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Disease Name: Relapsing fever

Quick Links

Please review the Idaho Reportable Disease Rules (IDAPA 16.02.10) for the most up-to-date information.

Tick-borne Relapsing Fever (TBRF): http://www.cdc.gov/relapsing-fever/index.html

Louse-borne Relapsing Fever (LBRF): http://www.cdc.gov/relapsing-fever/resources/louse.html

Overview / Case Definition

Relapsing fever is bacterial infection characterized by recurring episodes of fever, headache, muscle and joint aches, and nausea. It is caused by certain species of Borrelia spirochetes. There are two types of relapsing fever:

Tick-borne relapsing fever (TBRF)

Tick-borne relapsing fever occurs in the western United States and is usually linked to sleeping in rustic, rodent-infested cabins in mountainous areas.

Louse-borne relapsing fever (LBRF)

Louse-borne relapsing fever is caused by a spiral-shaped bacteria, Borrelia recurrentis, which is transmitted from human to human by the body louse. LBRF is generally restricted to refugee settings in developing regions of the world.

 LBRF outbreaks most commonly occur in conditions of overcrowding and social disruption. LBRF epidemics occurred frequently in Europe during the early 20th Century. Between 1919 and 1923, 13 million cases resulting in 5 million deaths occurred in the social upheaval that overtook Russia and eastern Europe. During World War II, a million cases occurred in North Africa. Today, LBRF causes sporadic illness and outbreaks in sub-Saharan Africa, particularly in regions affected by war and in refugee camps. LBRF is commonly found in Ethiopia, Sudan, Eritrea, and Somalia. Illness can be severe, with mortality of 30 to 70% in outbreaks.




Within 3 working days

Reportable by Healthcare and Labs:

Reportable by Food Service Facility:

Suspect Reportable:

Reporting Timeframe: Within 3 working days

Diagnosis / Testing

Tick-borne relapsing fever (TBRF)

Spirochetemia (spirochetes in blood) in TBRF often reaches high concentrations, 100-1000 times more than in cases of early Lyme disease. Thus, microscopy is a useful diagnostic tool for TBRF. The definitive diagnosis of TBRF may be based on the observation of relapsing fever spirochetes (Borrelia hermsii, B. turicatae, or B. parkerii in the US) in peripheral blood smears of a symptomatic person by a microscopist trained in spirochete identification. Although best visualized by dark field microscopy, the organisms can also be detected using Wright-Giemsa or acridine orange stains.

Peripheral blood smear. The TBRF bacteria are long and spiral-shaped. The circular objects are red blood cells. The irregular purple object in the top right corner is a white blood cell. The organisms are best detected in blood obtained while a person is febrile. With subsequent febrile episodes, the number of circulating spirochetes decreases, making it harder to detect spirochetes on a peripheral blood smear. Even during the initial episode spirochetes will only be seen 70% of the time. Blood samples obtained before antibiotic treatment can be cultured using BSK (Barbour Stoner Kelly) medium or by inoculating immature mice. The spirochete will usually be evident within 24 hours if the blood was drawn during a febrile episode.

Although not valuable for making an immediate diagnosis, serologic testing is available through public health laboratories and some private laboratories. Acute serum should be taken within 7 days of symptom onset and convalescent serum should be taken at least 21 days after symptoms start. Early antibiotic treatment may blunt the antibody response and the antibody levels may wane quickly during the months after exposure.

Louse-borne relapsing fever (LBRF)

Spirochetes can be observed by dark-field microscopy and in Wright-, Giemsa, or acridine orange-stained preparations of thin or dehemoglobinized thick smears of peripheral blood or in stained buffy-coat preparations. Organisms often can be visualized in blood obtained while the person is febrile, particularly during initial febrile episodes; organisms are less likely to be recovered from subsequent relapses. Spirochetes can be cultured rom blood in Barbour-Stoenner-Kelly medium or by intraperitoneal inoculation of immature laboratory mice, although these tests are not widely available. Serum antibodies to Borrelia species can be detected by enzyme immunoassay and Western immunoblot analysis at some reference and commercial specialty laboratories; a fourfold increase in titer is considered confirmatory. These antibody tests are not standardized and are affected by antigenic variations among and within Borrelia species and strains. Serologic cross-reactions occur with other spirochetes, including Borrelia burgdorferi, Treponema pallidum, and Leptospira species.


Additional Information

Tick-borne Relapsing Fever (TBRF): http://www.cdc.gov/relapsing-fever/index.html

Louse-borne Relapsing Fever (LBRF): http://www.cdc.gov/relapsing-fever/resources/louse.html

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