Warmer winters allow ticks to survive and bite year-round

While most insects die in winter, ticks are relatively immune to frigid temperatures and, as the planet warms from the climate crisis, they are becoming increasingly active in the cold months, experts warn.

These tiny, pestiferous bloodsuckers hide out on cold days and wait for temperatures to rise before coming out and waiting for an opportunity to pounce on you or your beloved pets.

Winters used to always be colder, explains Rafal Tokarz, an epidemiologist at the Center for Infection and Immunity at Columbia University Mailman School of Public Health.

“Now we have periods of abnormally warm weather and (ticks) appear more frequently,” he adds.

Furthermore, as the winter days are more pleasant, people go out for a walk with their dogs or their family. “The ticks will be there,” said Tokarz, who also warns that the increase in bites “contributes to a higher number of Lyme cases in the winter.”

A deer tick under a microscope. Victoria Arocho / AP

Emergency room visits for tick bites, which were declining from a peak in the summer, are increasing in some parts of the United States, especially in the Northeast, according to the Centers for Disease Control and Prevention.

Climate change helps ticks

While tick bites are expected to drop as sub-zero temperatures arrive, the climate emergency is making matters worse.

The federal government released its new National Climate Assessment report on Tuesday, predicting that most areas of the United States will experience temperature increases.

“So the risk of a tick finding us in winter will be greater,” said Richard Ostfeld, an expert on these insects at the Cary Institute for Ecosystem Studies in Millbrook, New York.

Leg of a man with Lyme disease
Leg of a man with Lyme diseaseGetty Images

Ticks that transmit Lyme disease can be active all winter, he said. “When the heat returns, in March and April, we will see a second wave of activity” among those who have not yet found someone to bite, the expert added.

This also applies to other species of concern in the United States, such as lone star ticks and dog ticks, Ostfeld said, which can both infect people with Rocky Mountain fever.

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So people should worry all year about Lyme disease, which is transmitted by the bite of a black-legged tick, experts warn. Lyme disease is the most common tick-borne disease in the United States, with between 30,000 and 500,000 cases each year.

Rising temperatures due to the climate crisis have also caused ticks to spread to new geographic areas.

When winter comes and temperatures drop, ticks that began appearing in the fall “make themselves comfortable under the leaf litter,” said Laura Goodman, an infectious disease researcher at Cornell University.

“Depending on how well insulated they are, they can hold up perfectly well,” he said, and “as soon as it gets warmer or a little sunny they will come back.”

People should also be aware that even when the temperature is low, there may be places where it feels warmer, Goodman said. “Thinking about the general (weather) forecast does not help much in this situation,” they warn.

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Ticks are much more resistant than you might think: “We put them in the freezer in the laboratory and then we took them out and they were still alive. You have to freeze and dry them so they die,” she explains.

Infected by mice or deer

Ticks have a three-stage life cycle, and in each stage they only take a “blood ration,” Tokarz said.

The first stage, the larva, is not of concern because the ticks have not contracted the bacteria that causes Lyme disease, officially known as Borrelia burgdorferi. The larvae become infected when they bite a mouse infected with the bacteria.

When they become nymphs, their next stage, infected ticks can transmit the disease to humans, their pets and other animals, which can also carry the bacteria.

By the time ticks become adults they have had two opportunities to contract Borrelia burgdorferi: from infected mice in their larval stage and from infected animals, often deer, in their nymph stage.

Ticks in the nymph stage can be difficult to detect because they are the size of a poppy seed, experts say. Adults are much larger and easier to spot.

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Studies with Topaz ticks on Long Island, New York, revealed that 15% to 20% of nymphs carried the bacteria, compared to 60% to 75% of adults.

The bad news then is that, if someone is bitten by an adult tick in winter, there is a much greater chance of becoming infected and transmitting the bacteria than a nymph in spring or early summer.

The good news is that because adult ticks are much larger, they are easier to detect and remove before they transmit the bacteria that causes the disease.

“As long as the tick is removed quickly, the chances of infection are dramatically reduced,” explains Tokarz.

While most Lyme cases are reported in the spring and summer, there are reports every month, he adds.

How to avoid bites in colder climates

Experts suggest several steps people can take to avoid contracting Lyme in the winter months:

  • When you return from a walk, or any other place where you may have picked up a tick, check carefully.
  • Use insect repellent.
  • Wear lighter clothing if you are hiking so ticks can be easily spotted.
  • If there’s any chance you may have picked up a tick, throw your clothes in the dryer rather than the washing machine because the dry heat will kill them.

If you find a tick attached to your skin but don’t develop a rash, don’t assume you don’t have Lyme. Testing can be complicated, but health authorities recommend using a combination of antibody tests, including an antibody immunoassay test such as ELISA, followed by an antibody immunoblot test such as Western blot testing.

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As for pets, there are also measures to protect them, including a Lyme vaccine for dogs; and liquids for cats and dogs that can be put on the animal’s neck or pills to protect them. Also check your pets regularly, throughout the year, for ticks.

“You can never let your guard down completely,” Goodman says.