New health risk from ticks is unique to Minnesota, WisconsinDoctors at the Mayo Clinic in Rochester, Minn., along with public health officials from both states are announcing the discovery Thursday in the New England Journal of Medicine in hopes of raising awareness among doctors and patients.
By: Christopher Snowbeck, St. Paul Pioneer Press / MCT
Researchers have discovered a new strain of bacteria that sickens humans by way of tick bites and apparently poses a health risk that's unique to Minnesota and Wisconsin.
Doctors at the Mayo Clinic in Rochester, Minn., along with public health officials from both states are announcing the discovery today in the New England Journal of Medicine in hopes of raising awareness among doctors and patients.
Since 2009, at least 25 people from Minnesota and Wisconsin have been sickened by the bug, which is a form of the bacteria called "ehrlichia." But public health experts said there's no need for panic.
"I don't think people should be scared," said Dave Neitzel, an expert in vector-borne diseases at the Minnesota Department of Health. "This is just the latest in a series of organisms being described, and I'd be surprised if it's the last."
Two other ehrlichia species are known to cause tick-borne illnesses primarily in the southern and south-central United States, and another strain of the bacteria exists in Europe and Asia. But the genetic fingerprint of the new bacterium -- first seen in 2009 at a hospital in Eau Claire -- has never before been documented, according to Mayo Clinic researchers.
It causes a feverish illness that usually can be treated with antibiotics, said Dr. Bobbi Pritt, a microbiologist at the Mayo Clinic. She said the bug likely is not as common as the Lyme disease bacterium that causes the most prevalent tick-borne ailment in the region.
"Protecting against ticks is very important," Pritt said.
Researchers started investigating in 2009 after technologist Carol Werner of the Mayo Clinic Health System's hospital in Eau Claire noted an abnormal finding on a test she was running. Doctors had ordered the test to see if a patient might be suffering from anaplasmosis -- a different tick-borne ailment that's becoming more common in the region -- and the test also happened to look for evidence of ehrlichia bugs.
On the graph of the test results, "there was a peak in an unusual, unexpected place," she said.
The next day, a co-worker in Eau Claire got the same result on a test for a different patient, Werner said. The samples and other information were sent to the Mayo Clinic in Rochester, which in turn contacted the U.S. Centers for Disease Control and Prevention in Atlanta.
Researchers at the University of Wisconsin-Madison and University of Minnesota got involved along with the state health departments. The Minnesota Department of Health in 2010 issued a health advisory about increased reports of ehrlichiosis -- the illness caused by the various ehrlichia species -- in humans.
To date, thousands of blood samples from across the United States have been screened by the Mayo Clinic, but Pritt said the bacterium has been found only in Wisconsin and Minnesota patients. Thousands of ticks across the country also have been studied, but, again, only ticks from the two Upper Midwest states have been carriers.
The bug also has been found in two mice -- one from Minnesota, the other from Wisconsin.
"As the deer tick population continues to spread and increase across Wisconsin, we are likely to see increasing incidence of this new infection, just as we have seen with Lyme disease and anaplsamosis, which are transmitted by the same tick species," said Susan Paskewitz, an entomologist at the University of Wisconsin-Madison, in a news release.
Deer ticks are the likely culprits in spreading the new infection, said Neitzel of the Minnesota Department of Health. The ticks also are known as "black-legged ticks" and are distinct from a common tick that's variously referred to as a "dog tick" or "wood tick."
The risk of tick-borne diseases in Minnesota is greatest from late spring through mid-summer, Neitzel said. The best way to prevent tick bites is to avoid the wooded or brushy areas that are home to deer ticks.
When going through tick country, people should use repellents, Neitzel said. Illnesses caused by the new bacterial strain have tended to be clustered in the central and east-central portions of the state that already are home to other tick-borne illnesses, Neitzel said.
"It's just another good reason to protect yourself from tick bites," Neitzel said.
There's been a lot of tick news already this year in Minnesota.
In May, the health department reported that the state saw a record number of tick-borne illnesses during 2010. In June, the state saw its first-ever death from a brain infection caused by Powassan virus -- a rare virus transmitted through the bite of an infected tick.
Also this summer, the local branch of the American Red Cross initiated a study to better understand how many blood donors have been infected with babesia, a parasite that can be spread by ticks but also through blood transfusions.
Still, it's hard to say if the recent developments stem from a fundamental change in the tick population or simply reflect the fact that scientists have better tools for discovering problems.
"The truth is probably a combination of both," Neitzel said. "We have better diagnostic tools, but we're also seeing ticks and infected ticks in places where they haven't been seen before."
So far, the new bacterial strain has not caused any deadly infections. As with some other tick-borne ailments, the danger from the new bug could be most pronounced in people with compromised immune systems, where some infections might ultimately prove deadly, said Pritt, the microbiologist at the Mayo Clinic.
The public health messages surrounding the new bug sound similar to those with other tick-borne illnesses. But for scientists, the discovery raises intriguing new questions.
For example: The new bacterium appears to be closely related to the ehrlichia strain that's found in Europe and Asia, Pritt said. Could that have been the origin for the new species and, if so, how did it get here?
"We don't have a definitive answer," Pritt said. "Was it in Canada and is it now just coming to our two states? Has it been here for ages? Or, was it recently introduced? We just don't know."
WHAT TO LOOK FOR
Symptoms of the ehrlichia bacteria include fever, muscle pain and headache. Severe disease could produce gastrointestinal, kidney, respiratory and central nervous system problems and, in rare cases, death.
If you can't avoid tick habitat, consider these suggestions from the Minnesota Department of Health:
- Use repellents that are up to 30 percent DEET and apply them to clothing or skin for temporary protection.
- Use permethrin-based repellents on clothes. The repellents are used to pretreat fabric and can protect against tick bites for at least two weeks.
- Yards are less attractive to ticks when lawns are mowed short, leaves and brush are removed and a barrier of wood chips or rocks separates lawns from woods.
Distributed by McClatchy-Tribune Information Services.