Borrelia miyamotoi: Symptoms, Testing, and Treatment

Emerging tick-borne relapsing fever infection
Often mistaken for Lyme disease and other tick-borne illnesses
Early recognition may improve diagnosis and treatment

Borrelia miyamotoi (B. miyamotoi) is an emerging tick-borne bacterium carried by the same blacklegged (deer) tick that transmits Borrelia burgdorferi, the cause of Lyme disease. Although first recognized as a cause of human illness in the United States in 2013, awareness of B. miyamotoi infection has continued to grow as testing improves. In their article, Della-Giustina and colleagues² review what clinicians should know about this increasingly recognized infection.

Borrelia miyamotoi is a relapsing fever bacterium transmitted by blacklegged (deer) ticks. Although it is carried by the same tick that spreads Lyme disease, it belongs to a different group of Borrelia bacteria and typically presents with fever, headache, fatigue, and muscle aches rather than the classic Lyme disease rash.

How is B. miyamotoi different from Lyme disease?

Although both infections are transmitted by blacklegged (deer) ticks, B. miyamotoi belongs to the relapsing fever group of Borrelia, whereas Lyme disease is caused by B. burgdorferi. Fever is more common with B. miyamotoi, while an erythema migrans rash is uncommon. In addition, B. miyamotoi may be transmitted by larval ticks through transovarial transmission and appears to be transmitted more rapidly than Lyme disease in experimental studies.

Where is B. miyamotoi found?

Borrelia miyamotoi has been detected in several tick species, including the blacklegged (deer) tick (Ixodes scapularis). Infected ticks have been identified throughout the northeastern and upper Midwestern United States, California, Europe, and Asia.

What stage of deer ticks transmits B. miyamotoi?

Unlike B. burgdorferi, B. miyamotoi can be transmitted by larval, nymphal, and adult ticks. Because infected female ticks may pass the organism directly to their offspring through transovarial transmission, even larval ticks may carry and transmit the infection.

How fast can B. miyamotoi be transmitted?

Experimental studies suggest transmission can occur relatively quickly. According to Della-Giustina and colleagues, “B. miyamotoi can be transmitted 10% of the time within the first 24 hours of attachment, increasing steadily to reach 73% for a complete feeding. Thus, transmission of B. miyamotoi is more rapid than transmission of B. burgdorferi.”²

Although these findings raise important clinical questions, the exact timing of transmission in humans remains uncertain.

What are the symptoms of B. miyamotoi infection?

The most commonly reported symptoms include:

• Fever, which may be relapsing
• Headache
• Fatigue or malaise
• Muscle aches (myalgias)
• Chills
• Occasional nausea

Some patients also develop laboratory abnormalities such as leukopenia and elevated liver enzymes, findings that can resemble anaplasmosis. Unlike Lyme disease, an erythema migrans rash appears to be uncommon, occurring in approximately 11% of patients in one reported case series.

How is B. miyamotoi diagnosed?

Diagnosing B. miyamotoi infection can be challenging because commercially available testing remains limited.

As Della-Giustina and colleagues note, “No test specific to B. miyamotoi has been approved by the United States Food and Drug Administration as of October 2020.”

The most specific laboratory method available at several public health and commercial laboratories is polymerase chain reaction (PCR) testing of blood or cerebrospinal fluid targeting the B. miyamotoi GlpQ gene or related genetic targets. PCR is generally most useful early in illness before antibodies have developed.

Learn more about testing for Borrelia miyamotoi, including the potential role of the C6 peptide assay.

Serologic testing for B. miyamotoi IgM and IgG antibodies is available through some commercial laboratories. Interpretation may be challenging because antibody responses may cross-react with other spirochetes, and testing is less informative early in infection.

Investigational approaches such as the TBD Serochip, an array-based assay capable of detecting multiple tick-borne infections simultaneously, remain promising but are not yet widely available.

Treatment of B. miyamotoi

There are no randomized clinical trials establishing the optimal treatment for B. miyamotoi infection. Most treatment recommendations are based on laboratory susceptibility studies, clinical experience, and reported case series.

Antibiotics that have been used include doxycycline, ceftriaxone, and azithromycin. According to Della-Giustina and colleagues, “In vitro analysis has shown the susceptibility of B. miyamotoi to ceftriaxone, azithromycin, and doxycycline, with resistance to amoxicillin.” Additional clinical studies are needed to determine the most effective treatment regimen.

Should antibiotics be given after a tick bite?

Experimental studies suggest that B. miyamotoi may be transmitted more rapidly than B. burgdorferi. This observation has raised questions about whether current Lyme disease prophylaxis recommendations adequately address B. miyamotoi.

As the authors note, “Understanding this more rapid transmission of infection of B. miyamotoi may be a consideration in determining prophylactic treatment for tick bites with a shorter time of attachment in endemic areas for B. miyamotoi.”

However, there are currently no evidence-based clinical trials supporting prophylactic antibiotic treatment specifically for B. miyamotoi following a tick bite. Clinicians should consider the patient’s exposure history, symptoms, local epidemiology, and current treatment guidelines when making management decisions.

Frequently Asked Questions

What is Borrelia miyamotoi?

Borrelia miyamotoi is a relapsing fever bacterium transmitted by blacklegged (deer) ticks. Although carried by the same ticks that transmit Lyme disease, it causes a different tick-borne illness.

How is Borrelia miyamotoi different from Lyme disease?

Although both infections are spread by blacklegged ticks, B. miyamotoi belongs to the relapsing fever group of Borrelia, whereas Lyme disease is caused by B. burgdorferi. Fever is more common, while an erythema migrans rash is much less common with B. miyamotoi.

How is Borrelia miyamotoi diagnosed?

PCR testing of blood is generally the most useful laboratory test early in illness. Antibody testing is available through some commercial laboratories but may be difficult to interpret because of cross-reactivity and delayed antibody development.

Can Borrelia miyamotoi cause a Lyme disease rash?

Usually not. Unlike Lyme disease, an erythema migrans rash has been reported in only a small percentage of patients with B. miyamotoi infection.

Clinical Takeaway

Borrelia miyamotoi is an increasingly recognized tick-borne infection that shares the same vector as Lyme disease but differs in its biology, clinical presentation, and transmission.

Because awareness remains limited and symptoms overlap with Lyme disease and other tick-borne infections, clinicians should consider B. miyamotoi in patients with compatible illness following blacklegged (deer) tick exposure, particularly when fever, leukopenia, or elevated liver enzymes are present.

Greater awareness of B. miyamotoi may lead to earlier diagnosis and more timely treatment of this emerging tick-borne disease.

Related Articles

• Could Borrelia miyamotoi infections explain persistent symptoms in Lyme disease patients?
• The best antibiotics to treat Borrelia miyamotoi
• Tick-borne relapsing fever: Symptoms, diagnosis, and treatment

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Dr. Daniel Cameron, MD, MPH
Lyme disease clinician with over 30 years of experience and past president of ILADS.

Symptoms • Testing • Coinfections • Recovery • Pediatric • Prevention