Relapsing Fever

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

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

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 can be performed on blood, CSF and tissue but are not always available in endemic regions

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

Tick-borne relapsing fever

• Treatment begins with penicillin G, 3 million units intravenously every 4 hours, or ceftriaxone, 1 g intravenously daily

• With clinical improvement, a 10-day course can be completed with 0.5 g of tetracycline or erythromycin given orally four times daily

• All pregnant women with tick-borne disease should be treated for 14 days, ideally with intravenous penicillin or ceftriaxone

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