Relapsing Fever

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

• Differential diagnosis

  • Malaria

  • Leptospirosis

  • Meningococcemia

  • Yellow fever

  • Typhus

  • Rat-bite fever

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

Treatment

• Tick-borne relapsing fever

  • Tetracycline or erythromycin, 0.5 g orally four times daily for 10 days

  • In severe cases, penicillin G, 3 million units intravenously every 4 hours, or ceftriaxone, 1 g intravenously daily

• 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, intravenous penicillin G or ceftriaxone should be continued 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