Can Baby Ticks Spread Borrelia miyamotoi? What We Know
Baby ticks may carry Borrelia miyamotoi
Infected female ticks can pass the bacterium to their offspring
Larval ticks may therefore hatch already infected
Borrelia miyamotoi is an emerging tick-borne bacterium that can be transmitted by blacklegged ticks. Unlike the bacteria that cause Lyme disease, B. miyamotoi may be passed from an infected female tick directly to her eggs. This means that larval ticks—sometimes called baby ticks—may already be infected before taking their first blood meal.
In their article, Borrelia miyamotoi: A Comprehensive Review, Cleveland and colleagues discuss B. miyamotoi as an emerging tick-borne pathogen and explain how it may be transmitted from an infected female tick to her offspring.¹
How Can Baby Ticks Carry Borrelia miyamotoi?
The transmission of a pathogen from an infected female tick to her eggs is called transovarial transmission, or vertical transmission.
Cleveland and colleagues reviewed the proposed vertical transmission of B. miyamotoi:¹
- An adult female tick infected with B. miyamotoi lays eggs.
- Larvae hatch from the eggs already infected with B. miyamotoi.
- The larvae may remain infected as they develop into nymphs and adult ticks.
This is important because larval ticks are extremely small and may be difficult to see. A person may not realize that a larval tick has attached and begun feeding.
Can Larval Ticks Transmit Disease?
Yes. Larval ticks may be capable of transmitting B. miyamotoi if they acquired the bacterium from the infected female tick that laid the eggs.
This differs from the usual transmission cycle of the bacteria that cause Lyme disease. Larval ticks generally acquire Borrelia burgdorferi after feeding on an infected animal. However, larvae may hatch already infected with B. miyamotoi.
Therefore, a larval tick should not automatically be considered harmless simply because it has not previously taken a blood meal.
How Else Do Ticks Acquire Borrelia miyamotoi?
Ticks may also acquire B. miyamotoi while feeding on an infected animal. This is called horizontal transmission.
Cleveland and colleagues reviewed the proposed horizontal transmission of B. miyamotoi:¹
- Larval, nymphal, or adult ticks feed on an infected animal host.
- The ticks acquire B. miyamotoi during the blood meal.
- The ticks may remain infected as they progress through later life stages.
How Quickly Can Borrelia miyamotoi Be Transmitted?
Transmission may occur relatively early after a tick attaches.
“B. miyamotoi can be transmitted from infected ticks to naïve mice during the first 24 hours of feeding,” Cleveland and colleagues wrote.¹
The researchers reported that B. miyamotoi may initially be transmitted through bacteria already present in the tick’s salivary glands. Additional bacteria may later move from the tick’s midgut to the salivary glands during feeding.
Animal studies do not establish an exact transmission time for every human tick bite. However, these findings suggest that the risk of B. miyamotoi transmission may begin earlier than many people expect.
Because transmission may occur early, prompt tick removal remains important whenever a tick is discovered.
Is Borrelia miyamotoi the Same as Lyme Disease?
No. Borrelia miyamotoi is related to the bacteria that cause Lyme disease, but it causes a different tick-borne illness.
B. miyamotoi is classified as a relapsing fever Borrelia. The illness is often called hard tick relapsing fever because it is transmitted by hard-bodied ticks, including the same blacklegged ticks that transmit Lyme disease.
Patients with B. miyamotoi infection typically do not develop the expanding erythema migrans rash commonly associated with early Lyme disease. However, the absence of a rash does not exclude either infection.
What Are the Symptoms of Borrelia miyamotoi Infection?
Shapiro and Wormser summarized several clinical concerns associated with B. miyamotoi infection in the Journal of the American Medical Association.²
Reported symptoms may include:
- Fatigue or malaise
- Headache
- Muscle pain
- Joint pain
- Chills
- Fever
- Nausea
- Dizziness
Although B. miyamotoi is associated with relapsing fever, fever may be absent, infrequent, or may not follow a clearly relapsing pattern. The presentation can vary from one patient to another.
Patients in the United States typically do not have an erythema migrans rash. Severely immunocompromised patients may develop neurologic complications, including chronic meningitis.
