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05/14/2025 | News release | Distributed by Public on 05/15/2025 01:55

Tick-Borne Diseases Risk Increasing Due to Climate Change: What You Need to Know

Tick-Borne Diseases Risk Increasing Due to Climate Change: What You Need to Know

BU infectious disease experts offer tips on how to protect yoursel

Nobody wants to see this: a deer tick on human skin. BU infectious disease experts say the risk from tick-borne diseases is increasing. Photo by Ladislav Kubeš/iStock

Infectious Diseases

Tick-Borne Diseases Risk Increasing Due to Climate Change: What You Need to Know

BU infectious disease experts offer tips on how to protect yourself

May 14, 2025
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It's spring, the season that marks the return of flowers, shorts and T-shirts, picnics-and ticks. And the bad news is that the threat from tick-borne diseases that can be serious and sometimes deadly is on the rise.

A warming climate has brought higher populations and a wider range for deer ticks in New England, as well as a longer tick season. Ticks that latch onto human beings for a blood meal can also infect them with Lyme disease, Anaplasmosis, Babesiosis, and Powasson virus. Lyme is endemic and well known; the other three are relatively rare, but the number of cases is growing steadily, including in Boston, according to Boston University infectious disease experts.

"We have seen more incursion of ticks into urban landscapes," says Cassandra Pierre, an assistant professor of infectious diseases at the Chobanian & Avedisian School of Medicine, and Boston Medical Center's medical director of public health programs and associate hospital epidemiologist.

"Unfortunately, I've seen people who are tenuously housed, just in the city on a bench, and they have not just Lyme, but Babesiosis," Pierre says. "I think that this calls for changing our perception of what the exposure range is, even for us. It's likely that if you go to the Stony Brook Preserve [in Hyde Park], you're going to have to do a more thorough tick check afterwards for sure. But if you're just on the Boston Common, unfortunately ticks have expanded into this area too."

The growth of the tick-disease threat to people and animals has expanded widely across the United States and into Canada, as well as in Europe, she says. Different types of ticks or ticks in different areas may carry different diseases, such as Rocky Mountain Spotted Fever, which is common in the central and southern United States.

But the correlation with a warming climate is clear, says Daniel Bourque, a Chobanian & Avedisian School of Medicine assistant professor of infectious diseases. "The Ixodes scapularis [deer tick] range is increasing. Its numbers are increasing. And with that, you're seeing an increasing incidence of these diseases.

"To take Powassan as an example," Bourque says, "it's still relatively uncommon, but it's something that we have seen increasing cases of pretty much every year. Think of it as similar to Eastern equine encephalitis, or triple E, a mosquito-borne disease that's uncommon, but when it does occur there's a lot of very severe illness with high risk of mortality."

Bourque does say that some of the increase in reported cases is likely due to increased disease recognition, as doctors more readily consider and test for Powassan when a patient presents with encephalitis symptoms, whereas a decade or more ago that was unlikely.

He says Babesiosis may be seeing the largest increase among the tick-borne diseases, as it expands away from southern and coastal regions.

"As clinicians, we used to anticipate the start of Lyme season as inevitable as allergy season, but the seasonality is absolutely changing," Pierre says. "We have warmer winters and earlier springs and there's humidity that comes with that in this area. Ticks love warmer, wetter climates. And not only do they love that, but their hosts tend to as well. The deer, the mice-when their ranges and numbers increase, we absolutely are going to see an expansion of ticks. And longer warmer weather also allows for there to be more exposure to ticks, because people are out more."

Sustained cold spells reduce the tick population, but we've had fewer of those, Bourque notes. "Once it warms up for even a couple of days, ticks become active. And that could happen really at any time of the year now," he says. "Lyme transmission can occur really in any month."

Ticks bite humans and other mammals for a blood meal (not with intent to transmit a disease). They generally have to attach to a human for at least 30 hours to transmit Lyme, but require a shorter time for the other diseases.

While there is talk about a Lyme vaccine coming down the pike, it's not here yet. So what can we do to stay safe? Pierre and Bourque strongly encourage a short list of precautions for those going into grassy or wooded areas:

Wear protective clothing, including light-colored clothing that covers the skin. That means long sleeves, socks, and long pants. "I know that list is not very sexy for summer, not beloved in a summer wardrobe, but I'm into harm reduction when it comes to any kind of infectious disease," Pierre says.

Use two kinds of insect repellent, DEET or picaridin for the skin, and permethrin on clothing. Both are usually effective in preventing bites from ticks (and mosquitoes). Treating clothing with permethrin is effective for several weeks or several washes.

Regular tick checks of people and pets. "My children, I find tons of ticks on them all summer," Bourque says. "Ticks can be hard to find, so another thing you can do to reduce tick attachment-if we're going for a hike, I might have them take a shower after the hike. If you take a hot shower before the ticks attach, you'll just wash them off your body." Ticks may also be on your clothing initially and then migrate to the skin. So after a walk, throw your clothes into the dryer on high heat for 20 minutes, and it will kill any ticks that are on your clothing.

If you see a rash or an attached tick, call your doctor. "That's a big one that a lot of people still don't know about," Pierre says. "You can get the antibiotics, one dose that will reduce your chance of being infected [with Lyme]." A lot of people don't see a tick at all, she says, only the rash signalling a bite or infection. And not just the classic bullseye rash from Lyme, but any rash that's not itchy or painful or could be explained by another cause. "You're just seeing a red rash on your skin and you can't explain it? Call your doctor."

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  • Joel Brown

    Senior Staff Writer

    Joel Brown is a senior staff writer at BU Today and Creatives editor of Bostonia magazine. He wrote more than 700 stories for the Boston Globe and has also worked as an editor and reporter for the Boston Herald and the Greenfield Recorder. Profile

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