Vector

Tick-Borne Relapsing Fever

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Tick-Borne Relapsing Fever, Louse-Borne Relapsing Fever, Relapsing Fever, Borrelia Recurrentis, Borrelia Hermsii, Borrelia Turicate, Borrelia Miyamotoi

  • See Also
  1. Tick-Borne Illness
  2. Borrelia
  3. Vector Borne Disease
  4. Prevention of Tick-borne Infection
  5. Tick Removal
  • Epidemiology
  1. Rare: <500 cases reported in U.S. in the last 25 years
  2. Region
    1. U.S. West of the Mississippi River
    2. More common in mountains
  • Pathophysiology
  1. Cause
    1. Spirochetes in Borrelia genus
    2. Total of 18 Borrelia species causing Relapsing Fever (with all but 1 transmitted by tick)
  2. Vectors
    1. Soft Ticks (Ornithodoros genus)
      1. Other Borrelia species cause Relapsing Fever in Africa and Russia (e.g. B hispanica, B. duttonii)
      2. Borrelia Hermsii (reservoir: Squirrels and chipmunks in U.S. western mountains)
      3. Borrelia Turicate (reservoir: Cattle, rodents, pigs in south central and southwestern U.S.)
      4. Borrelia Miyamotoi (Northeast and Northern midwest)
    2. Body Lice (pediculus humanus, human to human transmission, only louse-borne Borrelia infection)
      1. Borrelia Recurrentis
  3. Exposure
    1. Mountain cabin with rodents
    2. Cave exploration
    3. Work under buidlings
  4. Relapsing Fever Pattern Mechanisms
    1. Antigenic Variation (primary mechanism)
      1. Borrelia serotypes can change their surface Antigens to initially evade Antibody detection
    2. Infection with multiple Borrelia serotypes
      1. Infections often involve multiple Borrelia serotypes
      2. As one serotype is cleared, another proliferates with different surface Antigens
    3. Dormancy
      1. Borrelia may lie dormant in liver, Spleen, CNS, marrow and then reactivate
  • Symptoms (follows 7 day Incubation Period)
  1. Fever
    1. Sudden onset, over 102.5 F (39.2 C)
    2. May rise over 104 F
    3. Pattern
      1. Fever for 3 to 6 days
      2. Febrile period ends with 30 minute crisis period
        1. Brief spike in pulse and Blood Pressure
        2. Sweats occur as the fever abates
      3. Fever recurs every 4 to 14 days (8 day average)
        1. Associated symptoms accompany Recurrent Fever and last 3-6 days per episode
        2. Interval between episodes lengthens overtime, with each recurrent episode trending to more mild
  2. Associated symptoms
    1. Headache
    2. Myalgias and Arthralgias
    3. Shaking Chills (rigors)
    4. Profuse diaphoresis (as fever resolves days 3 to 6)
    5. Nausea or Vomiting
    6. Abdominal Pain
  • Signs
  1. See Complications (below)
  2. Tachycardia
  3. Hypertension
  4. Hepatomegaly (10%)
  5. Splenomegaly (6%)
  • Labs
  • Diagnosis
  1. Test Sensitivity is highest during febrile periods
  2. Immunofluorescence and PCR are not widely available
  3. Microscopic exam of blood, CSF other body fluid
    1. Thick and thin smears stained with Wright's or Giemsa (or dark microscopy)
    2. Spirochetes identified
  4. Blood Cultures during febrile period
    1. Requires special media
  • Labs
  • Other findings
  1. Complete Blood Count
    1. Anemia
    2. Slight Leukocytosis
    3. Thrombocytopenia
  2. Liver Function Tests
    1. Increased Unconjugated Bilirubin
    2. Increased Aminotransferases
  3. Urinalysis
    1. Proteinuria and Hematuria
  • Labs
  • If indicated
  1. Myocarditis suspected
    1. EKG with Prolonged QT interval (QTc)
  2. Meningitis suspected
    1. CSF mononuclear Pleocytosis and increased CSF Protein
  • Management
  1. Risk of Jarisch-Herxheimer Reaction with treatment (see below)
  2. Tick-Borne Infection
    1. Doxycycline 100 mg oral or IV twice daily for 7-10 days (preferred) OR
      1. Children: 4.4 mg/kg/day divided twice daily (up to 100 mg/dose)
    2. Erythromycin 500 mg orally qid for 7-10 days OR
    3. Penicillin G 5 MU IV every 6 hours for 7 to 10 days
  3. Louse-borne Infection
    1. Tetracycline 500 mg oral or IV once OR
    2. Erythromycin 500 mg oral or IV once
  4. Central Nervous System Involvement
    1. Ceftriaxone IV OR
    2. Penicillin G IV
  • Complications
  1. Jarisch-Herxheimer Reaction (54% of treated cases)
    1. Occurs with treatment of Spirochete disease (similar to Syphilis treatment)
    2. Onset within 2 hours of starting treatment
    3. Observe for 12 to 24 hours after starting treatment
  2. Neurologic
    1. Meningitis (2%)
    2. Encephalopathy
    3. Cranial Nerve palsy (e.g. Bell's Palsy, Deafness)
    4. Altered Level of Consciousness (Delirium, coma)
  3. Cardiopulmonary
    1. Acute Respiratory Distress Syndrome (ARDS)
    2. Pneumonitis
    3. Myocarditis
  4. Ocular
    1. Iridiocyclitis
    2. Iritis
    3. Uveitis
  • Prognosis
  1. Mortality <1% in treated cases
  2. Poor prognostic factors
    1. Myocarditis
    2. Altered Level of Consciousness
    3. Poor liver function
    4. Bleeding complications from multiple sites
  • Prevention
  1. See Prevention of Tick-borne Infection
  2. Spray susceptible buildings with Malathion 0.5%
  3. Keep home free of rodents
  • References
  1. (2025) Sanford Guide, accessed on 3/7/2025
  2. Dworkin (2002) Med Clin North Am 86:417-33 [PubMed]
  3. Pace (2020) Am Fam Physician 101(9): 530-40 [PubMed]
  4. Roscoe (2005) Am Fam Physician 72(10):2039-44 [PubMed]