What Laboratory Abnormalities Can Occur?
Some patients with B. miyamotoi infection develop:
- Leukopenia, or a low white blood cell count
- Thrombocytopenia, or a low platelet count
- Elevated liver enzymes
These findings are not unique to B. miyamotoi. Leukopenia, thrombocytopenia, and elevated liver enzymes may also occur with anaplasmosis and ehrlichiosis. Clinical symptoms, exposure history, and appropriate testing must therefore be considered together.
How Is Borrelia miyamotoi Diagnosed?
Diagnosing B. miyamotoi infection can be challenging. Routine Lyme disease antibody tests are not designed to reliably diagnose B. miyamotoi.
Testing may include polymerase chain reaction, or PCR, during the acute stage of illness. Antibody testing directed against the GlpQ protein may also be used in some settings.
However, test availability is limited, and a negative result may not always exclude infection. The timing of the test and the patient’s clinical presentation are important.
How Is Borrelia miyamotoi Treated?
Most reported cases have responded to antibiotics that are also used to treat other tick-borne bacterial infections.
Doxycycline is commonly used. Amoxicillin and ceftriaxone have also been used in reported cases, depending on the patient’s age, clinical presentation, medication tolerance, and whether neurologic involvement is suspected.
Most uncomplicated infections improve with appropriate antibiotics. More research is needed to determine the most effective treatment regimens and the long-term outcomes of patients with persistent or recurrent symptoms.
Can Baby Ticks Spread Lyme Disease?
Larval ticks are generally not born infected with Borrelia burgdorferi, the primary bacterium responsible for Lyme disease in North America. Instead, they typically acquire the bacteria after feeding on an infected animal.
In contrast, B. miyamotoi can be passed from an infected female tick to her eggs. This means that a newly hatched larval tick may carry B. miyamotoi before feeding on its first animal or human host.
Although larval ticks rarely transmit Lyme disease because they usually hatch uninfected with Borrelia burgdorferi, they may still transmit Borrelia miyamotoi if they inherited the bacterium from an infected female tick.
Is Borrelia miyamotoi Contagious?
Borrelia miyamotoi is not considered contagious through ordinary person-to-person contact. People generally become infected through the bite of an infected tick.
A person would not be expected to spread the infection through touching, coughing, sharing food, or routine household contact.
Frequently Asked Questions
Can a baby tick bite a person?
Yes. Larval ticks can attach to and feed on people. Because they are extremely small, their bites may go unnoticed.
Can a larval tick transmit Borrelia miyamotoi?
Yes. A larval tick may hatch already infected if an infected female tick passed Borrelia miyamotoi to her eggs.
How do people get Borrelia miyamotoi?
People acquire Borrelia miyamotoi through the bite of an infected tick, including a larval, nymphal, or adult blacklegged tick.
Can you get Borrelia miyamotoi without a rash?
Yes. Most patients with Borrelia miyamotoi infection do not develop the characteristic erythema migrans rash associated with Lyme disease.
Does everyone with Borrelia miyamotoi develop relapsing fever?
No. Although the illness is classified as a hard tick relapsing fever, some patients do not report fever, and others do not experience a clearly relapsing fever pattern.
Can Borrelia miyamotoi spread from person to person?
Current evidence indicates that infection occurs through the bite of an infected tick rather than through routine person-to-person contact.
Clinical Takeaway
The ability of an infected female tick to pass Borrelia miyamotoi to her offspring distinguishes this bacterium from the usual transmission pattern of the bacteria that cause Lyme disease.
Larval ticks are extremely small, may be difficult to detect, and may already carry Borrelia miyamotoi before taking their first blood meal.
A baby tick should not automatically be considered harmless, particularly when evaluating possible exposure to Borrelia miyamotoi.
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References
- Cleveland DW, Anderson CC, Brissette CA. Borrelia miyamotoi: A Comprehensive Review. Pathogens. 2023;12(2):267. doi:10.3390/pathogens12020267.
- Shapiro ED, Wormser GP. Lyme Disease in 2018: What Is New (and What Is Not). JAMA. 2018;320(7):635-636. doi:10.1001/jama.2018.10974.
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
