A second bacterium that causes Lyme disease in North America has been identified by researchers at the Mayo Clinic and U.S. Centers for Disease Control and Prevention, according to a report published Feb. 5 in The Lancet Infectious Diseases.
Several bacteria cause Lyme disease in other parts of the world, but until recently, only the tick-borne Borrelia burgdorferi was known to infect humans in North America. The newly discovered Borrelia mayonii, which also is tick-borne, was identified in ticks in Minnesota, Wisconsin and North Dakota after six people were thought to have Lyme disease despite symptom differences.
“We detected this result, which was positive, but it was clearly different from what we would have expected for Borrelia burgdorferi, which at that time was the only known cause of Lyme disease in the U.S.,” Bobbi Pritt, PhD, a microbiologist at the Mayo Clinic, said in an NPR report written by Rae Ellen Bichell.
Lyme disease can cause fever, headache, rash and neck pain within days of infection, and causes arthritis within weeks. The new infection may also include nausea, vomiting, diffuse rashes instead of the well-known single “bull’s-eye” rash, and a higher concentration of bacteria in the blood. Current tests and treatment are effective against the new form of the disease, the CDC said in a press release.
About 3% of the black-legged tick Ixodes scapularis carry the new species of bacteria, while researchers said the older species can be found in 30% to 40% of black-legged ticks, which can carry both forms of the bacteria. Each year, 300,000 people are infected with Lyme disease, 96% of whom live in the Northeast and Midwest,according to the CDC. “At this time there is no evidence that B. mayonii is present outside of the Upper Midwest,” Jeannine Petersen, PhD, a researcher at the CDC, told CBS News. “However, people who live in areas where black-legged ticks are common should continue to take precautions.”
The black legged tick, also known as the deer tick, has been spreading its range, according to the NPR report. “Lots of people are encountering ticks where they didn’t encounter them 20 years ago,” Rebecca Eisen, PhD, a research biologist with the Centers for Disease Control and Prevention, said in the NPR article. “It’s a living organism, so the range of the tick changes, and so the likelihood of people encountering these ticks changes.”
Researchers involved in the study have tested more than 100,000 Lyme disease specimens from patients collected between 2003 and 2014. Among these, Mayo Clinic researchers found six with bacteria different from the other patients, who also reported different symptoms. Five had fever when they sought treatment, four had a diffuse rash, three had neurological symptoms that included difficulty being woken and vision disturbances, and another had pain and swelling in the knee.
Scientists at Mayo and the CDC analyzed DNA sequences from the bacteria, finding they were a different species than typically causes Lyme disease in the United States. The new species was found among 9,000 blood samples from Minnesota, Wisconsin and North Dakota residents thought to have Lyme disease between 2012 and 2014. Mayo Clinic and CDC started a large study of tick-borne disease in 2015 to test more than 30,000 clinical specimens from patients with tick-borne diseases.
Photo courtesy of U.S. Centers for Disease Control and Prevention.
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