After 6 of about 9,000 blood samples produced “unusual results,” scientists at the Mayo Clinic thought they might be looking at a new cause of Lyme disease. DNA sequencing showed that a new bacterium was the cause.
Provisionally named Borrelia mayonii (B mayonii), the bacterium is closely related to Borrelia burgdorferi (B burgdorferi), which until now was the only bacterium believed to cause Lyme disease in North America. Borrelia mayonii causes fever, headache, rash, and neck pain in the early stages and arthritis in later stages. Unlike B burgdorferi, B mayonii is also associated with nausea, vomiting, and a higher concentration of bacteria in blood. Instead of the famous “bull’s-eye rash,” B mayonii produces diffuse rashes.
The researchers believe, like B burgdorferi, B mayonii is transmitted by the bite of an infected deer tick. It has been identified in ticks collected in at least 2 counties in northwestern Minnesota. The patients were most likely infected in north central Minnesota and western Wisconsin; the CDC cautions that the infected ticks are found throughout both states. So far the new species is found only in the upper Midwest. Blood samples from residents of 43 other states with suspected tick-borne disease did not carry the bacterium.
Patients were treated successfully with the antibiotics used to treat Lyme disease caused by B burgdorferi. The CDC recommends that health care providers for patients infected by B mayonii follow the antibiotic regimen described by the Infectious Diseases Society of America.