Dangerous tapeworm that can spread to dogs and humans confirmed in PNW coyotes for first time

A dangerous tapeworm, not found in Pacific Northwest wildlife until this year, is more widespread than researchers expected.

Echinococcus multilocularis, a tapeworm that can cause severe disease in humans and dogs, was detected in 37 out of 100 coyotes tested by the University of Washington (UW) in the Puget Sound region, according to a recent news release from UW.

Researchers said the tapeworm has been spreading across the United States and Canada, and lives as a parasite in coyotes, foxes, and other canid species. Yasmine Hentati, the lead author of the UW study, said a few people have contracted the tapeworm, and multiple dogs have gotten sick.

“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,” Hentati, who recently graduated from the UW with a doctorate in environmental and forest science, stated. “The fact that we found it here in one-third of our coyotes was surprising, because it wasn’t found anywhere in the Pacific Northwest until earlier this year.”

If left untreated, the tapeworm causes cancer-like cysts to form in the liver and sometimes other organs, according to the release. Without intervention, the tapeworm can lead to death. However, researchers noted not all carriers become ill. The host can support thousands of worms in their intestines without getting sick. The worms then shed eggs that are passed in their feces.

Tapeworm can spread to humans through food

Humans can pick up the parasite by eating tapeworm eggs in food contaminated with coyote or dog feces, and can develop a disease called alveolar echinococcosis, which leads to slow-growing metastatic cysts. Researchers noted symptoms may not appear for five to 15 years after exposure, making it harder to diagnose.

“Alveolar echinococcosis is considered the third most important food-borne illness globally, and one of the top 20 neglected tropical diseases by the World Health Organization. Many countries have developed robust protocols for tracking it,” the news release stated.

Dogs exposed to the parasite may or may not become sick, depending on the parasite’s life cycle. Researchers said it is more common for dogs to carry the parasite and not develop a disease, but dogs exposed to the parasite can develop the same cancer-like cysts as other infected animals.

How to protect your dog

Guilherme Verocai, the co-author of the study and an associate professor and director of the Parasitology Diagnostic Laboratory at the Texas A&M University College of Veterinary Medicine and Biomedical Sciences, said owners should not let their dogs prey on rodents or scavenge carcasses, as rodents can also pick up the tapeworm.

Verocai added that owners can give their dogs preventive medication for worms and ticks, and ensure routine veterinary care to test for parasites.

Although researchers found evidence of the tapeworm in local coyotes, they said there is little evidence of it spreading to other hosts.

“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 stated.

A different, more infectious variant

Before an uptick in the 2010s, there were several reports of the tapeworm on remote islands in Alaska, but those were caused by a parasite with different origins than the current outbreak, according to the news release.

Researchers pinned the earlier cases to a tundra variant, but said the recent outbreak is driven by a more infectious variant with European origins.

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