Archive for the ‘Borrelia Miyamotoi (Relapsing Fever Group)’ Category

California’s First CDC-Confirmed Case of Borrelia Miyamotoi

California’s first CDC-confirmed case of Borrelia miyamotoi

By Lonnie Marcum

May 4, 2023

A recent case reminds us that Lyme disease isn’t the only tick-borne disease we need to worry about.

Last year, the CDC confirmed California’s first known case of Borrelia miyamotoi—a tick-borne pathogen that causes a relapsing-fever illness in humans.

This discovery highlights the need for increased awareness and surveillance of emerging tick-borne illnesses across the United States.

In this case, a man from Marin County, California, sought care at a neurology clinic in San Francisco. His symptoms included recurring fever, night sweats, mild vision changes and nausea. The fevers typically lasted one day and would recur every 10-14 days. At the time, he was also undergoing monoclonal antibody therapy for multiple sclerosis.

His standard blood work was negative for fungi, Lyme disease, brucellosis and leptospirosis. Chest x-rays and abdominal CT scans were negative as well.

The only notable blood findings were a positive antigen for Epstein-Barr virus, a low platelet count (thrombocytopenia), an elevated C-reactive protein (an inflammatory marker), and an elevated procalcitonin—a biomarker that is released in response to bacterial infections.

Specialty lab testing

Considering the patient’s immunocompromised status and continued relapsing fevers, his blood was sent to a specialty lab for next-generation DNA sequencing. The specialty lab, Karius,  says it can identify over 1000 clinically relevant pathogens including bacteria, DNA viruses, fungi, and parasites from a single blood sample.

The DNA test results came back positive for Borrelia miyamotoi and were sent to the CDC for confirmation. The CDC confirmed the patient’s blood was positive for Borrelia miyamotoi and 100% identical to an isolate that had been previously collected from an Ixodes pacificus tick in Marin County. This indicates the patient acquired the infection in California.

Borrelia miyamotoi, first identified in Japan in 1995, is considered an emerging infectious disease in Asia, Europe and the United States.

A recent study found widespread evidence of Borrelia miyamotoi in human blood samples of people living in the northeastern United States. An earlier study found evidence of tick-borne relapsing fever (TBRF) Borrelia, including Borrelia miyamotoi in the blood of 26 out of 101 samples of residents of Mendocino County, California in the 1980s.

Another study found multiple species of relapsing fever Borrelia in blood samples drawn from patients in 16 out of 24 California counties. And a 13-year-long study found Borrelia miyamotoi in ticks found in 24 out of 48 counties in California (see map below).

Borrelia miyamotoi is transmitted to humans through the bite of infected blacklegged ticks. These are the same  hardbodied ticks (Ixodes scapularis, Ixodes pacificus) that transmit Lyme disease to humans and animals. Other types of North American tick-borne relapsing fever Borrelia (B. hermsii, B. turicatae, B. parkeri), are transmitted by soft-bodied ticks.

The symptoms of Borrelia miyamotoi disease are similar to those of other tick-borne illnesses, such as Lyme disease. But standard Lyme tests will be negative, making the diagnosis challenging.


According to the CDC, the main symptoms of TBRF are high fever, headache, muscle and joint pain. Fewer than 1 in 10 patients will develop a rash. Left untreated, the symptoms typically repeat, producing a telltale pattern of relapsing fever lasting 1-3 days, followed by 7-10 days without a fever, followed by another 1-3 days of fever.

The CDC website says: “Confirmation of a diagnosis relies on 1) the use of polymerase chain reaction (PCR) tests that detect DNA from the organism or 2) antibody-based tests. Both types of tests are under development and not widely commercially available but can be ordered from a limited number of CLIA-approved laboratories.”

Treatment for TBRF involves the use of antibiotics, such as doxycycline, amoxicillin or cefuroxime . In this case the man was given a 4-week course of doxycycline and achieved complete resolution of his symptoms. One month after completing antibiotics ,follow-up laboratory testing showed complete resolution of thrombocytopenia and normalization of inflammatory markers.

All tick-borne diseases are a significant health concern worldwide, particularly in areas where ticks are prevalent. These illnesses can present with a range of symptoms, some of which can be mysterious and difficult to diagnose.

