Tick-borne relapsing fever: Difference between revisions

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* '''Tick-borne relapsing fever''' (TBRF) is caused by a number of non-Lyme ''Borrelia'' species
*'''Tick-borne relapsing fever''' (TBRF) is caused by a number of non-Lyme ''Borrelia'' species


== Background ==
==Background==
=== Microbiology ===
===Microbiology===

* Tick-borne relapsing fever is caused by multiple non-Lyme ''Borrelia'' species with global distribution, usually carried by [[Ornithodorus species]] ticks
* Other non-Lyme ''Borrelia'' species include ''B. miyamotoi'' and ''B. lonestari'', although ''B. lonestari'' may also be able to cause TBRF
*Tick-borne relapsing fever is caused by multiple non-Lyme ''Borrelia'' species with global distribution, usually carried by [[Ornithodorus species]] ticks
*Other non-Lyme ''Borrelia'' species include ''B. miyamotoi'' and ''B. lonestari'', although ''B. lonestari'' may also be able to cause TBRF
* ''Borrelia'' are spirochetes
*''Borrelia'' are [[Cellular shape::spirochete|spirochetes]]
* Serotypes are determined by the outer membrane variable major proteins (vmp)
*Serotypes are determined by the outer membrane variable major proteins (vmp)
* Grow in modified Kelly medium and stained by Wright stain (in peripheral blood film)
*Grow in modified Kelly medium and stained by Wright stain (in peripheral blood film)


{| class="wikitable"
{| class="wikitable"
! Species !! Vector !! Distribution !! Reservoir
!Species!!Vector!!Distribution!!Reservoir
|-
|-
| ''B. hermsii'' || ''O. hermsii'' || Western US and Canada (most common) || Rodent
|''[[Borrelia hermsii|B. hermsii]]''||''O. hermsii''||Western US and Canada (most common)||Rodent
|-
|-
| ''B. turicatae'' || ''O. turicata'' || Southwestern US || Rodent
|''[[Borrelia turicatae|B. turicatae]]''||''O. turicata''||Southwestern US||Rodent
|-
|-
| ''B. parkeri'' || ''O. parkeri'' || Western US and Baja California || Rodent
|''[[Borrelia parkeri|B. parkeri]]''||''O. parkeri''||Western US and Baja California||Rodent
|-
|-
| ''B. mazzottii'' || ''O. talaje'' || Mexico and Central America || Rodent
|''[[Borrelia mazzottii|B. mazzottii]]''||''O. talaje''||Mexico and Central America||Rodent
|-
|-
| ''B. venezuelensis'' || ''O. rudis'' || South America || Rodent
|''[[Borrelia venezuelensis|B. venezuelensis]]''||''O. rudis''||South America||Rodent
|-
|-
| ''B. crocidurae'' || ''O. erraticus'' || Middle East || Rodent
|''[[Borrelia crocidurae|B. crocidurae]]''||''O. erraticus''||Middle East||Rodent
|-
|-
| ''B. hispanica'' || ''O. marocanus'' || Iberian peninsula and North Africa ||
|''[[Borrelia hispanica|B. hispanica]]''||''O. marocanus''||Iberian peninsula and North Africa||
|}
|}


=== Epidemiology ===
===Epidemiology===

* TBRF is transmitted by [[Ornithodoros species]] ticks, with rodent reservoirs
*TBRF is transmitted by [[Vector::Ornithodoros species]] ticks, with rodent reservoirs
* Present on every continent except Australia and Antarctica
*Present on every continent except Australia and Antarctica
* In North America, it is mostly in the Rocky Mountain regions above 1500 feet elevation
*In North America, it is mostly in the Rocky Mountain regions above 1500 feet elevation
** Most have exposure to woodpiles or cabins with rodents
**Most have exposure to woodpiles or cabins with rodents
* Spirochetes can survive in the tick for years, and can be transmitted vertically within ticks
*Spirochetes can survive in the tick for years, and can be transmitted vertically within ticks
** Doesn't need its mammalian host to complete its life cycle
**Doesn't need its mammalian host to complete its life cycle
* Ticks feed for short periods (20 min) and are painless, so is often not noticed
*Ticks feed for short periods (20 min) and are painless, so is often not noticed
* Can be transmitted vertically, by transfusion, and from laboratory exposure
*Can be transmitted vertically, by transfusion, and from laboratory exposure

