Borrelia andersonii - IgG

What Does a Positive or Elevated IgG Result Mean?

A positive or elevated IgG result for Borrelia andersonii suggests:

• Past exposure to this species of Borrelia

• Your immune system has developed long-term antibodies, which may persist even after the infection has resolved

• It does not confirm an active infection or disease, especially in the absence of symptoms

Because B. andersonii is not a well-established human pathogen, this result should be interpreted cautiously and in the context of other findings.

Clinical Relevance

• Borrelia andersonii is not currently recognized as a confirmed cause of human illness, but its detection may indicate environmental exposure to Borrelia species or cross-reactivity with more pathogenic strains such as Borrelia burgdorferi (Lyme disease).

• In patients with symptoms of tickborne disease—such as fatigue, fever, joint pain, or neurological issues—this result may be considered alongside other Borrelia-specific IgG/IgM results, PCR testing, and clinical history.

Next Steps

• Speak with your healthcare provider to interpret this result in the context of your symptoms, history of tick exposure, and other test results.

• If additional Borrelia markers (like B. burgdorferi) are positive and symptoms are present, further evaluation for Lyme or related tickborne diseases may be warranted.

• In most cases, no treatment is needed for a positive B. andersonii IgG alone unless other evidence of active disease is found.

Summary

The Borrelia andersonii – IgG test detects long-term antibodies that suggest past exposure to this lesser-known Borrelia species. A medium or elevated result is not diagnostic of Lyme disease or any specific illness, but may reflect cross-reactivity or environmental exposure. Interpretation should be made by your healthcare provider in the context of your full clinical picture.

What is Borrelia andersonii – IgG?

Borrelia andersonii is a species of Borrelia, a genus of spiral-shaped bacteria that includes several species known to cause tickborne illnesses such as Lyme disease and relapsing fever. While Borrelia andersonii has not been definitively linked to human disease, it has been isolated from Ixodes ticks (the same ticks that transmit Lyme disease) and from wild animals in parts of North America, suggesting it may play a role in the broader ecology of tickborne infections.

The IgG antibody test for Borrelia andersonii measures the body’s long-term immune response to this bacterium. IgG antibodies typically appear weeks after exposure and can remain in the bloodstream for months or even years, indicating past exposure or infection.

What Does a Medium Result Mean?

A medium IgG result indicates a moderate level of antibodies, which may reflect:

• A recent or past exposure to Borrelia andersonii

• A low-level or cross-reactive immune response, possibly due to exposure to a related Borrelia species

• A borderline finding, which may or may not be clinically significant

Follow-up testing and clinical evaluation can help determine whether additional investigation or treatment is necessary.