Relapsing Fever

Whether it's called bilious typhoid or tick, fowl-nest, cabin, or vagabond fever, relapsing fever is an acute infectious disease caused by a species of the Borrelia spirochetes. Relapsing fever is transmitted by lice or ticks and is characterized by relapses and remissions. This disease occurs most often in northwestern Africa, especially the highlands of Ethiopia, due to louse-born relapsing fever. Tick-borne relapsing fever is endemic to sub-Saharan Africa and is also found in the Mediterranean and Middle Eastern regions, southern Russia, the Indian subcontinent, China, and west of the Mississippi River in the United States.

The incubation period for relapsing fever is 5 to 15 days (the average is 7 days). With treatment, the prognosis for both louse- and tick-borne relapsing fever is excellent.

Untreated louse-borne fever has a high mortality risk, especially for persons in poor health, such as famine-affected populations.

Causes

Louse-borne relapsing fever (LBRF), which is transmitted by body lice, is prevalent in the developing world (Asia, Africa, and Central and South America).

Within 2 weeks of infection, affected people develop sudden-onset high fever. In louse-borne relapsing fever, the initial episode usually lasts 3-6 days and is usually followed by a single, milder episode. In tick-borne relapsing fever, multiple episodes of fever occur and each may last up to 3 days. Individuals may be free of fever for up to 2 weeks prior to a relapse.

In both forms, the fever episode may end in 'crisis,' which consists of shaking chills, followed by intense sweating, falling temperature, and low blood pressure -- this stage may result in death in up to 10% of individuals.

Symptoms and Signs

• Sudden onset of high fever
• Headache; neck stiffness
• Nausea
• Vomiting
• Muscle aches (myalgia)
• Joint aches (arthralgia)
• Bleeding
• Seizures
• Unsteady gait
• Coma
• weakness

Diagnostic tests

Blood smears done with Wright's or Giemsa stain may confirm the diagnosis by revealing the infecting spirochete if blood is obtained during a febrile period. Borrelia spirochetes may be less detectable in subsequent relapses because their number in the blood declines.

In such cases, a sample of the patient's blood or tissue may be injected into a young rat and incubated there for 1 to 10 days. If the patient has relapsing fever, subsequent testing of the rat's tail blood may disclose large numbers of spirochetes.

Urine and cerebrospinal fluid analyses may uncover spirochete-induced infection. Other abnormal findings include a white blood cell (WBC) count as high as 25,OOO/mm3, with increases in lymphocyte levels and erythrocyte sedimentation rate. However, the WBC count may be within normal limits. Because the Borrelia organism is a spirochete, test findings in relapsing fever may be similar to those in syphilis.

Treatment

Treatment with erythromycin, tetracycline, chloramphenicol, or penicillin results in clearance of the spirochetes and a remission of symptoms. In children under age 9 and pregnant women, erythromycin and penicillin are preferred. Hydrocortisone and acetaminophen given at the same time as antibiotics reduce peak body temperature. Vitamin K and other soluble vitamins may help counter deficiencies in louse-type induced fever.

An adult usually receives oral antibiotic therapy ­tetracycline for 4 to 5 days - as the first choice. In children and seriously ill patients who can't take tetracycline, penicillin G, erythromycin, or ceftriaxone may be administered as an alternative.

Antibiotics given at the height of a severe febrile attack can result in a Jarisch-Herxheimer reaction, causing malaise, rigor, leukopenia, flushing, fever, tachycardia, increasing respiratory rate, and hypotension. This reaction, which is caused by toxic by­products from massive spirochete destruction, can mimic septic shock and may be fatal.

Prevention

Wearing proper clothing and insect repellent will help prevent infection. Lice and tick control in endemic areas is another important public health measure.

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