26(1):122-31.

Hashavya S, Gross I, Gross M, et al. Tickborne Relapsing Fever, Jerusalem, Israel, 2004-2018. Emerg Infect Dis. 2020;26(10):2420-2423.

Lyme Disease and Other Nonsyphilitic Spirochetal Infections. In: Jameson J, Fauci AS, Kasper DL, Hauser SL, Longo DL, Loscalzo J. eds. Harrison’s Manual of Medicine, 20e. McGraw Hill; 2020.

Yagupsky P, Moses S. Neonatal Borrelia species infection (relapsing fever). Am J Dis Child. 1985 Jan;139(1):74-6.