Mayo Clinic researchers have discovered a new bacterium that's likely spread by the deer tick. The flu-like disease it causes can be quite serious in people with weakened immune systems.
Scientists aren't sure how this new species of Ehrlichia spread to the tick population. It hasn't been found anywhere else in the United States, and its closest relative is a tick-borne disease found in Eastern Europe and Asia.
So far 25 people from Minnesota, Wisconsin and South Dakota have had confirmed infections from the bacteria.
The discovery first came to light two years ago, when lab technician Carol Werner was doing some routine disease testing at an Eau Claire hospital and noticed something odd.
While none of the three tick-borne diseases she was testing for were present in a patient's blood sample, something that looked very similar was evident on her computer-generated graph.
"There was a peak in an unusual, unexpected place," said Werner, who is now retired.
Werner thought it might be a faulty result, so she ran the test again. When the same result came back, she became excited and called her supervisor.
"I said, 'Whoa. Look at this result. It's something different,'" she recalled.
The hospital lab in Eau Claire didn't have sophisticated DNA analysis equipment to identify the source of the odd result. So it sent the sample to the Mayo Clinic in Rochester.
Mayo's genetic testing revealed that the blood sample contained a new species of Ehrlichia bacteria, said Dr. Bobbi Pritt, a microbiologist at Mayo and director of the Clinical Parasitology and Virology Laboratories.
"This does look like it is a new bacterium never described before in the world," Pritt said.
Two other species of Ehrlichia known to exist in the United States cause a feverish illness in humans called ehrlichiosis. One species resides in ticks found mainly in Southern states. The other species affects residents exposed to ticks the Northeast and some Midwestern states.
But the Upper Midwest has never been a reservoir for either of those bacteria, which makes this new discovery all the more surprising, Pritt said.
"Notably, ehrlichiosis due to any cause was not thought to occur in Minnesota and Wisconsin, which is where all of our cases have been identified to date," she said. "So not only is this a new organism, but it's a relatively new disease for these two states."
David Burkinshaw, of Danbury, Wis., is just the second confirmed patient to contract the new bacterium. He became sick in July of 2009. His symptoms started with a sudden fever.
"I just felt really, really ill, achy, almost flu-like, I guess you would say," said Burkinshaw, 25. "It made me feel pretty miserable, I do remember that."
Burkinshaw was hospitalized for several days. He said his doctors ran every test they could think of because as a double-lung transplant recipient, he's particularly vulnerable to infections.
When he finally learned that a deer tick probably caused his illness, Burkinshaw, who lives deep in the woods, was relieved that his condition could be treated. After receiving antibiotics, he made a full recovery.
Patients who don't receive early treatment for ehrlichiosis run the risk of damaging their lungs, kidneys and brain. In rare cases, some patients have died from the disease.
Standard tick-borne disease tests don't detect the bacterium yet. Pritt, of the Mayo Clinic, said only a few labs, including hers, can identify it.
"We really want to get this message out to physicians so that they can think about it when they're examining patients," she said. "And also to patients, so they can think about it when they're presenting to their physicians and that the appropriate testing can be ordered."
Pritt doesn't know how the Ehrlichia bacteria established a foothold in Minnesota and Wisconsin. She said it's possible the new bacterium could have originated in Eastern Europe and Asia, and somehow hitched a ride to the United States.
But it's also possible that the new bacterium has been in the Midwest for a long time at very low levels, and only recently emerged as the tick population has surged.