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Key Features

  • Infectious organisms are spirochetes of the genus Borrelia

  • In the United States, infected ticks are found throughout the west, especially in mountainous areas

  • Human clinical cases are uncommon, however, large epidemics may occur

  • Both tick-borne and louse-borne disease occur

  • Tick-borne disease

    • Main reservoir is rodents, which serve as the source of infection for ticks

    • Not transmitted from person to person

  • Louse-borne disease: lice transmit Borrelia from an infected person

Clinical Findings

  • Abrupt onset of fever, chills, tachycardia, nausea and vomiting, arthralgia, and severe headache

  • Hepatomegaly and splenomegaly, rashes

  • Delirium, neurologic and psychological abnormalities

  • The attack terminates, usually abruptly, after 3–10 days

  • After an interval of 1–2 weeks, relapse occurs, and 3–10 relapses may occur before recovery

  • Three to 10 relapses may occur before recovery in tick-borne disease, whereas louse-borne disease is associated with only 1 or 2 relapses

Diagnosis

  • During fever, large spirochetes are seen in thick and thin blood smears stained with Wright or Giemsa stain

  • Organisms can be cultured in special media but rapidly lose pathogenicity

  • Anti-Borrelia antibodies develop during the illness

  • The Weil-Felix test for rickettsioses, nontreponemal serologic tests for syphilis, and indirect fluorescent antibody and Western blot tests for Borrelia burgdorferi may be falsely positive

  • Polymerase chain reaction (PCR) assays have been developed but are not widely available

  • Cerebrospinal fluid abnormalities occur in patients with meningeal involvement

  • Mild anemia and thrombocytopenia are common but white blood cell count tends to be normal

  • Differential diagnosis

    • Malaria

    • Leptospirosis

    • Meningococcemia

    • Yellow fever

    • Typhus

    • Rat-bite fever

Treatment

  • Tick-borne relapsing fever: tetracycline or erythromycin, 0.5 g orally four times daily for 10 days

  • Louse-borne relapsing fever: tetracycline or erythromycin, 0.5 g orally once, or procaine penicillin G, 600,000–800,000 units intramuscularly once

  • If CNS invasion is suspected,

    • Penicillin G, 3 million units intravenously every 4 hours for 10–14 days or

    • Ceftriaxone, 1 g intravenously daily for 10–14 days

  • Jarisch-Herxheimer reactions

    • Occur commonly and may be life-threatening

    • Administration of anti-TNF antibodies prior to antibiotic therapy can be effective in preventing these reactions

  • With treatment, the initial attack is shortened and relapses are largely prevented

  • Overall mortality rate is ~5%

  • Fatalities most common in old, debilitated, or very young patients

  • Prevention of relapsing fever is by prevention of tick bites and delousing procedures

  • To prevent recurrent fever following a tick bite in highly endemic areas, give doxycycline 200 mg on day 1 and 100 mg/day for 4 days

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