===Pathophysiology===

*During febrile periods, spirochetes divide rapidly and cause a spirochetemia
*This is followed by an immune response to the vmp proteins, which clears the spirochetemia and the patient becomes afebrile
*The vmp proteins undergo rearrangement, evading the immune system and allowing another spirochetemia
**This is the cause of the relapsing fever

==Clinical Presentation==

*Incubation period of 7 days (range 2 to 18 days)
*Relapsing fevers: febrile for 3 days, afebrile for 7 days
*TBRF can relapse up to 30 times, whereas LBRF is usually self-limited after a single relapse
**Febrile periods may be associated with headache, myalgia, arthralgia, dizziness, and vomiting
**Each relapse is usually less severe
*Some patients will have lymphadenopathy, hepatosplenomegaly, and a rash
*Rare complications include lymphocytic meningitis, Bell palsy and other cranial nerve palsies, paralysis, seizure, uveitis, endophthalmitis, ARDS, and myocarditis
*Can cause spontaneous abortion in pregnant women
*May be septic, with multiple organ involvement
*May have a Jarisch-Herxheimer reaction following empiric antibiotics

==Differential Diagnosis==

*[[Colorado tick fever]] (Coltivirus)
*[[Brucellosis]]
*[[Tularemia]]
*Juvenile rheumatoid arthritis
*[[Leptospirosis]]
*Occult malignancy
*[[Lyme disease]]


==Diagnosis==
=== Pathophysiology ===
* During febrile periods, spirochetes divide rapidly and cause a spirochetemia
* This is followed by an immune response to the vmp proteins, which clears the spirochetemia and the patient becomes afebrile
* The vmp proteins undergo rearrangement, evading the immune system and allowing another spirochetemia
** This is the cause of the relapsing fever


*Often seen on blood film
== Clinical Presentation ==
**Giemsa or Wright stains
* Incubation period of 7 days (range 2 to 18 days)
* Relapsing fevers: febrile for 3 days, afebrile for 7 days
**70% sensitive during febrile period for TBRF, lower for LBRF
*Acute-convalescent serology with IFA/EIA
* TBRF can relapse up to 30 times, whereas LBRF is usually self-limited after a single relapse
**May cross-react with Lyme disease
** Febrile periods may be associated with headache, myalgia, arthralgia, dizziness, and vomiting
*Can cause a false-positive VDRL
** Each relapse is usually less severe
*Can be cultured with modified Kelly medium
* Some patients will have lymphadenopathy, hepatosplenomegaly, and a rash
* Rare complications include lymphocytic meningitis, Bell palsy and other cranial nerve palsies, paralysis, seizure, uveitis, endophthalmitis, ARDS, and myocarditis
* Can cause spontaneous abortion in pregnant women
* May be septic, with multiple organ involvement
* May have a Jarisch-Herxheimer reaction following empiric antibiotics


==Management==
== Differential Diagnosis ==
===Tick-borne relapsing fever===
* [[Colorado tick fever]] (Coltivirus)
* [[Brucellosis]]
* [[Tularemia]]
* Juvenile rheumatoid arthritis
* [[Leptospirosis]]
* Occult malignancy
* [[Lyme disease]]


*First-line: [[Is treated by::doxycycline]] 100 mg po bid for 7 to 10 days
== Diagnosis ==
*Alternatives: [[Is treated by::erythromycin]] 500 mg qid for 10 days
* Often seen on blood film
*If CNS involvement:
** Giemsa or Wright stains
**[[Is treated by::Penicillin]] G 3 mU IV q4h for 10-14 days, or
** 70% sensitive during febrile period for TBRF, lower for LBRF
**[[Is treated by::Ceftriaxone]] 2 g IV q24h for 10-14 days
* Acute-convalescent serology with IFA/EIA
** May cross-react with Lyme disease
* Can cause a false-positive VDRL
* Can be cultured with modified Kelly medium


