Tick-Borne Relapsing Fever

Aka: Tick-Borne Relapsing Fever, Relapsing Fever

1. See Also
   1. Tick-Borne Illness
   2. Borrelia
2. 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
3. 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
4. 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. Chills
      4. Nausea or Vomiting
      5. Abdominal Pain
5. Signs
   1. Hepatomegaly (10%)
   2. Splenomegaly (6%)
   3. Meningitis (2%)
   4. Pneumonitis
   5. Myocarditis
   6. Iridiocyclitis
   7. Cranial Nerve palsy (e.g. Bell's Palsy, deafness)
   8. Altered Level of Consciousness (Delirium, coma)
6. 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
7. 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
8. Labs: If indicated
   1. Myocarditis suspected
      1. EKG with Prolonged QT interval (QTc)
   2. Meningitis suspected
      1. CSF mononuclear Pleocytosis and increased CSF Protein
9. Management
   1. 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
   2. Louse-borne Infection
      1. Tetracycline 500 mg oral or IV once OR
      2. Erythromycin 500 mg oral or IV once
10. 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
    2. Acute Respiratory Distress Syndrome (ARDS)
    3. Encephalopathy
11. 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
12. Prevention
    1. See Prevention of Tick-borne Infection
    2. Spray susceptible buildings with Malathion 0.5%
    3. Keep home free of rodents
13. References
    1. Dworkin (2002) Med Clin North Am 86:417-33 [PubMed]
    2. Roscoe (2005) Am Fam Physician 72(10):2039-44 [PubMed]