Tick-Borne Relapsing Fever

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

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II. 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

III. 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

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 (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

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. 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

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
      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

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. (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]

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Ontology: Relapsing Fever (C0035021)

Definition (MSH) An acute infection characterized by recurrent episodes of PYREXIA alternating with asymptomatic intervals of apparent recovery. This condition is caused by SPIROCHETES of the genus BORRELIA. It is transmitted by the BITES of either the body louse (PEDICULUS humanus corporis), for which humans are the reservoir, or by soft ticks of the genus ORNITHODOROS, for which rodents and other animals are the principal reservoirs.
Concepts Disease or Syndrome (T047)
MSH D012061
ICD9 087.9, 087
ICD10 A68.9 , A68
SnomedCT 46107006, 186822003, 186820006, 187374004, 420079008
LNC LA10500-9
English Fevers, Relapsing, Relapsing Fevers, Fever, Relapsing, Relapsing fever, unspecified, Relapsing fever,unspecified, [X]Relapsing fever, unspecified, [X]Relapsing fever,unspecified, relapsing fever, relapsing fever (diagnosis), Unspecified relapsing fever, Relapsing fever NOS, recurrent fever, Relapsing fevers, Relapsing Fever [Disease/Finding], fevers recurrent, Fever;relapsing, relapsing fevers, fever recurrent, fever relapsing, [X]Relapsing fever, unspecified (disorder), Relapsing fever NOS (disorder), febris; recurrens, fever; relapsing, relapsing; fever, Recurrent fever, NOS, Relapsing fever, NOS, Relapsing fever [dup] (disorder), Relapsing Fever, Relapsing fever, Recurrent fever due to Borrelia, Relapsing fever due to Borrelia, Recurrent fever, Relapsing fever (disorder)
Spanish fiebre recidivante (trastorno), fiebre recidivante, Fiebre recurrente no especificada, fiebre recidivante [dup] (trastorno), fiebre recurrente, SAI (trastorno), [X]fiebre recurrente, no especificada (trastorno), [X]fiebre recurrente, no especificada, fiebre recurrente, SAI, fiebre recidivante por Borrelia, fiebre recurrente por Borrelia, Fiebre recurrente, Fiebre Recurrente
Dutch niet-gespecificeerde febris recurrens, febris recurrens, niet-gespecificeerd, febris; recurrens, fever; relapsing, relapsing; fever, Febris recurrens, niet gespecificeerd, febris recurrens, Febris recurrens [Relapsing fever], Febris recurrens
French Fièvre récidivante non précisée, Fièvre récurrente, non précisée, Fièvre récurrente, Spirochétose récurrente
German unspezifisches Rueckfallfieber, Rueckfallfieber, unspezifisch, Rueckfallfieber, nicht naeher bezeichnet, Rueckfallfieber, Febris recurrens, Rückfallfieber
Italian Febbre ricorrente non specificata, Febbre ricorrente
Portuguese Febre recorrente NE, Febre recorrente, Febre Recorrente
Japanese 回帰熱, 詳細不明の回帰熱, 回帰熱、詳細不明, ｶｲｷﾈﾂｼｮｳｻｲﾌﾒｲ, ｶｲｷﾈﾂ, ｼｮｳｻｲﾌﾒｲﾉｶｲｷﾈﾂ
Swedish Återfallsfeber
Czech návratná horečka, Blíže neurčená návratná horečka, Návratná horečka, blíže neurčená, Návratná horečka
Finnish Toisintokuume
Russian VOZVRATNYI TIF, VOZVRATNYI TIF ENDEMICHESKII, VOZVRATNYI TIF EPIDEMICHESKII, ВОЗВРАТНЫЙ ТИФ, ВОЗВРАТНЫЙ ТИФ ЭНДЕМИЧЕСКИЙ, ВОЗВРАТНЫЙ ТИФ ЭПИДЕМИЧЕСКИЙ
Korean 재귀열, 상세불명의 재귀열
Polish Dur powrotny, Zakażenie Borrelia recurrentis, Gorączka powrotna
Hungarian visszatérő láz, Nem meghatározott visszatérő láz, Visszatérő láz, nem meghatározott
Norwegian Tilbakefallsfeber
Derived from the NIH UMLS (Unified Medical Language System)

Ontology: Tick-borne relapsing fever (C0035022)

