What You Need to Know About Borrelia Miyamotoi

Researchers are paying more and more attention to Borrelia miyamotoi, a spiral-shaped bacteria related to the types of Borrelia that cause Lyme disease. This bacteria is prevalent on both coasts of the US and is a known cause of Tick-Borne Relapsing Fever, or TBRF.

What is Borrelia miyamotoi?

Borrelia miyamotoi is one of the most recently discovered species of Relapsing Fever-causing bacteria.  In fact, some experts consider it the causative agent of an “emerging” tick-borne disease, and it is not even reportable to the CDC yet.

As will be addressed in detail later in this blog, what makes B. miyamotoi different from other TBRF bacteria is that it is spread by a different type of tick. Whereas most TBRF cases in the US are spread by soft ticks, B. miyamotoi is spread by hard ticks – including the same species of ticks that spread Lyme disease.

Keep reading to learn more about B. miyamotoi and what it means for patients, doctors, and testing and diagnostics.

What you need to know about Borrelia miyamotoi

1. B. miyamotoi is closely related to other TBRF-causing bacteria.

B. miyamotoi is one of several closely related bacteria that cause Tick-Borne Relapsing Fever in the US. Like the bacteria that cause Lyme, these are spiral-shaped bacteria or “spirochetes” that cause serious symptoms, including rashes and fevers.

TBRF gets its name from the “relapsing” fevers that show up in some patients. According to the CDC, these are typically high fevers (e.g., 103 degrees) that last for about 3 days, followed by about 7 days without fever, then 3 days of fever again, and so on. Symptoms typically show up within 7 days of infection and can repeat several times if not treated with antibiotics.

However, it is important to note that not all patients experience fevers. Like Lyme disease, TBRF symptoms can vary widely among patients. The non-specific nature of these symptoms can lead to misdiagnosis, especially in the case of patients who think they have Lyme but test negative because the test is not designed to detect other types of bacteria, like those that cause TBRF.

2. B. miyamotoi was first discovered in Japan in 1995.

In 1995, Masahito Fukunaga et al. discovered and named Borrelia miyamotoi after the researcher who had first isolated spirochetes from hard-bodied ticks in Japan. According to the CDC, it wasn’t until 2011 that the first human case of B. miyamotoi infection was found in Russia. The first North American human case was found in 2013, though some research shows the presence of the bacteria in ticks in Connecticut as far back as 2001.

3. Some experts consider Borrelia miyamotoi disease separate from TBRF.

The CDC and some other entities refer to the illness caused by B. miyamotoi as Borrelia miyamotoi disease. Though the CDC does not provide explicit reasoning for this, there are some similarities and differences between B. miyamotoi and other TBRF-causing bacteria that may be of interest to readers. One difference, which will be covered more in detail later, is that B. miyamotoi is spread by a different type of tick than other TBRF-causing bacteria in North America.

However, what CDC calls Borrelia miyamotoi disease causes very similar symptoms to those of TBRF, namely fever, chills, and headache. Additionally, infections caused by B. miyamotoi and other TBRF-causing bacteria can be detected with both PCR tests and serological tests, and both are treated by antibiotics, usually doxycycline (as with TBRF and Lyme) but sometimes amoxicillin or ceftriaxone. For children and pregnant women, erythromycin or penicillin can be successful.

4. Even baby ticks can be infected with B. miyamotoi.

As IGeneX has covered in numerous articles before, humans are most commonly infected by bites from ticks in the nymph stage of development. This is because ticks at this stage have previously fed on animal reservoirs in the larval stage – such as the white-footed mouse – and then move onto blood meals from larger animals, such as dogs or humans, where they are able to transmit pathogens without being noticed due to their small size.

However, research has shown that B. miyamotoi can actually be spread directly from adult female ticks to their offspring through something called transovarial transmission. In other words, baby ticks can be “born” already infected with B. miyamotoi, rather than having to feed on an infected host (as is the case with Lyme-causing bacteria). Larval ticks still make up a very small percentage of overall infected ticks, with a recent San Francisco State University study showing just 0.11% of larvae in the sample being infected with B. miyamotoi. However, the prevalence of infection increases at each stage of life, and transovarial transmission gives B. miyamotoi a head start.

5. B. miyamotoi is the only known TBRF bacteria spread by hard ticks.

One of the main differences between Lyme disease and TBRF is that most cases of TBRF in the US result from the bites of soft ticks. Soft ticks come from the Argasidae family, as opposed to the Ixodidae family of hard-bodied ticks. Soft ticks have more rounded bodies and are missing the hard shell around the mouthparts that is characteristic of hard-bodied ticks. What’s more, soft ticks can transmit disease – typically via the bacteria B. hermsii, the most common TBRF pathogen in the U.S. – in under 15 minutes.

However, B. miyamotoi is the only cause of TBRF that is known to be spread by hard ticks from the Ixodidae family. In the US, B. miyamotoi is found specifically in Eastern and Western blacklegged ticks (also known as deer ticks) – the main causes of Lyme disease in the US. This means that those living in blacklegged tick-endemic regions, including states along both coasts, are at risk of both Lyme disease and TBRF. It is also possible to be infected with both Lyme and TBRF from the same tick bite.

Doctor uses an in-ear thermometer to take the temperature of a patient.
6. Symptoms of a B. miyamotoi infection look a lot like Lyme symptoms.

It’s important to understand that symptoms of B. miyamotoi infections and TBRF, in general, can look just like Lyme symptoms. These include:

  • Fever – can be recurring in a pattern of 3 days with fever, 7 days without, and so on
  • Chills
  • Headaches
  • Muscle and joint pain

Again, not all patients experience fevers, and patients who do have fevers will not necessarily experience recurring fevers. And since the same hard-bodied ticks that carry Lyme disease can also carry B. miyamotoi, you can be infected with both diseases at once (among other tick-borne co-infections). This means it is extremely important for doctors to test patients for all possible disease-causing bacteria, including B. miyamotoi.

IGeneX offers comprehensive tick-borne disease testing designed to detect all major tick-borne disease pathogens in the US, not just those that cause Lyme. Learn more about testing for TBRF with IGeneX today.



Great information on a pathogen that isn’t reportable yet. This is a real problem. Prevalence is completely unknown due to this – which desperately needs to change. Borrelia Miyamotoi (Bm) could very well be a reason many are going undiagnosed. Since Lyme testing will not pick it up, many with legitimate symptoms are being sent home after testing negative for Lyme.

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