Lyme Disease, Part 2: Borrelia mayonii–A New Cause of Lyme Disease in Upper Midwest

Expires May 2025

Bobbi Pritt, M.D.

Lyme disease is the most common vector-borne illness in the United States and Europe. It is caused primarily by Borrelia burgdorferi in the United States, while B. burgdorferi, B. afzelii, and B. garinii cause Lyme disease in Europe. In 2013, a patient was hospitalized and tested for multiple diseases, including Lyme disease. Using PCR and melting curve analysis, a new species of Borrelia was identified. Using prospective and retrospective studies, a total of six cases of Lyme disease caused by this new species, Borrelia mayonii, were confirmed.


Bobbi Pritt, M.D., is Director of the Clinical Parasitology Laboratory at Mayo Clinic in Rochester.


Our speaker for this program is Dr. Bobbi Pritt, Director of the Clinical Parasitology Laboratory at Mayo Clinic, Rochester, Minnesota. Dr. Pritt introduces a new species of Borrelia as a cause of Lyme disease.Welcome to Mayo Medical Laboratories Hot Topics. These presentations provide short discussion of current topics and may be helpful to you in your practice.

Thank you for that introduction, Cara. It is my pleasure to discuss our discovery of a new organism that causes Lyme disease in the upper Midwestern United States. My colleague, Dr. Elli Theel, has already provided an overview of Lyme disease in part I of this series, so today I will be building upon the material she has delivered.


Before I begin, I’d like to mention that I have no disclosures for this presentation.

Utilization Management

I do have a utilization message. As we go through this presentation, please consider the important points regarding testing for Lyme disease due to Borrelia mayonii. Ask yourself, how and when are serologic and PCR testing going to be used in your practice, keeping in mind that this organism has only been found in the upper Midwestern United States? And, also, it’s always important to ask, how will results impact patient management?


So with that I will move on to my objectives, which for today are that participants should be able to, name the organisms responsible for Lyme disease in the United States. Describe common signs and symptoms of Lyme disease. And discuss the unique clinical features of Borrelia mayonii infection compared to other causes of Lyme disease.

Lyme Disease

So to start, let’s first review a little bit about Lyme disease. It is caused by tick-transmitted bacteria in the Borrelia burgdorferi sensu lato complex. Borrelia burgdorferi sensu stricto is the primary cause of Lyme disease in the United States. For simplicity, I will simply refer to this organism as Borrelia burgdorferi. In Europe, Borrelia afzelii, Borrelia garinii, and Borrelia burgdorferi are the causes of Lyme disease.

I’d like to point out that Borrelia species actually fall into 2 large groups–those in the Borrelia burgdorferi sensu lato complex, and those in the relapsing fever group. Today, I’ll only be discussing the Borrelia species in the sensu lato complex that cause Lyme disease in humans.

Lyme Epidemiology

It is important to understand the epidemiology of Lyme disease, since it is an important disease in some parts of the world. In fact, it is the most common vector-borne illness in the United States and Europe! It doesn’t occur in all parts of the United States, but is concentrated in the north east and upper Midwestern states, as shown on this map from the CDC. Approximately 36,000 cases of Lyme disease are reported to the CDC every year, and it is estimated that the actual number of cases is 10 times greater than this.

Lyme Disease Diagnosis

Lyme disease is a vector-borne disease, being transmitted through the bite of infected black-legged ticks, also known as a deer ticks. In the United States, Ixodes scapularis is the primary vector, while Ixodes pacificus causes a smaller number of cases in the Pacific states.

Lyme Disease PCR

The diagnosis of Lyme disease is primarily based on the patient’s clinical presentation and their exposure to black-legged ticks in areas where Lyme disease is endemic. As Dr. Theel mentioned in part I of this series, patients with a classic erythema migrans (EM) rash in this setting should be treated for presumptive Lyme disease. Serologic testing is useful when erythema migrans is not present, and is the test of choice for detection of Lyme disease. The CDC recommends a 2-tiered testing approach using tests approved by the Food and Drug Administration (FDA).

Lyme PCR–Targeting the Plasminogen-Binding Protein gene (oppA1)

Lyme PCR may also be available in reference and public health laboratories. It can be a useful adjunctive test to serology in some settings, since it allows for direct detection of the infectious organisms, compared to serology, which detects the host’s immune response to the organism. Also, it may be positive during acute stages of illness, before the development of antibodies, which can take a week or more.