While relapsing fever Borrelia has been detected in California before, this is the first CDC-confirmed case of Borrelia miyamotoi in California.  This case highlights the need for continued education and awareness of tick-borne diseases.

As with all tick-borne illnesses, prevention is key. To reduce the risk of tick bites, take precautions when spending time outdoors, such as pre-treating shoes and clothing with permethrin, using insect repellant on yourself, your children and your pets, and performing thorough tick checks after being outdoors.

LymeSci is written by Lonnie Marcum, a Licensed Physical Therapist and mother of a daughter with Lyme. She served two terms on a subcommittee of the federal Tick-Borne Disease Working Group. Follow her on Twitter: @LonnieRhea  Email her at:


Rubio LA, Kjemtrup AM, Marx GE, Cronan S, Kilonzo C, Saunders MEM, et al. Borrelia miyamotoi infection in immunocompromised man, California, USA, 2021. Emerg Infect Dis. 2023 May DOI: 10.3201/eid2905.221638

Padgett K, Bonilla D, Kjemtrup A, Vilcins I-M, Yoshimizu MH, Hui L, et al. (2014) Large Scale Spatial Risk and Comparative Prevalence of Borrelia miyamotoi and Borrelia burgdorferi Sensu Lato in Ixodes pacificus. PLoS ONE 9(10): e110853.

Additional Resources

Stanford: Tick-borne disease risk high in SF Bay Area

Yale: Tick-borne Borrelia miyamotoi widespread in northeastern US

LYME SCI: Infected ticks in California? It’s complicated.

LYME SCI: B. miyamotoi has been in California ticks for a long time

LYME SCI: Lyme-carrying ticks in West differ from their Eastern cousins

LYME SCI: How many “negative” Lyme tests are due to B. miyamotoi?

LYME SCI: Tick infection rates as high as 31% in some coastal areas of California

BALF: New interactive maps show where citizen scientists found infected ticks

For more:

And the question begging to be asked is: how many people with B. miyamotoi are falling through the cracks?  It isn’t even reportable to the CDC yet (which notoriously undercounts all things tick-borne-related).

For more:

This article points out the confusion with B. miyamotoi: 

  • many separate it from other tick-borne relapsing fevers
  • while it can cause relapsing fevers, it sometimes doesn’t
  • it appears to be the only TBRF transmitted from a hard bodied tick, unlike TBRF which is mainly transmitted from a soft bodied tick (I remain skeptical of this as ticks have repeatedly been found to transmit things they shouldn’t – just like they are found in places they shouldn’t be.)
  • symptoms often resemble Lyme disease
  • you can be infected with BOTH B. miyamotoi AND Lyme disease (as well as numerous other coinfections) which will complicate symptom presentation
  • testing for B. miyamotoi is just as abysmal as it is for Lyme/MSIDS:

Borrelia Miyamotoi Can Be Transmitted From Mother Ticks To Offspring



Lyme disease and Borrelia miyamotoi can be transmitted from a tick to a host and vice versa (horizontal transmission). B. miyamotoi can also be transmitted from the mother to their offspring (vertical transmission).

In their article Borrelia miyamotoi: A Comprehensive Review. Pathogens,” Cleveland and colleagues discuss Borrelia miyamotoi as an emerging tick-borne pathogen and and how it can be transmitted from a mother tick to their offspring.

Cleveland et al. reviewed the proposed vertical transmission of B. miyamotoi.¹

  • An adult female tick infected with B. miyamotoi lays eggs.
  • The larva hatch from these eggs infected with B. miyamotoi.
  • The larva, nymph and adult ticks remain infected.

Ticks can acquire B. miyamotoi after feeding on an infected tick – called horizontal transmission.

Cleveland et al. reviewed the proposed horizontal transmission of B. miyamoti.¹

  • The larva, nymph and adult ticks acquire B. miyamoti from feeding on an infected host.
  • The larva, nymph and adult ticks remain infected.

B. miyamotoi can be transmitted from infected ticks to naïve mice during the first 24 hours of feeding,” the authors wrote.

B. miyamotoi can be transmitted to mice initially through the salivary glands and subsequently transmitted through the midgut.

