Ticks bearing Lyme disease rampant in Wisconsin
Wisconsin deer hunters will soon head to the woods, and a growing number of ticks carrying disease-causing bacteria will be there, too.
Wisconsin has long been a hotspot for Lyme disease. But evidence is mounting of just how many deer ticks in the state carry the bacterium that causes the disease, and how many more Wisconsinites than previously thought are contracting Lyme disease.
A new study at the University of Wisconsin-Eau Claire found that an average 35% of 341 adult female deer ticks collected from 21 counties scattered around Wisconsin from 2010 to 2013 tested positive for the Lyme bacterium.
"We are seeing increases in cases because the population of ticks is expanding," said Diep (Zip) Hoang Johnson, a vector-borne epidemiologist in the division of public health at the state Department of Health Services.
The increase could be the result of climate change, she said, but humans also are moving into tick territory to build homes. "Now, they're living right in our backyard," Johnson said.
Lyme disease typically causes flu-like symptoms and, in about 70% of cases, a telltale bull's eye rash at the site of the bite. If not treated promptly with the right antibiotics, the disease can lead to arthritis, meningitis, heart problems and other serious complications.
Only blacklegged ticks, commonly called deer ticks, carry the Lyme disease-causing bacterium Borrelia burgdorferi, according to the Centers for Disease Control and Prevention. The ticks also are responsible for other, lesser-known diseases.
Experts in recent years have begun mapping high-risk areas where the most ticks carrying the Lyme bacterium have been found. Previously, high-risk areas were mapped by reported cases of Lyme disease. But officials now realize those numbers are unreliable and don't reflect the true extent of the risk.
In fact, the CDC in August reported that the total number of people diagnosed with Lyme disease is roughly 10 times higher than the yearly number of cases reported to the CDC. So while 30,000 new Lyme disease cases are reported nationwide each year, the actual number is around 300,000.
Under-reporting is more likely to occur in places with high concentrations of disease-carrying ticks, such as Wisconsin, according to the CDC.
In the UW-Eau Claire study, the Wisconsin counties with the highest infected tick prevalence rates were Chippewa (66.7%); Dunn (44.4%); and Eau Claire (36.5%).
The prevalence also significantly increased each year of the research by Lloyd Turtinen, a virologist and biology professor, and several undergrads who collected the ticks and did much of the testing.
In 2010, the infected tick prevalence from all 21 counties was 21.6%. It increased to 32.4% in 2011, 40.9% in 2012, and 51.2% in 2013, according to Turtinen.
"It reinforces what we know," said Susan Paskewitz, a UW-Madison professor of entomology and the state's leading expert on ticks and their transmission of Lyme disease.
Not every physician reports Lyme disease cases, even though reporting is required, because not all persons with Lyme disease get the bull's eye rash that automatically makes it reportable. Lyme disease also is often misdiagnosed because many of its symptoms are similar to other infections, rheumatoid arthritis and various neurological diseases, Johnson said.
Blood tests for the disease are tricky because the body may not produce an antibody to the bacterium for weeks after a tick bite. If a patient doesn't get tested at the right time, and doesn't meet both the lab and clinical criteria for Lyme disease, the case isn't counted in the official state total.
This time of year, public health experts are especially concerned about deer hunters, who tend not to spray DEET repellent on their clothing before going into the woods because the scent can warn deer of their presence. A less noticeable tick repellent containing permethrin is recommended.
Hunters and others who go out in the woods or tall grass any time of the year should do immediate tick checks afterward, and take a shower to rinse off any ticks that may be crawling on them, looking for a spot to attach.
An infected tick must remain attached to the skin for more than 24 hours to transmit the Lyme bacterium, according to experts. A tick check should include the scalp, behind the ears, and body folds such as armpits and behind the knees where ticks tend to attach.
To remove a tick, grasp its mouth part as close to the skin as possible with a pointed tweezers, and steadily pull upward without twisting. Check pets, too. One prophylaxis dose of antibiotic may be prescribed by a physician within 72 hours after tick removal to prevent illness.
Staying on mowed trails at parks can reduce the chances of encountering ticks.
Unlike mosquitoes, ticks don't die when it gets cold. They live for up to two years and go dormant when temperatures fall below 40 degrees. They can awaken and begin feeding again when they're picked up by a person or dog, and brought in from the cold.
Immature ticks do most of the bacteria transmitting to humans because they're hard to see — about the size of a poppy seed — and it's much more likely that adult ticks will be pulled off within 24 hours of attaching to the skin.
Lyme disease was first identified in 1976 in a cluster of children in Lyme, Conn., who experts initially thought had rheumatoid arthritis. The disease has been reported in all states, but the vast majority of cases have been across much of the Northeast, from Maine to northern Virginia, and the upper Midwest.