Relapsing fever, also known as typhinia,^[1] is an infection caused by certain bacteria in the genus Borrelia.^[2] It is a vector-borne disease transmitted through the bites of lice or soft-bodied ticks.^[3]

Infection [link]

Louse-borne relapsing fever [link]

Along with Rickettsia prowazekii and Bartonella quintana, Borrelia recurrentis is one of three pathogens of which the body louse (Pediculus humanus humanus) is a vector.^[4] Louse-borne relapsing fever is more severe than the tick-borne variety.^{[citation needed]}

Louse-borne relapsing fever occurs in epidemics amid poor living conditions, famine and war in the developing world.^[5] It is currently prevalent in Ethiopia and Sudan.

Mortality rate is 1% with treatment and 30-70% without treatment. Poor prognostic signs include severe jaundice, severe change in mental status, severe bleeding and a prolonged QT interval on ECG.

Lice that feed on infected humans acquire the Borrelia organisms that then multiply in the gut of the louse. When an infected louse feeds on an uninfected human, the organism gains access when the victim crushes the louse or scratches the area where the louse is feeding. B. recurrentis infects the person via mucous membranes and then invades the bloodstream. No animal reservoir exists.

Tick-borne relapsing fever [link]

Tick-borne relapsing fever is found primarily in Africa, Spain, Saudi Arabia, Asia in and certain areas of Canada and the western United States.

Other relapsing infections are acquired from other Borrelia species, which can be spread from rodents, and serve as a reservoir for the infection, via a tick vector.

• Borrelia hermsii
• Borrelia parkeri
• Borrelia duttoni, transmitted by the soft-bodied African tick Ornithodoros moubata, is responsible for the relapsing fever found in central, eastern and southern Africa.
• Borrelia miyamotoi ^[6]

Borrelia hermsii and Borrelia recurrentis cause very similar diseases. However, one or two relapses are common with the disease associated with Borrelia hermsii which is also the most common cause of relapsing disease in the United States. (Three or four relapses are common with the disease caused by B. recurrentis. B. recurrentis has longer febrile and afebrile intervals and a longer incubation period than Borrelia hermsii.)

Diagnosis [link]

Most people who are infected develop sickness between 5 and 15 days after they are bitten. The symptoms may include a sudden fever, chills, headaches, muscle or joint aches and nausea. A rash may also occur. These symptoms usually continue for between 2 to 9 days, then disappear. This cycle may continue for several weeks if the person is not treated.^[7] Relapsing fever is easily treated with a one-to-two week course of antibiotics and most people improve within 24 hours commencement. Complications and death due to relapsing fever are rare.

Relapsing fever is a candidate etiology for a mysterious series of plagues in late-medieval and early-renaissance England. At the time, they were called sweating sicknesses. They have not recurred in epidemic form since the 16th century.

Treatment [link]

Tetracycline-class antibiotics are most effective. These can, however, induce a Jarisch-Herxheimer reaction in over half those treated, producing anxiety, diaphoresis, fever, tachycardia and tachypnea with an initial pressor response followed rapidly by hypotension. Recent studies have shown that tumor necrosis factor-alpha (TNF-alpha) may be partly responsible for this reaction.

See also [link]

• Lyme disease
• Typhus

References [link]

External links [link]

• Relapsing+fever at eMedicine Dictionary
• CDC: Relapsing Fever
• Scientist and astronomer Larry Webster infected with relapsing fever