Infectious Disease Book

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Tick-Borne Relapsing FeverAka: Relapsing Fever

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  1. Epidemiology
    1. Rare: <500 cases reported in U.S. in last 25 years
    2. Region
      1. U.S. West of the Mississippi River
      2. More common in mountains
  2. Pathophysiology
    1. Cause: Spirochete in Borrelia genus
      1. Borrelia hermsii (hosts: Squirrels and chipmunks)
      2. Borrelia turicata (hosts: Cattle, rodents, pigs)
    2. Tick vector: Ornithodoros genus
    3. Exposure
      1. Mountain cabin with rodents
      2. Cave exploration
      3. Work under buidlings
    4. Relapsing fever
      1. Infections often involve multiple Borrelia serotypes
      2. As one serotype is cleared, another proliferates
      3. May lie dormant in liver, spleen, CNS, marrow
      4. Alternating serotypes, dormancy cause relapsing fever
  3. 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
    2. Associated symptoms
      1. Headache, Myalgias, Arthralgias, and chills
      2. Nausea, Vomiting and Abdominal Pain
  4. Signs
    1. Hepatomegaly (10%) or Splenomegaly (6%)
    2. Meningitis (2%)
    3. Pneumonitis
    4. Myocarditis
    5. Iridiocyclitis
    6. Cranial Nerve palsy (e.g. Bell's Palsy, deafness)
    7. Altered Level of Consciousness (Delirium, coma)
  5. Labs: Diagnosis
    1. Microscopic exam of blood, CSF other body fluid
      1. Thick and thin smears stained with Wright's or Giemsa
      2. Spirochetes identified
    2. Blood Cultures during febrile period
    3. Immunofluorescence and PCR not widely available
  6. 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
  7. Labs: If indicated
    1. Myocarditis suspected
      1. EKG with Prolonged QT interval (QTc)
    2. Meningitis suspected
      1. CSF mononuclear Pleocytosis and increased CSF Protein
  8. Management
    1. First line
      1. Doxycycline 100 mg orally bid for 7-10 days
      2. Tetracycline 500 mg orally qid for 7-10 days
    2. Alternative
      1. Erythromycin 500 mg orally qid for 7-10 days
      2. Penicillins (IV only)
  9. Complications
    1. Jarisch-Herxheimer Reaction (54% of treated cases)
      1. Occurs with treatment
      2. Onset within 2 hours of starting treatment
      3. Observe for 12 to 24 hours after starting treatment
  10. 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
  11. Prevention
    1. See Prevention of Tick-borne Infection
    2. Spray susceptible buildings with Malathion 0.5%
    3. Keep home free of rodents
  12. References
    1. Dworkin (2002) Med Clin North Am 86:417
    2. Roscoe (2005) Am Fam Physician 72(10):2039

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