Risk of Lyme disease increases as warmer weather nears, experts say

With warmer weather approaching, environmental experts are reminding outdoor enthusiasts to protect themselves against Lyme disease.

Lyme borreliosis, more commonly known as Lyme disease, is caused by bacteria called Borrelia burgdorferi that lives on deer ticks. The ticks often travel on deer or mice through wooded areas. The disease can often cause a rash resembling a bull’s-eye and flu-like symptoms. If not treated with antibiotics, the disease can lead to severe joint pain or even paralysis of muscles in the face.

According to the Centers for Disease Control and Prevention, reported Lyme disease cases have doubled across the country since 2001 with most cases seen in the Upper Midwest and Northeast. Locally, researchers believe the disease isn’t necessarily spreading, but human exposure to the deer tick is growing.

“What we’re determining over time is that the ticks that carry the Lyme disease — the deer tick — is expanding geographically its range,” said Janet Jarnefeld, a tick specialist technician with Metropolitan Mosquito Control District, an organization monitoring tick-borne diseases in the Twin Cities since 1990.

Jarnefeld said researchers aren’t exactly sure what has caused an increase, but one possibility is a warming climate, which increases the amount of time ticks have to travel.

“We kind of have a new normal,” Jarnefeld said. “No one can really say exactly what the reasons would be for the increase in the number of ticks that are out and the spread that’s occurring, but one of the hypotheses is climate change.”

Fred Bonilla, an associate professor in the UW-River Falls Biology Department with a doctorate in infectious diseases and pathology, said climate change is a growing concern for those studying tick-borne diseases.

“The transmission of Lyme disease is mainly in the warmer months — our summer months — that’s when most of the transmission occurs,” Bonilla said. “The survivability of a tick is really important, so if it is surviving longer, we may start seeing an increase in cases in April or May as opposed to our typical June or July.”

Jarnefeld said deer ticks have already been seen this year, which is likely due to a stretch of warm weather in the middle of February.

About 1,300 confirmed cases of Lyme disease were reported across the state in 2015, according to the Wisconsin Division of Public Health. The highest numbers were recorded in June and July.

For people looking to explore the region’s woodland areas, Jarnefeld said there are easy steps people can take to prevent the transmission of the disease.

“Keep yourself along a center of a trail. Keeping yourself from shrubs brushing against you, you’re going to reduce the opportunity for ticks that are hanging out on the ends of the brush,” Jarnefeld said.

Jarnefeld also recommended people wear light-colored clothing and tuck their pants into their socks. Bonilla said people should be aware of the importance of protecting themselves from the disease.

“Like any disease, it has signs and symptoms that can have consequences,” Bonilla said. “In some cases, if it’s left untreated there could be some severe consequences.”

Jarnefeld said people must be aware of how early during the year ticks are coming out and how late in the year they can still be found. In 2015 and 2016, the MMCD reported finding ticks as early as March and as late as December.