However, it has relatively low sensitivity for detecting the spirochetes that cause Lyme disease. Blood is only positive in only 50% of cases with erythema migrans and CSF is positive only one-third of patients with early neuroborreliosis.

Therefore, it is considered to be an adjunctive test and should not be used routinely for Lyme disease diagnosis. Mayo Medical Laboratories offers a real-time Lyme disease PCR assay, which we perform on blood, CSF, synovial fluid, and tissue.

The PCR assay that we use targets the plasminogen binding protein gene, oppA1. It detects all of the known species that cause human Lyme disease, and can differentiate Borrelia burgdorferi from Borrelia afzelii and Borrelia garinii using a postamplification method called melting temperature analysis. You can see on the figure on this page how different peaks are formed when DNA from the different species are present.

How the Story Began…

With this introduction, I will now move into the story of how Borrelia mayonii was discovered.

To do so, I will first set the national stage, focusing on Minnesota and Wisconsin, the 2 states shown in red on this map.

It was the summer of 2013 when a 10-year old boy from northwestern Minnesota presented with fever, headache, neck pain, myalgia, nausea and vomiting, and a diffuse rash. As shown here. He also had profound somnolence. These symptoms were so severe, that he was hospitalized for 4 days. On further history, the physicians learned that he had spent the week prior in Spooner, Wisconsin, where he was exposed to multiple ticks. This presentation and history prompted the ordering of multiple tests including Lyme PCR.

Lyme PCR–EDTA Whole Blood Specimen

This next slide shows the results of the PCR that was performed on a whole blood specimen from this patient. While normally the only peaks seen are in the temperature ranges of the known causes of Lyme disease, this patient’s specimen produced an intermediate peak, outside of the expected melting temperature ranges.

Patient History Continued

The patient was treated with ceftriaxone for 1 day, followed by 21 days of amoxicillin and fortunately he made a complete recovery. However, we are meanwhile left with an interesting situation where we had an atypical Lyme PCR result that wasn’t matching up with the known causes of Lyme in the United States and Europe. Therefore we needed to investigate further.

More Cases Identified

As we were investigating this case, we began to identify more cases. First we had another case the following month, in July of 2013, of an 11-year-old boy from WI, whose PCR results from whole blood also showed that same atypical melting temperature peak. This prompted us to perform a retrospective review of all atypical cases that might have occurred since 2003 when we first began to offer this PCR assay, and this allowed us to identify 2 additional cases:

One case was a 65-year-old male from North Dakota (with exposure to ticks in Minnesota), who had a positive PCR test on a whole blood specimen during July of 2012.

The second case was a synovial fluid specimen that was positive from a 21-year-old woman living in Wisconsin. This case had been detected by our lab at Mayo Clinic Eau Claire in June 2013.

Further Studies

At this point, we realized that we were dealing with a series of cases that needed further investigation. Therefore, we collaborated with the Minnesota and Wisconsin state health departments and the CDC. And sent blood from our 2 recent patients for culture and sequencing at the CDC, and we also performed these studies at Mayo Clinic.


This next slide shows the results of our studies. On the left is an image of 1 patient’s blood specimen as seen using dark-field microscopy. Note that there is a single spirochete that is present in this image, as denoted by the arrow. There were approximately 2 spirochetes in every 70 high-power fields that we examined, after diluting the specimen 1:10 with normal saline. This equates to approximately 85,000 spirochetes/mL of blood.

Our cultures were also positive from 2 of the blood specimens. And, as you can see here in this movie, these spirochetes growing in culture. And, you can note their classic cork-screw motility.

We also performed an extensive genetic analysis on the DNA that we could amplify from this organism, looking at 8 different housekeeping genes. The phylogenetic analysis is shown here for the 2 isolates grown from blood. Note that the Borrelia burgdorferi isolates are all shown at the top, while the 2 patient isolates, as indicated by the arrow, are clearly removed from them and other species.

Multi-Locus Sequence Analysis (MLSA)

Lastly, we performed a multilocus sequence analysis that had previously been used for defining genospecies in the Borrelia burgdorferi sensu lato complex. From this analysis, we observed that the highest pairwise similarity was to Borrelia burgdorferi, with an approximate 95% similarity. And the threshold for separating genospecies using this analysis is anything that is 98.3% similar or less. Therefore, we were able to confirm that we identified a novel Borrelia genospecies. We have proposed the name, Borrelia mayonii, for this new organism, in honor of the Mayo brothers who founded Mayo Clinic.

