They have named the bacteria Borrelia mayonii, after the two brothers, William and James Mayo, who founded the Rochester, Minnesota, clinic. Before this finding, which was published Monday in the journal Lancet Infectious Diseases, the only species believed to cause Lyme disease in North America was Borrelia burgdorferi.
Lyme disease is a potentially serious illness that is transmitted to humans through the bite of infected blacklegged ticks (also known as deer ticks and bear ticks). It is the most common tick-borne disease in the United States. Cases are heavily concentrated in 14 states, including the Upper Midwestern states of Minnesota and Wisconsin. In 2014, Minnesota had 896 confirmed cases of the disease and 520 probable cases, according to the Minnesota Department of Health (MDH).
Mayo researchers first suspected that a new bacterium might be involved in Lyme disease after analyzing blood samples taken from 9,000 people with symptoms of the illness. Using a testing method called polymerase chain reaction (PCR), they noticed that six of the samples — ones collected in Minnesota, Wisconsin and North Dakota — had produced an atypical result. In collaboration with the Centers for Disease Control and Prevention (CDC), the Mayo researchers conducted additional tests on those six samples, which revealed a bacterium genetically distinct from B. burdorferi.
Over the past decade, the Mayo Clinic has used PCR to test more than 100,000 patient specimens from across the country, but it’s only recently that it has detected this new species of bacteria — and only in patients in the Upper Midwest.
Furthermore, since the discovery of B. mayonii, researchers have analyzed approximately 25,000 additional blood samples taken from people with suspected cases of Lyme disease in 42 other states, including in the Northeast and Mid-Atlantic, where the disease is common. They found no evidence of the B. mayonii in any of those samples.
“It could be that it newly emerged in the Upper Midwest, or it could be that it was present at lower levels for a longer period of time and it’s only recently come to a level that’s high enough for us to detect it,” says Dr. Bobbi Pritt, the study’s lead author and director of the Mayo Clinic’s Clinical Parasitology Laboratory, in a video released with the study.
Similar, but not identical, symptoms
B. mayonii is most likely transmitted to humans the same way as B. burgdorferi: through the bite of a blacklegged tick. Pritt and her colleagues tested about 600 blacklegged ticks and found that 3 percent of them tested positive for B. mayonii.
Both bacteria species appear to produce similar Lyme disease symptoms: fever, headache, rash, neck pain and, in later stages, arthritis. But — based on the limited information collected from the six patients — there seems to be two notable differences. Patients whose disease is caused by B. mayonii are more likely to have nausea and vomiting, and their rash tends to be more diffuse.
“It wasn’t the classic bull’s eye rash that you see with Lyme disease caused by Borrelia burgdorferi, and therefore physicians may not always suspect this infection right away,” says Pritt.
“It’s important to note,” she adds, “that two of our six patients were hospitalized, so this is not a benign infection.”
Still, the B. mayonii infection does not appear to be more serious than the one caused by B. burgdorferi. All six patients were successfully treated with antibiotics.
The Mayo researchers are working with the CDC, the Minnesota Department of Health and the health departments of Wisconsin and North Dakota to develop a better understanding of B. mayonii and the specific form of Lyme disease it produces.
In the meantime, Minnesotans should continue to follow the CDC’s recommendations for limiting the risk of tick bites and tickborne diseases:
- Avoid wooded and brushy areas with high grass and leaf litter.
- Use insect repellent when outdoors
- Use products that contain permethrin on clothing.
- Bathe or shower as soon as possible after coming indoors to wash off and more easily find ticks.
- Conduct a full-body tick check after spending time outdoors.
- Examine gear and pets, as ticks can come into the home on these and later attach to people.
- You don’t need to take these precautions just yet. But get ready. Minnesota’s tick season starts in May and continues through October.
You don’t need to take these precautions just yet. But get ready. Minnnesota’s tick season starts in May and continues through October.