Concerns surrounding Borrelia miyamotoi

Shapiro and Wormser summarized the challenges associated with B. miyamotoi in the Journal of the American Medical Association.²

  • “This bacterium can be transmitted within the first 24 hours of tick attachment.”
  • “The probability of transmission increases with every day an infected tick is allowed to remain attached.”
  • While some patients with Lyme disease may exhibit a rash, “patients infected with B. miyamotoi in the United States typically do not have a rash.” But they may present with “a fever in conjunction with headache (96%), myalgia (84%), arthralgia (76%), and malaise/fatigue (82%).”
  • There are no diagnostic tests for B. miyamotoi infection that have been approved by the US Food and Drug Administration.
  • The fever may be relapsing.
  • “Laboratory abnormalities include leukopenia (51%) and thrombocytopenia (60%), which are rarely seen in Lyme disease.” [Editor’s note: These are also seen in Ehrlichia and Anaplasmosis.]
  • “Severely immunocompromised patients may develop chronic meningitis.”

Fortunately, doxycycline and amoxicillin have been shown to effectively treat B. miyamotoi infection in patients, including those who are immunocompromised.

Editor’s notes: Fevers are infrequent and often do not relapse. The laboratory abnormalities seen in B. miyamotoi are also seen in Ehrlichia and Anaplasmosis. Long-term outcome studies are needed.

CA Ticks Spread Lyme But That’s Not the Whole Story

If you find a tick bite from an Ixodes tick in California, it’s important to consider possible exposure to pathogens that cause more than Lyme disease

Originally published on 

The risk of contracting Lyme disease from a tick bite in California has been well-documented, though there is still a long way to go in educating health providers and the broader community in the exposure risk from a tick bite. TickReport’s surveillance of ticks from California (and Oregon and Washington) goes back as far as 2006 and has expanded in recent years.

What ticks are endemic (commonly and consistently found in wild populations) to California and other West Coast states?

That’s a big question, and there are a few dozen species from different genera or families. Many of those species are specialist feeders and—if everything goes “right” in their life cycle—they will only feed on certain wild mammals, birds, or lizards and will bite humans very rarely. That’s doesn’t mean that finding one of these “specialists” attached to ourselves or a family member is impossible: it’s just much less common (and a topic we’ll try to visit soon in another post).

Our surveillance shows that the majority (91.5%) of human or human-adjacent (dogs, cats, horses, etc) tick bites are caused by the following ticks:

  • Ixodes pacificus (“Western black-legged tick,” a close relative of the Deer tick in the Eastern U.S.)
  • Dermacentor variabilis (“American dog tick”)
  • Dermacentor occidentalis (“Pacific Coast tick”)
  • Dermacentor andersoni (“Rocky Mountain Wood tick”)
  • Ixodes spinipalpis
  • Ixodes angustus
What pathogens can these ticks transmit to humans?

Vector competence (the ability of a vector like a tick to transmit a given disease-causing pathogen) tends to run along genus lines, so species within the Ixodes genus tend to be able to transmit pathogens X and Y but not Z, while Dermacentor species tend to transmit Z but not X and Y.

The most common pathogen found in California ticks is Borrelia burgdorferi, which causes Lyme disease in humans and pets. But there’s more than Lyme in those hills! If you find a tick bite from an Ixodes tick in California, it’s also important to consider possible exposure to these pathogens:

  • Borrelia miyamotoi: a bacterium that can cause hard tick relapsing fever—sometimes called Borrelia miyamotoi disease.
  • Anaplasma phagocytophilum: a bacterium that can cause Human granulocyctic Anaplasmosis.
*For every two ticks we find infected with Borrelia burgdorferi (Lyme disease bacteria), we detect one (or more) of these other pathogens

It’s vital that both tick surveillance and diagnostic approaches keep these non-Lyme pathogens in mind. For every two ticks we find infected with Borrelia burgdorferi (Lyme disease bacteria), we detect one (or more) of these other pathogens, so be sure to resist Lyme Tunnel Vision when responding to a tick bite! Common diagnostic tests for Lyme disease have a specific focus on Lyme disease and will not detect infection by these other pathogens if present. Make sure you and your doctor are considering the whole story of a tick bite.

