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Relapsing Fever

Relapsing Fever


Relapsing fever refers to two similar illnesses, both of which cause high fevers. The fevers resolve, only to recur again within about a week.


Relapsing fever is caused by spiral-shaped bacteria of the genus Borrelia. This bacterium lives in rodents and in insects, specifically ticks and body lice. The form of relapsing fever acquired from ticks is slightly different from that acquired from body lice.

In tick-borne relapsing fever (TBRF), rodents (rats, mice, chipmunks, and squirrels) which carry Borrelia are fed upon by ticks. The ticks then acquire the bacteria, and are able to pass it on to humans. TBRF is most common in sub-Saharan Africa, parts of the Mediterranean, areas in the Middle East, India, China, and the south of Russia. Also, Borrelia causing TBRF exist in the western regions of the United States, particularly in mountainous areas. The disease is said to be endemic to these areas, meaning that the causative agents occur naturally and consistently within these locations.

In louse-borne relapsing fever (LBRF), lice acquire Borrelia from humans who are already infected. These lice can then go on to infect other humans. LBRF is said to be epidemic, as opposed to endemic, meaning that it can occur suddenly in large numbers in specific communities of people. LBRF occurs in places where poverty and overcrowding predispose to human infestation with lice. LBRF has flared during wars, when conditions are crowded and good hygiene is next to impossible. At this time, LBRF is found in areas of east and central Africa, China, and in the Andes Mountains of Peru.

Causes and symptoms

In TBRF, humans contract Borrelia when they are fed upon by ticks. Ticks often feed on humans at night, so many people who have been bitten are unaware that they have been. The bacteria is passed on to humans through the infected body fluids of the tick.

In LBRF, a louse must be crushed or smashed in order for Borrelia to be released. The bacteria then enter the human body through areas where the person may have scratched him or herself.

Both types of relapsing fever occur some days after having acquired the bacteria. About a week after becoming infected, symptoms begin. The patient spikes a very high fever, with chills, sweating, terrible headache, nausea, vomiting, severe pain in the muscles and joints, and extreme weakness. The patient may become dizzy and confused. The eyes may be bloodshot and very sensitive to light. A cough may develop. The heart rate is greatly increased, and the liver and spleen may be swollen. Because the substances responsible for blood clotting may be disturbed during the illness, tiny purple marks may appear on the skin, which are evidence of minor bleeding occurring under the skin. The patient may suffer from a nosebleed, or may cough up bloody sputum. All of these symptoms last for about three days in TBRF, and about five days in LBRF.

With or without treatment, a crisis may occur as the bacteria are cleared from the blood. This crisis, called a Jarisch-Herxheimer reaction, results in a new spike in fever, chills, and an initial rise in blood pressure. The blood pressure then falls drastically, which may deprive tissues and organs of appropriate blood flow (shock ). This reaction usually lasts for about a day.

Recurrent episodes of fever with less severe symptoms occur after about a week. In untreated infections, fevers recur about three times in TBRF, and only once or twice in LBRF.


Diagnosis of relapsing fever is relatively easy, because the causative bacteria can be found by examining a sample of blood under the microscope. The characteristically spiral-shaped bacteria are easily identifiable. The blood is best drawn during the period of high fever, because the bacteria are present in the blood in great numbers at that time.


Either tetracycline or erythromycin is effective against both forms of relapsing fever. The medications are given for about a week for cases of TBRF; LBRF requires only a single dose. Children and pregnant women should receive either erythromycin or penicillin. Because of the risk of the Jarish-Herxheimer reaction, patients must be very carefully monitored during the initial administration of antibiotic medications. Solutions containing salts must be given through a needle in the vein (intravenously) to keep the blood pressure from dropping too drastically. Patients with extreme reactions may need medications to improve blood circulation until the reaction resolves.


In epidemics of LBRF, death rates among untreated victims have run as high as 30%. With treatment, and careful monitoring for the development of the Jarish-Herxheimer reaction, prognosis is good for both LBRF and TBRF.


Prevention of TBRF requires rodent control, especially in and near homes. Careful use of insecticides on skin and clothing is important for people who may be enjoying outdoor recreation in areas known to harbor the disease-carrying ticks.

Prevention of LBRF is possible, but probably more difficult. Good hygiene and decent living conditions would prevent the spread of LBRF, but these may be difficult for those people most at risk for the disease.


Endemic Refers to a particular organism which consistently exists in a particular location under normal conditions.

Epidemic Refers to a condition suddenly acquired by a large number of people within a specific community, and which spreads rapidly throughout that community.

Shock A state in which the blood pressure is so low that organs and tissues are not receiving an appropriate flow of blood.



Centers for Disease Control and Prevention. 1600 Clifton Rd., NE, Atlanta, GA 30333. (800) 311-3435, (404) 639-3311.

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Relapsing Fever


Relapsing fever is an acute relapsing systemic illness caused by infection with spirochetal bacteria in the genus Borrelia. Louse-borne (epidemic) relapsing fever (LBRF) is caused by Borrelia recurrentis, and tick-borne (endemic) relapsing fever (TBRF) by several closely related species of Borrelia. Louse-borne relapsing fever is transmitted by the human body louse, Pediculus humanus ; TBRF is transmitted by the bite of various soft-bodied ticks of the genus Ornithodorus. LBRF has, for the past several decades, been reported only in Ethiopia and several surrounding countries. It especially affects populations that are crowded, impoverished, and displaced by war or famineall factors associated with poor hygiene and lice infestation. TBRF occurs in scattered temperate and tropical areas worldwide; in the United States it occurs almost exclusively in the western states, especially in forested, mountainous areas. TBRF typically occurs in small, often familial, clusters, and it is associated with sleeping in rodent- and tick-infested homes or cabins.

Following a usual incubation period of four to seven days, illness begins with the abrupt onset of fever, aches and pains in muscles and joints, headache, shaking chills, sweats, loss of appetite, weakness, and prostration. Periods of fever usually last for several days, typically ending with a crisis characterized by rigors and rising temperature, followed by an abrupt fall in temperature, profuse sweating, and hypotension. Untreated, relapses may recur after intervals of several days to a week or more. An average of three, and as many as ten, relapses may occur in TBRF, while only one to three relapses occur in LBRF. Relapses are associated with antigenic changes in bacterial outer-surface proteins.

The diagnosis of borrelial fevers is made by eliciting a history of possible infective exposure, by the typical relapsing character of the illness, and by identifying borreliae in the patient's blood. Relapsing fever is readily cured with any of several antibioticstetracyclines, erythromycin, and chloramphenicol are recommended choices. Control and prevention of LBRF relies on basic sanitation and hygiene to prevent or rid clothing and bedclothes of body lice, early case detection, and treatment. TBRF is prevented by removing rodent nests from buildings, rodent-proofing homes and cabins, and treating suspected tick harborage with chemical acaricides.

David T. Dennis

(see also: Communicable Disease Control; Environmental Determinants of Health; Vector-Borne Diseases )


Anonymous (2000). "Relapsing Fever." In Control of Communicable Diseases Manual, 17th edition, ed. I. Chin. Washington, DC: American Public Health Association.

Dworkin, M. S. et al. (1998). "Tick-Borne Relapsing Fever in the Northwestern United States and Southwestern Canada." Clinical Infectious Diseases 26: 122131.

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relapsing fever

relapsing fever (ri-laps-ing) n. an infectious disease caused by bacteria of the genus Borrelia, which is transmitted by ticks or lice and results in recurrent fever. The first episode of fever is accompanied by severe headache and aching muscles and joints. Subsequent attacks are milder and occur at intervals of 3–10 days.

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