What is Tick-borne Relapsing Fever (TBRF)?

Relapsing fever is caused by spiral-shaped bacteria of the genus Borrelia and sub-species Relapsing Fever Borrelia (RFB). They are closely related to B. burgdorferi, the causative agent of Lyme disease. This group of bacteria is found world-wide and are transmitted by the body louse and ticks. Relapsing Fever can be divided into Louse-borne relapsing fever (LBRF), soft tick-borne relapsing fever and hard tick-borne relapsing fever.

Louse-borne relapsing fever is caused by a single Borrelia pathogen, B. recurrentis. The first case linked with spirochetal etiology and body louse transmission occurred in late 19th –early 20th century.

Soft tick-borne relapsing fever was first discovered to cause disease in humans in the early 20th century. The disease is caused by B. crocidurae, B. duttoni, B. persica, B. latyshervi, and B. hisponica, B. venezuelensis, B. mazotti, B. hermsii, B. turicatae, and B. parkeri.

Hard-tick relapsing fever infections are currently known to be caused by B. miyamotoi. B. miyamotoi was discovered in 2005 in Japan. In 2011, the first human case of B. miyamotoi infection was reported in Russia. In the US, the first case was reported in 2013.

B. coriaceae

B. coriaceae

B. hermsii

B. hermsii

How Are Relapsing Fever Borrelia Transmitted?

The Relapsing Fever Borrelia is transmitted to humans by body louse, soft ticks, and hard ticks.


B. recurrentis is the only relapsing fever Borrelia transmitted by body lice from person to person; humans are the reservoir host.

Borrelia causing soft tick-borne relapsing fever are transmitted by soft-bodied ticks of the genus Ornithodoros. Reservoir hosts in US are: mice, chipmunks, squirrels, prairie dogs, and burrowing owls. Most relapsing fever Borrelia species are vector and reservoir host specific.

People become exposed when they sleep in cabins and other rustic buildings in which rodents have built nests. These nests are usually located inside the walls or in the attic or crawl space. The ticks emerge at night and feed briefly, like bed bugs. Because the bites are quick and painless, most people do not know that they have been bitten.

Borrelia causing hard-tick relapsing fever (B. miyamotoi) infections are transmitted by two species of deer ticks. The Eastern black-legged tick, Ixodes scapularis, and the Western black-legged tick, I. pacificus, are known vectors for B. miyamotoi, the causative agent of Relapsing Fever in the US. In Eastern Europe and Russia, the vector is I. ricinus and in Japan I. persulcatus.

These ticks are already known to transmit several diseases, including Lyme disease, Anaplasmosis, and Babesiosis.

What Are the Infected Regions?

Relapsing Fever occurs all over the world. B. recurrentis is only endemic in the horn of Africa and has occurred in Asia and Europe. It has been associated with war, famine and refugees, wherever there is crowding, limited changes of clothing, limited washing facilities, and absence of “delousing” treatments.

Borrelia causing soft tick-borne relapsing fever, B. crocidurae and B. duttoni are found in Africa; B. persica, B. latyshervi, and B. hisponica are found in Asia and Middle East. B. venezuelensis, B. mazotti are common in Central and South America. In North America, B. hermsii is present in forested mountains at 1,000 – 2,700 meters; rustic cabins; B. turicatae in desert, semi-desert, scrub landscapes, caves, rodent burrows and B. parkeri has been recently found in ticks in Florida.

Borrelia causing hard-tick relapsing fever, B. miyamotoi, is currently found in the United States, Central Europe, Russia, and Japan.

What Are the Symptoms?

Clinical manifestations are severe for most tick-borne relapsing fever; headache, neck stiffness, arthralgia, myalgia, ecchymosis, epistaxis, and petechiae.

Complications include ARDS, decreased sensorium, myocarditis, hepatitis, abortion or stillborn and death. However based on recent studies, most patients have symptoms similar to Lyme disease and do not even remember having relapsing fevers. Infection by this bacteria tends to produce symptoms similar to Lyme disease, including fever, headache, fatigue, chills, myalgia, joint and muscle pain, loss of appetite, nausea, disorientation or memory loss, lack of coordination, as well as more severe conditions of neurological disease.

How Is Relapsing Fever Diagnosed?

Since the symptoms and signs of relapsing fever are relatively nonspecific, laboratory testing can help the physician in making the correct diagnosis. The diagnosis of Relapsing Fever should be considered in patients who live in or travel to areas that are endemic for Relapsing Fever and/or experience Relapsing Fever or have Lyme-like symptoms but are negative by all Lyme disease tests.

Click here on how to order a test kit from IGeneX. Test kits can be ordered by both patients and physicians.

FOR HEALTHCARE PROFESSIONAL: Click here for more information on the type of diagnostic tests to detect TBRF Borrelia.

Can A Tick Be Tested?

At IGeneX, ticks can be tested for presence of TBRF Borrelia by a PCR test. Any tick including one that has been removed from a patient or found in the yard, can be sent to IGeneX for testing.

Click here for more information on how to test a tick.