Borrelia andersonii - IgM

What Does a Positive or Elevated IgM Result Mean?

A positive or elevated IgM result for Borrelia andersonii suggests:

• Recent or ongoing immune response to B. andersonii or a related species

• Possible cross-reactivity with other Borrelia bacteria, such as Borrelia burgdorferi (the cause of Lyme disease)

• A nonspecific immune reaction, especially if no other Borrelia markers are elevated

Since B. andersonii is not known to cause disease in humans, a positive IgM result does not confirm active infection or illness on its own.

Clinical Considerations

• A positive or medium IgM for B. andersonii is not sufficient to diagnose Lyme disease or any specific tickborne illness.

• This marker may appear in individuals with environmental exposure to ticks or who have been infected with other Borrelia species.

• If symptoms such as fever, fatigue, joint pain, or neurological issues are present, further testing (including Borrelia burgdorferi IgM/IgG, PCR, or Western blot) is usually recommended.

Next Steps

• Discuss your results with your healthcare provider, especially if you have symptoms of a tickborne illness or known tick exposure.

• Additional testing may be needed to rule in or rule out Lyme disease or other infections.

• If no other markers are positive and you feel well, no treatment is typically required for an isolated B. andersonii IgM result.

Summary

The Borrelia andersonii – IgM test detects early immune response to a lesser-known Borrelia species. A medium or elevated result may suggest recent exposure or cross-reactivity, but it is not diagnostic of an active infection. Interpretation should be based on your symptoms, exposure history, and results from other tickborne disease markers. Always consult your healthcare provider for a comprehensive evaluation.

What is Borrelia andersonii – IgM?

Borrelia andersonii is a species within the Borrelia genus, a group of spiral-shaped bacteria that includes known causes of Lyme disease and relapsing fever. Borrelia andersonii has been found in Ixodes ticks and certain wild animals in North America, but it is not currently recognized as a confirmed human pathogen. However, its presence on testing panels may indicate exposure to Borrelia bacteria or potential cross-reactivity with related species.

The IgM antibody test for Borrelia andersonii detects early immune response—specifically IgM antibodies, which typically appear within 1–2 weeks of infection or exposure. This makes IgM testing useful for identifying recent or possible current exposure to Borrelia species.

What Does a Medium Result Mean?

A medium IgM result indicates a moderate level of early antibodies, which could reflect:

• An early or low-level immune response to a Borrelia species

• A resolving immune reaction, if exposure occurred recently

• A borderline or nonspecific result, which should be interpreted with caution

In the absence of symptoms or supporting test results, a medium IgM result is typically not diagnostic and may not require treatment.