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A Tapeworm That Can Kill Your Dog Is Now in Washington Coyotes. Here's What You Need to Know.
By Billy Olesen, Owner and ACE | Pest Stop Services, Inc.
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I want to be upfront about something before you read this: we don't treat for tapeworms. This isn't a sales pitch. I'm writing this because a new study came out of the University of Washington that every dog owner in Western Washington should know about, and I'm not sure enough people have seen it.
We're a pest control company, but we're also animal people. I keep honeybee hives on my property. My team cares about the environment we work in every day. And when researchers publish findings this close to home about a parasite that can seriously harm or kill dogs, and in rare cases people, sharing it is just the right thing to do.
So here's what the UW found, what it means for your dog, and what you can actually do about it.
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What the Study Found
In March 2026, researchers from the University of Washington published a study in PLOS Neglected Tropical Diseases that should get the attention of anyone who owns a dog in the Puget Sound region.
The study detected a parasitic tapeworm called *Echinococcus multilocularis* in the intestines of one-third of coyotes surveyed in Washington. Specifically, researchers surveyed 100 coyotes in the Puget Sound region and found the parasite in 37 of them.
That's a 37% prevalence rate. In our backyard.
This is the first time *E. multilocularis* has been detected in a wild host on the West Coast of the contiguous U.S. It's not a theoretical future threat. It's already here, already common in local wildlife, and the researchers were surprised by how widespread it is.
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Why This Parasite Is Serious
*Echinococcus multilocularis* isn't your garden-variety intestinal worm. When it infects an animal or person, it causes cancer-like cysts to form in the liver and sometimes other organs. If untreated, infection can be fatal.
The disease it causes in humans is called alveolar echinococcosis, and one of the scariest things about it is the timeline. Symptoms may not appear for five to 15 years after exposure, which complicates diagnosis and treatment. The World Health Organization classifies it as one of the top 20 neglected tropical diseases globally.
For dogs, the picture is a little different. Domestic dogs that are exposed to *E. multilocularis* may or may not become sick, depending on where the parasite is in its life cycle at exposure. It is more common for dogs to carry the parasite and shed eggs without developing disease, but dogs that are exposed to parasite eggs may develop the same cancer-like cysts.
"This parasite is concerning because it has been spreading across North America. There have been numerous cases of dogs getting sick, and a handful of people have also picked up the tapeworm," said lead researcher Yasmine Hentati.
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How the Life Cycle Works
Understanding how this parasite spreads helps you understand how to protect your dog.
Coyotes are the primary host. They can support thousands of worms in their intestines without becoming sick, and the worms shed eggs that are passed in their feces.
Rodents then pick up those eggs by eating food contaminated with coyote feces. Once consumed, the parasite eggs migrate to the liver and form cysts, ultimately weakening or killing the rodents. The parasite's life cycle begins again when coyotes prey upon infected rodents.
Dogs and people are what researchers call accidental hosts. Humans may pick up the parasite by consuming tapeworm eggs in food contaminated with coyote or dog feces. Dogs are most at risk when they hunt or scavenge rodents.
"The reason that it's so high in coyotes is because they are regularly eating raw rodents, and that is the primary way for them to get infected. Most domestic dogs are not eating the raw livers of wild rodents," Hentati said.
That's actually reassuring context. The risk to your average house dog is real but not inevitable. It depends heavily on your dog's behavior and habits.
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What You Can Do Right Now
The researchers and veterinary experts on this study were clear about practical steps pet owners can take.
- Don't let your dog hunt or scavenge rodents.** This is the primary transmission pathway. Co-author Guilherme Verocai, director of the Parasitology Diagnostic Laboratory at Texas A&M's College of Veterinary Medicine, said owners should not let dogs prey on rodents or scavenge their carcasses.
- Keep up with routine deworming and vet visits.** Owners can give dogs preventative medication for worms and ensure routine veterinary care, which should include diagnostic tests for parasites. Talk to your vet specifically about *E. multilocularis* if you have a dog that spends a lot of time outdoors or in areas with heavy wildlife activity.
- Be mindful in coyote territory.** Coyotes are everywhere in Western Washington, including urban parks, greenbelts, and suburban neighborhoods. If your dog is off-leash in areas where coyotes are active, that's where the risk concentrates.
- Wash your hands and your produce.** The human transmission pathway runs through fecal contamination of food. Basic hygiene and washing garden produce are practical steps, especially if you live in an area with wildlife activity.
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Why This Is a Bigger Deal Than It Might Seem
*E. multilocularis* was considered extremely rare in North America until approximately 15 years ago, when cases in humans and dogs began cropping up in Canada and the midwestern U.S. The current outbreak is being driven by a European variant that appears to be more infectious than the strain historically found in Alaska.
Neither Canada nor the U.S. require dogs to undergo deworming upon arrival, which may explain the spread. Without systematic surveillance or entry requirements, this parasite has quietly moved west and is now established in our region.
Only seven cases of the parasite in dogs have been reported in Washington, Oregon, and Idaho since 2023, and few human cases have been reported in the U.S. overall. So the risk remains low in absolute terms. But the presence of the parasite in more than a third of local coyotes means the environmental exposure is real and growing.
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A Note from Us
Again, we don't treat for tapeworms. Your veterinarian is the right call here, and I'd encourage anyone with outdoor dogs to bring this study up at your next appointment.
We shared this because we believe an informed community is a healthier one, and because the wildlife we share this region with, including the coyotes, the rodents, and every other species in the ecosystem, are part of the environment we all live in together.
If you have questions about pest pressures around your home that might be attracting wildlife, we're happy to talk. But for this one, call your vet.
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**Source:** Hentati, Y. et al. (2026). Detection of *Echinococcus multilocularis* in coyotes in Washington State, USA highlights need for increased wildlife surveillance. *PLOS Neglected Tropical Diseases.* Published March 24, 2026.
Full UW News release: [washington.edu/news](https://www.washington.edu/news/2026/04/06/parasitic-tapeworm-a-risk-to-domestic-dogs-and-humans-found-in-washington-coyotes/)
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*Pest Stop Services, Inc. is a family-owned pest management company based in Tumwater, Washington, serving Western Washington and Oregon since 1988. Billy Olesen holds the Associate Certified Entomologist (ACE) credential and serves as a Commissioner on the Washington Commission on Integrated Pest Management.*