Concepts Disease or Syndrome (T047)
ICD9 087.1
ICD10 A68.1
SnomedCT 186821005, 10301003
English Relapsing fever, tick-borne, Tick-borne relapsing fever NOS, tick-borne relapsing fever (diagnosis), tick-borne relapsing fever, Tick-borne relaps fever, Tick-borne relapsing fever NOS (disorder), Tick-borne relapsing fever, Tick-borne relapsing fever (disorder), tick-borne; relapsing fever, Tick-borne relapsing fever, NOS, Tick-Born Relapsing Fever
Dutch febris recurrens, overgebracht door teken, door teken overgebrachte febris recurrens, teken; febris recurrens, Door teken overgebrachte febris recurrens
French Fièvre récurrente, transmise par tique, Fièvre récidivante transmise par tique
German Rueckfallfieber, von Zecken uebertragen, von Zecken uebertragenes Rueckfallfieber, Durch Zecken uebertragenes Rueckfallfieber
Italian Febbre ricorrente da zecche
Portuguese Febre recorrente transmitida por carraças
Spanish Fiebre recurrente transmitida por garrapatas, fiebre recurrente transmitida por garrapatas, SAI (trastorno), fiebre recurrente transmitida por garrapatas, SAI, fiebre recidivante transmitida por garrapatas (trastorno), fiebre recidivante transmitida por garrapatas
Japanese ダニ媒介性回帰熱, ﾀﾞﾆﾊﾞｲｶｲｾｲｶｲｷﾈﾂ
Czech Typhus recurrens přenášený klíštětem, Návratná horečka přenášená klíštětem
Korean 진드기 매개 재귀열
Hungarian Visszatérő láz, kullancs által terjesztett, Kullancs-által terjesztett visszatérő láz
Derived from the NIH UMLS (Unified Medical Language System)

Ontology: Louse-borne relapsing fever (C0152061)

Concepts Disease or Syndrome (T047)
ICD9 087.0
ICD10 A68.0
SnomedCT 14683004
English Relapsing fever, louse-borne, louse-borne relapsing fever (diagnosis), louse-borne relapsing fever, Louse-borne relaps fever, Relapsing fever due to Borrelia recurrentis, Louse-borne relapsing fever, Louse-borne relapsing fever (disorder), disease (or disorder); Carapata, febris; recurrens, louse-borne, lice; relapsing fever, Louse-borne relapsing fever, NOS
Dutch febris recurrens, overgebracht door luizen, door luizen overgebrachte febris recurrens, aandoening; Carapata, febris; recurrens, door luizen, luizen; febris recurrens, Door luizen overgebrachte febris recurrens
French Fièvre récidivante transmise par pou, Fièvre récurrente, transmise par pou
German Rueckfallfieber, von Laeusen uebertragen, von Laeusen uebertragenes Rueckfallfieber, Durch Laeuse uebertragenes Rueckfallfieber
Italian Febbre ricorrente petecchiale, Febbre ricorrente da pidocchi
Portuguese Febre recorrente transmitida por piolhos
Spanish Fiebre recurrente transmitida por piojos, fiebre recidivante por Borrelia recurrentis, fiebre recurrente por Borrelia recurrentis, fiebre recurrente transportada por piojos (trastorno), fiebre recurrente transportada por piojos, fiebre recurrente transmitida por piojos (trastorno), fiebre recurrente transmitida por piojos
Japanese シラミ媒介性回帰熱, ｼﾗﾐﾊﾞｲｶｲｾｲｶｲｷﾈﾂ
Czech Návratná horečka přenášená vší, Typhus recurrens přenášený vší
Korean 이 매개재귀열
Hungarian Visszatérő láz, tetű-által terjesztett, Tetű-által terjesztett visszatérő láz
Derived from the NIH UMLS (Unified Medical Language System)

Ontology: Borrelia recurrentis (C0315000)

Concepts Bacterium (T007)
SnomedCT 34726005
English Borrelia recurrentis (Lebert 1874) Bergey et al. 1925, Spirochaete obermeieri, Spirochaete recurrentis, Spiroschaudinnia recurrentis, Borrelia recurrentis, Borrelia novyi, Borrelia obermyeri, Borrelia recurrentis (organism)
Spanish Borrelia recurrentis (organismo), Borrelia recurrentis
Derived from the NIH UMLS (Unified Medical Language System)

Ontology: Borrelia hermsii (C0315002)

Concepts Bacterium (T007)
SnomedCT 62748005
LNC LP18295-3, MTHU005572
English Borrelia hermsii (Davis 1942) Steinhaus 1946, Spirochaeta hermsi, Borrelia hermsii (organism), Borrelia hermsii
Spanish Borrelia hermsii (organismo), Borrelia hermsii
Derived from the NIH UMLS (Unified Medical Language System)

Ontology: Borrelia turicatae (C0315017)

Concepts Bacterium (T007)
SnomedCT 24986006
English Borrelia turicatae (Brumpt 1933) Steinhaus 1946, Spirochaeta turicatae, Borrelia turicatae, Borrelia turicatae (organism)
Spanish Borrelia turicatae (organismo), Borrelia turicatae
Derived from the NIH UMLS (Unified Medical Language System)

Ontology: Borrelia miyamotoi (C1013303)

Concepts Bacterium (T007)
SnomedCT 113500001
English Borrelia miyamotonii, Borrelia miyamotonis, Borrelia miyamotoi Fukunaga et al. 1995, Borrelia miyamotoi, Borrelia miyamotoi (organism)
Spanish Borrelia miyamotoi (organismo), Borrelia miyamotoi
Derived from the NIH UMLS (Unified Medical Language System)

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