Borrelia recurrentis causes louse-borne relapsing fever (LBRF) and is transmitted from person to person by the body louse. Spirochetes are introduced not from the bite itself but from rubbing of the insect's feces into the bite site in response to irritation. Tick-borne relapsing fever (TBRF), a zoonosis usually transmitted via the bite of various Ornithodoros ticks, is caused by multiple Borrelia species. B. miyamotoi can cause relapsing fever but is transmitted to humans from other mammals by hard ticks (e.g., Ixodes scapularis) that also transmit B. burgdorferi and other tick-borne illnesses.
LBRF transmission is currently limited to Ethiopia and adjacent countries, with epidemics occurring during famine, natural disaster, and war. TBRF occurs worldwide, with Africa most affected. In North America, most cases of TBRF are due to B. hermsii and B. turicatae and occur in the western United States and Canada.
- Both TBRF and LBRF present with a sudden onset of discrete febrile periods separated by afebrile periods of a few days.
- In LBRF, the first episode of fever persists for 3-6 days and is followed by a single milder episode.
- In TBRF, multiple febrile periods last 1-3 days each.
- In both forms, the duration of an afebrile period ranges from 4 to 14 days.
- In addition to fever, pts commonly develop headaches, myalgias, nausea, abdominal pain (due to hepatosplenomegaly), and arthralgias.
- Petechiae, ecchymoses, and epistaxis are common in LBRF but not in TBRF.
- Localizing neurologic findings (e.g., Bell's palsy, deafness, visual impairment) are more common in TBRF.
In pts with a compatible history (i.e., a characteristic fever pattern and exposure to body lice, soft-bodied ticks, or Ixodes hard-bodied ticks in at-risk geographic regions 1-2 weeks prior to illness onset), laboratory confirmation is made by the detection or isolation of spirochetes from blood during a febrile episode. Microscopic examination of Wright- or Giemsa-stained thin blood smears usually yields positive results if the concentration of spirochetes is ≥105 /mL.
- PCR techniques may reveal spirochetes between febrile episodes.
- Serologic confirmation of infection is limited by false-positive results and poor sensitivity.
| TREATMENT | ||
Relapsing Fever
|