Ticks spreading in the Pacific Northwest? Warming trends could worsen health threat

Blood suckers are on the move in the Pacific Northwest, and their bites can be dangerous.

More commonly found in the Midwest and northeast, ticks are expanding their range. And Washington state is not immune.

Warming trends, exacerbated by climate change, are creating a more hospitable environment for the parasites.

The first case of a locally transmitted tick-borne illness popped up last year in a Whatcom County man. Then last month, doctors found the state’s second case after a Puyallup woman fell ill.

Now, public health officials are warning that more cases of the potentially fatal bacterial disease, called anaplasmosis, and other tick-borne pathogens, are on the horizon. Not only are warmer conditions more suitable for ticks but people are also moving to more areas where the parasites thrive.

More exposure to ticks means more bites and, in turn, more disease. Already some illnesses, like Lyme disease, are on the rise in places where the parasites are more common. And malaria is popping up in southern states.

“This is not going away,” said Dana Shaw, an assistant professor at Washington State University’s College of Veterinary Medicine.

Farther east, tick populations are reaching deeper into Canadian territory than they have in past decades. One study, published early last year in the scientific journal Pathogens, indicates that ticks in northern California are also expanding their range and highlights the potential for the parasite populations in Oregon and Washington.

While scientists don’t understand precisely how much tick populations have grown in Washington, their shift in habitat is part of a warming climate, said Katharine Walter, an assistant professor of epidemiology at the University of Utah. People don’t necessarily need to be afraid of the new landscape but they should pay attention, she said.

“The climate crisis comes with all sorts of health risks,” Walter said. “It’s here now, not in some distant future.”

Shifting habitat

While anaplasmosis is relatively uncommon for Washington, it’s not new. The disease is far more common in the northeast and the Midwest, where it’s spread by the blacklegged tick (Ixodes scapularis).

In the West, the disease is spread by the western blacklegged tick (Ixodes pacificus) and is most common in northern California, said Monika Gulia-Nuss, an assistant professor of biochemistry and molecular biology at the University of Nevada, Reno.

But warming trends — globally and regionally — mean their suitable range is extending farther north, said Gulia-Nuss, who co-authored the 2022 study focused on northern California.

Changing climate patterns also mean deer and other mammals that carry ticks are venturing into new areas, Walter said. And people are increasingly developing new lands, encroaching into tick territory.

Most tick species in Washington are active between November and May, said Liz Dykstra, public health entomologist for the state Department of Health. Generally they’re most active around mid-April.

Precisely how climate change will alter those active periods is not yet clear and much will depend on the region, Dykstra said. More research is needed.

Perhaps ticks could start to climb into higher altitudes, Dykstra said. Or new species could make their way into the Pacific Northwest.

The lone star tick is one that doesn’t currently live in Washington but could be introduced here, Dykstra said. That species has already expanded north and east in recent decades. If an “engorged” female arrived in Washington and laid eggs, it could establish a population in the region “and it would be happy,” she said.

“That’s also what we call a hunter,” Dykstra said. “Where it’s not necessarily content to sit on a blade of grass and wait for you.”

The first two cases

Across the country, anaplasmosis is the second most common disease spread by ticks, Shaw said. But until last year a locally transmitted case hadn’t been documented in humans in Washington.

Symptoms of anaplasmosis include lethargy, fever, head and muscle aches and nausea. It can be fatal if left untreated, though treatment comes from a relatively common antibiotic.

Washington doctors diagnosed the first local human case last August after an infected tick likely bit a Whatcom County man in his 80s, who was hospitalized and then released.

Then, last month doctors diagnosed a Puyallup woman in her 40s with the disease, according to a Tacoma-Pierce County Health Department news release. She was likely bitten by an infected tick in the brushy area around Puyallup or Eatonville.

The unidentified woman was hospitalized for 10 days, said a department spokesman. By mid-July, she had been released and was recovering at home. Local health officials are monitoring for additional cases and state officials are examining ticks in the areas the woman had visited.

“The climate crisis is, of course, a health crisis.”

Cases of anaplasmosis do pop up in Washington, said Hanna Oltean, head of the state Department of Health’s Zoonotic and Vector-borne Disease Program. But until recently they’ve stemmed from people who traveled to the northeast or Midwest and returned to the Pacific Northwest before they began to exhibit symptoms.

The case in June and the other last August are unique because they’re the first two documented cases in Washington where the people infected hadn’t traveled and were instead bitten by an infected tick in-state, Oltean said.

Those two cases are almost certainly not the first two human cases of locally contracted anaplasmosis, though, Gulia-Nuss said. They’re just the first to be documented.

Each year, dogs throughout the Pacific Northwest contract the disease, indicating that ticks carrying the pathogen do live throughout the region, Shaw said.

Dogs in Washington are currently at high risk to contract anaplasmosis if they’re bit by a tick, according to Pet Disease Alerts, an Oregon-based nonprofit tracking these types of diseases. In August, Chelan, Clallam, Douglas, Franklin, Island, Jefferson, Kitsap, Klickitat, Mason and Yakima counties show the highest risk.

Statewide, the nonprofit indicates a nearly 2% infection rate for dogs bitten by ticks.

Infections among dogs also likely indicates that people have been contracting the disease as well, but their cases go undiagnosed and undocumented, Gulia-Nuss said. Perhaps those people didn’t fall ill enough to seek medical attention or, if they did, their doctors didn’t know to look for anaplasmosis.

“If you don’t look, you don’t find,” Gulia-Nuss said.

As the ticks expand their range, more severe cases will become increasingly common, Walter said.

People who work or live outside will often be at higher risk, Walter said. Marginalized people, those who have little or no access to health care, will suffer the most. This is true not just for anaplasmosis but also for other diseases popping up in greater numbers.

Cases of Lyme disease, the most common tick-borne disease, nearly doubled between 1991 and 2018, according to the U.S. Environmental Protection Agency. And a report published Thursday by the U.S. Centers for Disease Control and Prevention shows that since 2010 more than 110,000 people have contracted alpha-gal syndrome, a potentially fatal condition, through which the infected develop an allergy to red meat.

The phenomenon isn’t limited to tick-borne diseases either. This summer, seven people in Florida and one in Texas contracted malaria, the first resurgence of the mosquito-spread disease in decades.

The trends are only likely to continue, Walter said. “The climate crisis is, of course, a health crisis.”

Getting used to it

Since little can be done about the tick’s expanded range and active seasons, people must adjust, Shaw said.

“This is something that people are just going to have to get used to and get used to being vigilant against,” she said.

Remember too that not all tick bites result in an infection, Dykstra said, but it’s best to minimize your risk whenever possible.

Tick habitats are often found in wooded and brushy areas, particularly those with tall grass and fallen leaves, Dykstra said. Pants (tucked into your socks) and long-sleeved shirts can keep the ticks at bay. And light-colored clothing can help you spot them.

Tick repellent works as well. You can apply to your skin and clothing.

When you’re out of the tick habitat, remember to check yourself and your pets, Dykstra said. Shower, if possible.

If you’ve been bitten, use clean, fine-tipped tweezers to grasp the tick as close to the skin as possible and pull directly up with steady pressure. If the tick’s mouthparts break off in your skin you can try to remove them with tweezers, otherwise keep clean and let your skin heal.

There might be a red bump on the bite area for several weeks after, Dykstra said.

“That doesn’t mean you’ve been infected with a pathogen,” she said. “That’s your body cleaning it out.”

But if you begin to feel sick, see a health care provider and let them know you were recently bitten by a tick.

You can also save the tick you’ve removed in a container and send it to the Department of Health for identification. Additional information can be found at doh.wa.gov.