To learn more about the pathogens we find in West Coast ticks, browse our real-time testing data at If you find and remove a tick, arrange for fast and accurate identification and testing at
The above material is provided for information purposes only. The material (a) is not nor should be considered, or used as a substitute for, medical advice, diagnosis, or treatment, nor (b) does it necessarily represent endorsement by or an official position of Global Lyme Alliance, Inc. or any of its directors, officers, advisors or volunteers. Advice on the testing, treatment or care of an individual patient should be obtained through consultation with a physician who has examined that patient or is familiar with that patient’s medical history. 

Paul Killinger oversees tick surveillance and pathogen testing at the TickReport testing lab in Amherst, Massachusetts. He has led the lab's public health education and outreach since 2018.

Meningoencephalitis Due to Borrelia Miyamotoi

Meningoencephalitis due to Borrelia miyamotoi

In their case report, Gandhi and colleagues, describe an immunocompetent patient who developed acute-onset, progressive encephalopathy due to an infection with Borrelia miyamotoi.

By Dr. Daniel Cameron

A 73-year-old man was admitted to the hospital with a 16-day history of confusion and intermittent headaches. He was an avid gardener and reportedly had tick bites in the past but none that he noticed in the weeks prior to his symptoms.

Initially, he developed “right-sided facial droop and associated numbness, confusion, and word-finding difficulties,” the authors write in the article “Borrelia miyamotoi Meningoencephalitis in an Immunocompetent Patient.”¹

His symptoms, which had improved, were attributed to a mini-stroke.

However, “Over the next 2 weeks, he continued to feel numbness in his right face and developed worsening confusion, intermittent headaches, and excessive fatigue; he was afebrile throughout this time.”¹

The patient tested positive for Lyme disease by EIA but negative by Western blot.

He was “empirically treated with intravenous ceftriaxone for treatment of presumed Lyme meningoencephalitis, and his mental status rapidly improved,” the authors write.

READ MORE: What is Borrelia miyamotoi?

When repeat testing for Lyme disease was negative by Western blot, clinicians considered another tick-borne infection – Borrelia miyamotoi.

The man tested positive for B. miyamotoi and made a “nearly full neurological recovery with only residual intermittent right facial numbness” after anti-Borrelia antibiotic treatment.

The authors conclude:

  • “Our case therefore highlights the need to include B. miyamotoi disease in the differential diagnosis for any patient who presents with acute onset, progressive encephalopathy with culture-negative CSF in B. miyamotoi–endemic regions, not just those who are immunocompromised.”
  • “Our case highlights the importance of considering B. miyamotoi in clinically suspicious cases of meningoencephalitis, including when B. burgdorferi EIA results are positive but the WB is negative.”

Could A Major Chronic Infection Be Underlying ME/CFS?

B. miyamotoi is a prime candidate to be the major chronic infection underlying ME/CFS”

The fifth in a series of blogs reporting on the 2022 IACFS/ME Conference focuses on an intriguing possibility: that heretofore unknown infection is present in most people with chronic fatigue syndrome (ME/CFS).

Talk about a jaw-dropping statement. With the exception of Dr. Chia’s work on enteroviruses and Ariza’s work on the Epstein-Barr virus, most researchers have pretty much given up on finding “the chronic infection” underlying ME/CFS. Repeated failures to find evidence of a pathogen have led to the conclusion that while ME/CFS can be triggered by a variety of infection, the pathogen is likely long gone. With the emergence of long COVID, though, the idea of viral persistence has caught hold and the question is back – could a persistent pathogen or bits of a pathogen be causing ME/CFS?

It got a bit more interesting when De Meirleir looked where no one has looked before –  at tick-borne pathogens and at ones other than the Lyme disease-causing bug (Borrelia) at that. Plus, he used a new testing approach using bacteriophages to find them.

My numbers may not be correct, but the gist is that in this rather large study, a very large percentage of ME/CFS patients tested positive for B. miyamotoi while few of the healthy controls did. My jumbled notes stated that 81% of people with ME/CFS tested positive while 20% of the healthy controls did.  (See link for article)



Very interesting article.  Important gold nugget:

…he focused on the ileocecal valve that separates the small intestine from the large intestine. I didn’t write down the possible connection between B. miyamotoi and the ileocecal valve, but the last time I remember hearing about it was decades ago from Dr. Cheney who pointed to a spot on my lower right abdomen which he said was almost always painful in ME/CFS. (Mine is).