Tick-Borne Relapsing Fever

Aka: Tick-Borne Relapsing Fever, Relapsing Fever

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II. 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

III. Pathophysiology

  1. Cause
    1. Spirochete in Borrelia genus
  2. Vectors
    1. Soft Ticks (Ornithodoros genus)
      1. Other Borrelia species cause Relapsing Fever in Africa and Russia
      2. Borrelia hermsii (reservoir: Squirrels and chipmunks)
      3. Borrelia tunicate (reservoir: Cattle, rodents, pigs)
      4. Borrelia miyamotoi
    2. Body Lice (human to human transmission)
      1. Borrelia recurrentis
  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

IV. 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
    2. Myalgias and Arthralgias
    3. Shaking Chills (rigors)
    4. Profuse diaphoresis (as fever resolves)
    5. Nausea or Vomiting
    6. Abdominal Pain

V. Signs

  1. See Complications (below)
  2. Tachycardia
  3. Hypertension
  4. Hepatomegaly (10%)
  5. Splenomegaly (6%)

VI. Labs: Diagnosis

  1. Test Sensitivity is highest during febrile periods
  2. 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
  3. Blood Cultures during febrile period
  4. Immunofluorescence and PCR not widely available

VII. 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

VIII. Labs: If indicated

  1. Myocarditis suspected
    1. EKG with Prolonged QT interval (QTc)
  2. Meningitis suspected
    1. CSF mononuclear Pleocytosis and increased CSF Protein

IX. 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
    2. Erythromycin 500 mg orally qid for 7-10 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

X. 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

XI. 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

XII. Prevention

  1. See Prevention of Tick-borne Infection
  2. Spray susceptible buildings with Malathion 0.5%
  3. Keep home free of rodents

XIII. References

  1. Dworkin (2002) Med Clin North Am 86:417-33 [PubMed]
  2. Pace (2020) Am Fam Physician 101(9): 530-40 [PubMed]
  3. Roscoe (2005) Am Fam Physician 72(10):2039-44 [PubMed]

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