Mosquitoes may be receiving all the attention amid the Zika virus epidemic, but they are hardly the only disease vectors to worry about. Researchers at the Mayo Clinic in Rochester, Minn., have discovered a new species of tick-borne bacteria that causes Lyme disease.
The new species, provisionally named Borrelia mayonii, after the clinic, been found only in the Upper Midwest but may be present elsewhere.
Six patients with the infection were identified by the researchers. The patients had symptoms similar to, but not precisely the same as, those caused by Borrelia burgdorferi, until now the only species known to cause Lyme disease in North America.
Lyme disease was diagnosed in the patients with available tests. But available diagnostic screens may be missing others infected with the newly discovered bacteria, the scientists acknowledged.
Dr. Bobbi Pritt, the medical director of the microbiology laboratory at the Mayo Clinic, where the new strain was first detected, recommended that patients with exposure to ticks in Minnesota and Wisconsin receive antibody and polymerase chain reaction testing to detect B. mayonii if they are concerned about Lyme infection but do not have the telltale bull’s-eye rash.
Only one of the six patients had the bull’s-eye rash that is Lyme’s signature, present in 70 percent to 80 percent of reported cases. Three patients had a rash that was more spread out, Pritt said.
The new strain apparently adds nausea and vomiting to the list of typical Lyme symptoms, which include fever, headache and neck pain. B. mayonii patients also had a higher-than-expected concentration of bacteria in their blood.
Fortunately, the antibiotic treatment normally used to treat Lyme disease appears to be effective against B. mayonii, Pritt said.
In the summer of 2013, a technician in Pritt’s lab noticed some unusual results from a genetic screen of a patient’s bacterial infection. The test suggested Lyme disease, but a closer analysis found a new species of bacteria causing the condition.
It is not yet clear where B. mayonii came from, Pritt said, though it does not seem to have recently diverged from B. burgdorferi. It may be that the species has always been present, but was picked up only with better detection tools, or that the new bacteria are increasing for some reason.
“We hope to be able to answer that with more studies,” Pritt said.
In Europe, Lyme disease is caused by multiple pathogenic species of Borrelia, said Per-Eric Lindgren, a professor of medical microbiology at Linkoping University in Sweden.
While scientists were already aware that there were several possible causes of Lyme disease, the discovery of the first Borrelia species in more than a decade is “really exciting and interesting,” said Lindgren, who wrote a commentary accompanying the report in the Lancet Infectious Diseases.
Although the six patients at the Mayo Clinic received the diagnoses with typical tests, he said, “normally you’re only able to detect what you are looking for.” Other cases are probably being missed, Lindgren added: “It’s very likely you could make the diagnostic tools better.”
Field studies in Minnesota have shown that one-third to one-half of adult ticks, and one in five young ticks, called nymphs, carry B. burgdorferi, the previously known bacteria. Only 1 percent to 4 percent carry B. mayonii, said Dave Neitzel, the supervisor of the vector-borne disease unit at the Minnesota Department of Health.
“This is just another great reason to protect yourself against ticks,” he said.
To protect against tick-borne illnesses, people should wear repellents and check their skin for black specks after spending time outdoors, particularly in wooded areas and during the late spring and early summer months when nymphs are present.
The nymphs are smaller than the adults and easier to miss on the skin, Neitzel said.
If a tick is removed within the first 24 to 48 hours, it is unlikely to cause disease.
“The sooner you get that tick off of your body, the better,” he said.
“You don’t have to get too many ticks on you before you find one that’s infected with something.” Pritt said she was now far more cautious outdoors.
“If you’ve ever looked at an idyllic picture of a beautiful meadow with flowers — I look at it and think about all the ticks in there,” she said.