== Management ==
==Prevention==
=== Tick-borne relapsing fever ===
* First-line: [[Is treated by::doxycycline]] 100 mg po bid for 7 to 10 days
* Alternatives: [[Is treated by::erythromycin]] 500 mg qid for 10 days
* If CNS involvement:
** [[Is treated by::Penicillin]] G 3 mU IV q4h for 10-14 days, or
** [[Is treated by::Ceftriaxone]] 2 g IV q24h for 10-14 days


*Can do post-exposure prophylaxis with [[doxycycline]] 200 mg po once followed by 100 mg daily for 4 days
== Prevention ==
* Can do post-exposure prophylaxis with [[doxycycline]] 200 mg po once followed by 100 mg daily for 4 days


[[Category:Borrelioses]]
[[Category:Borrelioses]]

Revision as of 12:10, 2 August 2020

  • Tick-borne relapsing fever (TBRF) is caused by a number of non-Lyme Borrelia species

Background

Microbiology

  • Tick-borne relapsing fever is caused by multiple non-Lyme Borrelia species with global distribution, usually carried by Ornithodorus species ticks
  • Other non-Lyme Borrelia species include B. miyamotoi and B. lonestari, although B. lonestari may also be able to cause TBRF
  • Borrelia are spirochetes
  • Serotypes are determined by the outer membrane variable major proteins (vmp)
  • Grow in modified Kelly medium and stained by Wright stain (in peripheral blood film)
Species Vector Distribution Reservoir
B. hermsii O. hermsii Western US and Canada (most common) Rodent
B. turicatae O. turicata Southwestern US Rodent
B. parkeri O. parkeri Western US and Baja California Rodent
B. mazzottii O. talaje Mexico and Central America Rodent
B. venezuelensis O. rudis South America Rodent
B. crocidurae O. erraticus Middle East Rodent
B. hispanica O. marocanus Iberian peninsula and North Africa

Epidemiology

  • TBRF is transmitted by Ornithodoros species ticks, with rodent reservoirs
  • Present on every continent except Australia and Antarctica
  • In North America, it is mostly in the Rocky Mountain regions above 1500 feet elevation
    • Most have exposure to woodpiles or cabins with rodents
  • Spirochetes can survive in the tick for years, and can be transmitted vertically within ticks
    • Doesn't need its mammalian host to complete its life cycle
  • Ticks feed for short periods (20 min) and are painless, so is often not noticed
  • Can be transmitted vertically, by transfusion, and from laboratory exposure

Pathophysiology

  • During febrile periods, spirochetes divide rapidly and cause a spirochetemia
  • This is followed by an immune response to the vmp proteins, which clears the spirochetemia and the patient becomes afebrile
  • The vmp proteins undergo rearrangement, evading the immune system and allowing another spirochetemia
    • This is the cause of the relapsing fever

Clinical Presentation

  • Incubation period of 7 days (range 2 to 18 days)
  • Relapsing fevers: febrile for 3 days, afebrile for 7 days
  • TBRF can relapse up to 30 times, whereas LBRF is usually self-limited after a single relapse
    • Febrile periods may be associated with headache, myalgia, arthralgia, dizziness, and vomiting
    • Each relapse is usually less severe
  • Some patients will have lymphadenopathy, hepatosplenomegaly, and a rash
  • Rare complications include lymphocytic meningitis, Bell palsy and other cranial nerve palsies, paralysis, seizure, uveitis, endophthalmitis, ARDS, and myocarditis
  • Can cause spontaneous abortion in pregnant women
  • May be septic, with multiple organ involvement
  • May have a Jarisch-Herxheimer reaction following empiric antibiotics

Differential Diagnosis

Diagnosis

  • Often seen on blood film
    • Giemsa or Wright stains
    • 70% sensitive during febrile period for TBRF, lower for LBRF
  • Acute-convalescent serology with IFA/EIA
    • May cross-react with Lyme disease
  • Can cause a false-positive VDRL
  • Can be cultured with modified Kelly medium

Management

Tick-borne relapsing fever

Prevention

  • Can do post-exposure prophylaxis with doxycycline 200 mg po once followed by 100 mg daily for 4 days
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