An infection transmitted by a louse or tick which is characterized by repeated episodes of fever .

Causes, incidence, and risk factors

Relapsing fever is an infection caused by bacteria in the Borrelia family, and has two major forms. Tick-borne relapsing fever is transmitted by the Ornithodoros tick and occurs in Africa, Spain, Saudi Arabia, Asia and certain areas in the western US and Canada. Louse-borne relapsing fever (transmitted by body lice ) is prevalent in the developing world (Asia, Africa, and Central and South America). Within 2 weeks of infection, individuals develop the sudden onset of high fever. In louse-borne relapsing fever, the initial episode usually lasts 3 to 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 3 days. Individuals may be free of fever for up to 2 weeks prior to a repeated episode of fever. In both forms, the fever episode may end by 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. Some individuals after several cycles of fever may develop dramatic central nervous system signs such as seizures , stupor and coma. The Borrelia organism may also invade heart and liver tissues causing inflammation of the heart muscle ( myocarditis ) and inflammation of the liver ( hepatitis ). Diffuse bleeding and pneumonia are other complications of this illness.

Signs and tests

The diagnosis of relapsing fever should be suspected in a returning traveler or in an individual from an endemic area who presents with repeated episodes of fever, in particular if followed by the crisis stage, and if a history of exposure to lice or soft-bodied ticks is given. A blood smear is frequently obtained to attempt direct visualization of the organism. Culture is not widely available in most laboratories. Selected blood antibody tests are sometimes used.

Treatment

The mainstay of treatment involves antibiotics -- primarily tetracyclines.

Expectations (prognosis)

The mortality rates of untreated louse-borne relapsing fever range from 10-70%; and 4-10% in tick-borne relapsing fever. With early treatment, the mortality rate is decreased to 2-5%. Individuals with coma at the time of presentation, myocarditis, liver dysfunction, and pneumonia are at higher risk of death.

Complications

Calling your health care provider

Notify your medical provider if you are a returning traveler and you develop fever -- there are many different possible infections that will need to be investigated in a timely manner.

Prevention

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