Borrelia turcica IgG

Borrelia turcica is a recently identified tick-borne pathogen that, although not yet fully understood in terms of its clinical implications, raises concerns for potential human illness. 

With growing evidence of its presence in southeastern Europe, particularly in Greece and Turkey, clinicians should consider B. turcica in the differential diagnosis of unexplained febrile illnesses, especially in individuals with a history of exposure to Hyalomma aegyptium ticks or reptiles.

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, 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 turcica?

Borrelia turcica is a tick-borne bacterium found primarily in the southeastern European regions, including Greece and Turkey, and is vectored by Hyalomma aegyptium ticks. The species is associated with tortoises of the Testudo genus, which serve as the primary reservoir hosts. 

Borrelia turcica is a newly identified species that, along with other unknown Borrelia strains, forms a third group separate from the Lyme disease and relapsing fever groups. Genetic analysis of multiple genes confirmed that B. turcica is genetically distinct from the other two groups.

While the pathogenicity and zoonotic potential of B. turcica in humans are not fully understood, its genetic similarity to other Borrelia species raises concerns about potential clinical manifestations, including fever and spirochetemia, similar to relapsing fever. 

The presence of B. turcica antibodies in humans may indicate exposure to this pathogen, although no direct symptoms or human illness have been conclusively linked to it. Further studies are needed to determine its full clinical significance and potential for causing disease in humans. 

Because its pathogenicity is relatively unknown, clinicians may consider B. turcica in cases of unexplained febrile illness, especially in individuals with known exposure to tick bites or reptiles.

What is Borrelia turcica IgG?

Borrelia turcica IgG is a type of antibody produced by the immune system against this spirochete. These antibodies remain detectable long after the infection resolves, serving as markers of past or present infection.

While IgG antibodies to B. turcica can be present in both active and past infections, their presence alone does not confirm active disease. 

Who Should Be Tested for Borrelia turcica IgG?

Individuals who may benefit from B. turcica IgG testing include those with unexplained febrile illness or other symptoms resembling tick-borne diseases, particularly those who have been exposed to Hyalomma aegyptium ticks through contact with tortoises or small mammals. 

This test could also be valuable for individuals involved in the international reptile trade or those who have recently traveled to areas where these ticks are endemic. 

As B. turcica is closely related to other Borrelia species, the test may help clinicians rule out or confirm exposure to this emerging pathogen, especially in patients with a history of tick bites or interactions with reptiles. 

Further research is needed to better understand its clinical significance and establish clear diagnostic guidelines.

Test Procedure and Interpretation

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

Test Procedure and Preparation Requirements

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

Normal Reference Ranges

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

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

Clinical Implications of Elevated Levels

Elevated Borrelia turcica IgG levels typically indicate that the patient has been exposed to B. turcica in the past or is currently experiencing an active infection. However, since IgG antibodies can persist after an infection has cleared, high levels do not necessarily confirm active disease. 

Elevated IgG levels should be interpreted alongside the patient’s clinical history and symptoms, and further diagnostic tests, such as IgM testing or PCR, should confirm the diagnosis.

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