ATLANTA, Feb. 9 (UPI) -- Scientists at the Mayo Clinic and the U.S. Centers for Disease Control and Prevention identified a second tick-borne bacteria that causes Lyme disease, according to a new report.
The bacteria, Borrelia mayonii, was identified in ticks in Minnesota, Wisconsin and North Dakota after scientists tested six people there thought to have Lyme disease despite differences in their symptoms.
Although several types of bacteria are known to cause the disease in other parts of the world, Borrelia burgdorferi was, until now, the only one known to infect humans in North America.
Lyme disease can cause fever, headache, rash and neck pain within days of infection, and causes arthritis within weeks, though the new infection may also include nausea, vomiting, diffuse rashes instead of the 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 percent of black-legged ticks carry the new species of bacteria, while scientists said the older species can be found in 30 to 40 percent of black-legged ticks, which can carry both forms of the bacteria. Each year, 300,000 people are infected with Lyme disease, 96 percent 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," Dr. Jeannine Petersen, 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."
Researchers involved in the study, published in The Lancet Infectious Diseases, 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. The continued research seems even more important because the second form of Lyme disease had not been found in thousands of samples collected before 2013.
"Maybe it infected woodchucks and no one ever tested them," Dr. Bobbi Pritt, a researcher at the Mayo Clinic, told NPR. "But what we can say is, it's a species that no one has ever described before and it's clearly infecting patients."