Borrelia turicatae

Borrelia turicatae is a bacterium that causes tick-borne relapsing fever (TBRF), a multi-system illness marked by recurring episodes of fever. 

While this species of Borrelia is primarily found in the Americas, clinicians should understand its transmission, clinical manifestations, diagnostic approaches, and management to ensure accurate diagnosis and prompt treatment.

What is Borrelia?

Borrelia spp. are spirochetes responsible for Lyme disease (LD) and relapsing fever (RF), transmitted by ticks and lice. 

LD, caused by Borreliella spp. (formerly Borrelia), is the most common vector-borne disease in temperate regions. It is primarily caused by B. burgdorferi and B. mayonii, but it is also caused by B. afzelii and B. garinii.

Symptoms include erythema migrans, fatigue, fever, and musculoskeletal pain. Untreated infections can lead to neuroborreliosis, arthritis, and Lyme carditis. 

RF, caused by species like B. miyamotoi, B. hermsii, B. turicatae, and Candidatus B. johnsonii, presents with recurring fever, headache, and myalgia, and can cause severe complications, including meningitis.

Borrelia spp. are commonly found in ticks that infest rodents, birds, and wild ungulates. The distribution of these ticks, particularly in the Mediterranean and the U.S., has expanded, increasing the prevalence of Borrelia infections. 

A recent study identified five Borrelia species in U.S. patients, including B. burgdorferi and B. mayonii (LD), and B. miyamotoi, B. hermsii, and Candidatus B. johnsonii (RF). The discovery of Candidatus B. johnsonii, previously linked only to bat ticks, suggests it may also cause human illness.

Clinicians should be aware of the distinct clinical features of LD and RF for timely diagnosis and treatment. Preventative measures like tick repellents are foundational in reducing transmission. 

What is Borrelia turicatae?

Borrelia turicatae is a spirochete responsible for tick-borne relapsing fever (TBRF), primarily transmitted by the Ornithodoros turicata tick, which thrives in caves and rodent burrows. It seems to be most prevalent in Texas and Latin America. 

In the U.S., Borrelia turicatae and Borrelia hermsii are the two strains most associated with TBRF.

Historically, B. turicatae was considered a pathogen of rural areas, but recent studies indicate that it has established endemic foci in densely populated urban regions, particularly in Texas. The increasing prevalence of homelessness and human activity in urban parks has further raised concerns about the spread of this pathogen.

The infection is challenging to diagnose due to its nonspecific symptoms, which often mimic other febrile illnesses. Symptoms commonly include recurring episodes of fever, chills, headache, and muscle pain, but these can be mistaken for other conditions. 

The bites of Ornithodoros turicata ticks are often painless and go unnoticed, making it difficult to diagnose TBRF early. 

Genetic analysis of B. turicatae has shown significant diversity, with four main genotypes identified. This diversity points to the complexity of the pathogen's spread and persistence in nature. Additionally, B. turicatae has been found in a variety of hosts, including wild canines, which may play a role in the pathogen's dispersal.

Who Should Get Tested for Borrelia turicatae Infection?

Testing for B. turicatae infection should be considered for individuals:

• Exhibiting recurring fevers, chills, and joint pain, particularly when these symptoms are cyclical.
• With a history of exposure to Ornithodoros ticks, such as living in or traveling to endemic areas.
• Presenting with unexplained recurrent fevers after excluding other common causes, like malaria or other bacterial infections.

Test Procedure and Interpretation

The following section outlines testing procedures and results interpretation for Borrelia turicatae:

Test Procedure and Preparation Requirements

Borrelia turicatae testing requires a blood sample, typically collected via venipuncture. The patient generally does not have specific preparation requirements, although it’s always important to confirm this with the ordering provider.

Normal Reference Ranges

Normal reference ranges for Borrelia turicatae may vary slightly depending on the laboratory performing the test. However, a negative result generally indicates no detectable immune response to B. turicatae at the time of testing. 

Positive results, especially in the context of clinical symptoms, suggest past or ongoing infection.

What Do Positive Borrelia turicatae Test Results Mean?

Positive test results include:

Microscopy

A positive blood smear is suggestive of TBRF but not specific to B. turicatae.

PCR 

A positive PCR result confirms the presence of B. turicatae DNA, making it the most accurate test.

Serology

A positive result suggests exposure to B. turicatae, though species-specific tests are limited, and cross-reactivity is common.

BipA (Borrelia immunogenic protein A) is a protein found in Borrelia species, including Borrelia turicatae, which causes tick-borne relapsing fever (TBRF). It is considered a species-specific antigen, meaning it is unique to certain Borrelia species.

Serologic BipA testing for Borrelia turicatae could serve as a diagnostic tool for identifying tick-borne relapsing fever (TBRF) by detecting species-specific antibodies, improving the detection of endemic regions and aiding in accurate diagnosis, especially given the nonspecific symptoms and unnoticed tick bites.

What Do Negative Borrelia turicatae Test Results Mean?

Negative test results may have the following clinical significance:

Microscopy 

Negative results do not rule out infection, as spirochetes may not always be present in peripheral blood.

PCR 

A negative PCR result may indicate no infection, but false negatives can occur, especially if the sample was taken during an afebrile period.

Serology

Negative results can occur early in the infection or in immunosuppressed individuals. The timing of the test and clinical symptoms should be considered.

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