Borrelia mayonii: A Rare Cause of Lyme Disease
Can Lyme disease be caused by more than one bacterium? Yes. Although Borrelia burgdorferi causes the vast majority of Lyme disease cases in North America, another species—Borrelia mayonii—can also cause Lyme disease in humans.
First identified in 2016, Borrelia mayonii is transmitted by the same black-legged tick (Ixodes scapularis) that spreads classic Lyme disease. Although infections remain rare, recent surveillance suggests the bacterium may be expanding beyond its originally recognized geographic range.
Most patients develop symptoms similar to classic Lyme disease, and early treatment with doxycycline remains effective. As surveillance improves, physicians may recognize additional cases and better define the clinical spectrum of this emerging Lyme disease bacterium.
What Is Borrelia mayonii?
Borrelia mayonii is a member of the Borrelia burgdorferi sensu lato complex, the group of bacteria responsible for Lyme disease.
Researchers first identified the organism after investigating patients from the Upper Midwest who had Lyme disease but whose laboratory findings differed from those typically seen with Borrelia burgdorferi. Subsequent studies confirmed that Borrelia mayonii represents a distinct species capable of causing human Lyme disease.
Like Borrelia burgdorferi, it is transmitted by black-legged ticks and responds to the same antibiotic therapy.
How Does It Compare With Classic Lyme Disease?
Most reported patients develop symptoms that resemble classic Lyme disease, including:
- Fever
- Headache
- Muscle and joint pain
- Fatigue
- Skin rash
Early reports suggest that some patients may have higher numbers of bacteria circulating in the bloodstream and more prominent systemic symptoms. However, relatively few human cases have been described, and researchers are still defining whether meaningful clinical differences exist.
At present, physicians should recognize that Borrelia mayonii behaves much like other Lyme disease bacteria and should be considered another potential cause of Lyme borreliosis.
Where Has Borrelia mayonii Been Found?
When Borrelia mayonii was first described, nearly all recognized infections occurred in Minnesota and Wisconsin.
More recently, public health investigators documented the first locally acquired human infection and infected ticks in New York State. Investigators identified both an infected patient and multiple infected black-legged ticks collected from the patient’s property, providing evidence of localized transmission.
Although these findings suggest that the bacterium may be expanding beyond its previously recognized range, Borrelia mayonii remains an uncommon cause of Lyme disease.
What Does This Mean for Patients?
The discovery of additional Lyme disease bacteria should not alarm patients.
Instead, it highlights the importance of continued surveillance and reminds clinicians that Lyme disease can be caused by more than one Borrelia species.
Fortunately, the same preventive measures remain effective:
- Avoid tick bites whenever possible.
- Perform careful tick checks after outdoor activities.
- Remove attached ticks promptly.
- Seek medical evaluation if symptoms develop following a tick bite.
Early diagnosis and treatment continue to provide the best opportunity for recovery.
Clinical Perspective
The discovery of Borrelia mayonii reminds us that Lyme disease is more diverse than once believed.
As surveillance improves, clinicians may identify additional Borrelia species and other emerging tick-borne pathogens. Fortunately, Borrelia mayonii remains rare, and current antibiotic therapy appears to be effective.
For patients, the key message remains unchanged: preventing tick bites, recognizing early symptoms, and obtaining prompt treatment continue to be the most important steps in reducing the risk of complications.
Frequently Asked Questions
What is Borrelia mayonii?
Borrelia mayonii is a rare bacterium that causes Lyme disease and is transmitted by black-legged ticks.
Is Borrelia mayonii different from Borrelia burgdorferi?
Yes. They are different species of Lyme disease bacteria, although they cause many similar symptoms and are treated with the same antibiotics.
Has Borrelia mayonii been found outside the Midwest?
Yes. Public health investigators recently documented the first locally acquired human infection and infected ticks in New York State, suggesting localized transmission outside its previously recognized range.
Can doxycycline treat Borrelia mayonii?
Yes. Reported patients have responded well to standard Lyme disease treatment, including doxycycline.
Related Articles
- Lyme Disease Symptoms
- Tick-Borne Diseases
- Anaplasmosis
- What to Do After a Tick Bite
- Lyme Disease Testing
References
- Pritt BS, Mead PS, Johnson DKH, et al. Identification of a novel pathogenic Borrelia species causing Lyme borreliosis with unusually high spirochaetaemia: a descriptive study. Lancet Infect Dis. 2016;16(5):556-564.
- Pritt BS, Respicio-Kingry LB, Sloan LM, et al. Borrelia mayonii sp. nov., a member of the Borrelia burgdorferi sensu lato complex, detected in patients and ticks in the upper Midwestern United States. Int J Syst Evol Microbiol. 2016;66(11):4878-4880.
- Nafiz TN, Prusinski MA, Gubbala S, et al. Notes from the Field: Borrelia mayonii Lyme Disease — New York, 2025. MMWR Morb Mortal Wkly Rep. 2026;75(21):271-272.
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
