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 louseborne 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

The body louse (Pediculus humanus corporis) carries spirochete responsible for relapsing fever (B. recurrentis). This louse transmits the disease from person to person. Inoculation occurs when the victim crushes louse, causing its infected blood or body fluid to seep into the victim's broken skin or mucous membranes. Louse-borne relapsing fever typically erupts epidemically during wars, famines, and mass migrations. Cold weather and crowded living conditions favor the spread of body lice.

Tick-borne relapsing fever is caused by several species of Borrelia transmitted to humans by Ornithodoros ticks. Outbreaks usually occur during the summer when ticks and their hosts (chipmunks, goats, prairie dogs) are most active. Cold-weather outbreaks may afflict people who sleep in tick-infested cabins, such as campers. Because tick bites are painless and Ornithodoros ticks frequently feed at night without imbedding themselves in the victim's skin, many people are bitten unknowingly.

Symptoms

The disease causes a fever which lasts from 2-9 days and alternates with a period of 2-4 days without fever, after which fever returns. The number of relapses varies from 1-10 or more. The first onset of fever is often accompanied by a rash. Relapsing fever can be fatal if not treated.

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.

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

• Avoid tick infested areas, especially during the warmer months.
• Wear light colored clothing so ticks can be easily seen. Wear a long sleeved shirt, hat, long pants, and tuck your pant legs into your socks.
• Walk in the center of trails to avoid overhanging grass and brush.
• Remove attached ticks immediately.