Clinical Features of the 6 Patients

So as of 2014, we had identified a total of 6 cases. They ranged in age from 10 to 67, and the majority of patients were male; of these 6 patients, 5 presented with an acute febrile illness. Also, this was not a benign illness, and 3 had potential neurologic involvement, including confused speech, profound somnolence, and visual difficulties. Interestingly, 4 patients had a rash, but only 1 rash was typical of an erythema migrans rash. Instead, the rashes were more diffuse, like the image of the boy shown here. We also had 1 patient with joint swelling and pain. All of our patients reported exposure to ticks or tick habitat in Minnesota or Wisconsin, although not all patients actually recalled getting a tick bite. Finally, 5 of the 6 patients recovered with antibiotic therapy. But the patient with joint involvement continued to have residual joint pain for more than a year after the initial diagnosis.

We were able to obtain serologic test results for 5 of our 6 patients, which was also very helpful in understanding how this disease could be diagnosed. We observed that standard serologic testing was positive for patients tested at least 3 days after illness onset.

But patients tested earlier than 3 days did not always have a detectable serologic response. As I mentioned before, this is a known limitation of Lyme disease serology and, therefore, not a surprising finding. Also, most patients had a detectable IgM response by immunoblot testing. But not all patients developed a detectable IgG immunoblot response, even when tested more than a month after illness onset. This may be due to the fact that all of our patients received early antibiotic therapy. However, it also may be that the standard commercial immunoblot tests for Borrelia burgdorferi are not always capable of detecting IgG antibodies formed against Borrelia mayonii. Therefore, having an immunoblot assay specifically for Borrelia mayonii may be helpful, and we are currently working on developing one. So with this history of our discovery process, I’d now like to summarize the major findings and conclusions from our study.

Finding number 1: Borrelia mayonii causes Lyme disease in the upper Midwest, with production of signs and symptoms of traditional Lyme disease, as well as some unique features. Interestingly, it was not detected in patients before 2012, which may indicate that it is newly emergent in this area. Also, it was not found in any patients outside of the upper Midwest.

This was despite the fact that we had tested nearly 25,000 specimens from patients outside of the Midwest, including samples from many of the labs shown on this map as blue dots. And you’ll notice that many of the labs on this map are located in the northeast, where Lyme disease due to Borrelia burgdorferi is very prevalent. However, none of the specimens submitted from these labs were positive for Borrelia mayonii. So, it appears that this new organism is geographically restricted to the upper Midwest.

Finding number 2: Patients with Borrelia mayonii infection detected to date have had more severe disease than Lyme disease caused by Borrelia burgdorferi, including 3 patients with potential neurologic involvement and 2 patients who were so sick that they were hospitalized. However, given that we have only detected 6 patients so far, we will need more studies to learn about human infections with Borrelia mayonii.

Finding number 3: The rashes were more diffuse and only 1 of our 4 patients had a rash with the classic erythema migrans presentation. Instead, rashes involved the face, trunk, extremities as seen in this picture from our first case, and may even have involved the palms and soles of 1 patient.

Finding number 4: Borrelia mayonii has been found predominantly in whole blood specimens. And this is unusual since blood is not usually a good source for detecting Borrelia burgdorferi DNA. In fact, historically, less than 0.1% of blood specimens have tested positive for Borrelia burgdorferi. However, high levels of spirochetemia were observed with Borrelia mayonii, with significantly higher amounts of organism DNA than what is seen with Borrelia burgdorferi infection. Therefore, PCR is likely a good test for detecting acute Borrelia mayonii infection, and could be used in conjunction with standard serologic testing.

Finding number 5: Finally, Borrelia mayonii DNA was also detected in approximately 3% of 658 Ixodes scapularis ticks collected in 2 counties in Wisconsin. Therefore, we believe that this is the likely tick vector for Borrelia mayonii.

Published Findings

Our findings were recently published in Lancet ID, so you can read the article if you’d like more of these details.


This last slide shows the list of all of our collaborators who made this work possible. It was a group effort, with contributions from many individuals at the Mayo Clinic, public health laboratories, and state universities.

Thank you for joining me today to learn more about Borrelia mayonii.

MCL Education

This post was developed by our Education and Technical Publications Team.