Study finds Echinococcus multilocularis in Washington coyotes

A new University of Washington-led study suggests Echinococcus multilocularis is no longer just an inland or northern concern. In findings published March 24, 2026, in PLOS Neglected Tropical Diseases, researchers reported the parasite in 37% of 100 coyotes sampled in the Puget Sound region, the first confirmed detection in a wild host on the contiguous U.S. West Coast. (journals.plos.org)

That matters because E. multilocularis is the tapeworm behind alveolar echinococcosis, a rare but serious zoonotic disease. According to CDC and Washington State Department of Health materials, the parasite’s life cycle typically involves wild canids such as foxes and coyotes as definitive hosts and small rodents as intermediate hosts. Dogs can also serve as definitive hosts, shedding eggs in feces after exposure, while human disease may take years to appear and can behave like an invasive liver tumor. (cdc.gov)

The Washington study adds to a broader North American spread that researchers say has become more apparent over roughly the past 15 years. In UW’s summary of the work, lead author Yasmine Hentati said the prevalence in local coyotes was surprising, especially because the parasite had not been found in the Pacific Northwest until earlier in 2026. The same UW report says genetic analysis tied the coyotes’ infections to the more infectious European-origin variant now thought to predominate in the U.S. and Canada, rather than the older tundra variant previously reported from remote parts of Alaska. (washington.edu)

For clinicians, one of the most practical details is that the wildlife signal is strong even if companion animal disease remains uncommon. UW said there is still little evidence of broad spread into other hosts, but cited seven canine cases reported in Washington, Oregon, and Idaho since 2023, five of them in Washington. Separate surveillance published in 2024 found E. multilocularis DNA in 26 of more than 2.3 million dog fecal samples from the U.S. and Canada between March 2022 and July 2024, underscoring that confirmed canine detections are rare, but real. (washington.edu)

Industry and public health reaction has been measured rather than alarmist. UW researchers emphasized awareness and prevention, not panic. Hentati said, “The main takeaway is that Echinococcus multilocularis is here,” and that people should understand the potential risks. CDC prevention guidance aligns with that framing: limit dogs’ contact with rodents, wild canids, and feces, and reinforce hand hygiene after handling animals. Washington’s health department also maintains echinococcosis reporting and investigation guidance, reflecting the organism’s zoonotic relevance even though human disease remains rare. (washington.edu)

Why it matters: For veterinary teams in Washington and the broader Pacific Northwest, this is a surveillance story with exam-room implications. Practices may need a lower threshold to discuss parasite exposure in dogs that roam, hunt rodents, visit greenbelts, or have repeated wildlife contact. The finding also strengthens the case for region-specific client education: preventing predation and scavenging, considering risk-based parasite control, and recognizing that canine infection can be subclinical or, in alveolar disease, severe and difficult to manage. A 2023 JAVMA case series from the northwestern U.S. described naturally occurring alveolar echinococcosis in four dogs, highlighting the clinical consequences when infection progresses beyond intestinal carriage. (pubmed.ncbi.nlm.nih.gov)

What to watch: The next phase will likely center on expanded wildlife mapping, more targeted testing in domestic dogs, and whether state and local agencies update prevention messaging as more is learned about how widely the parasite is established in western Washington. If additional canine cases surface, veterinary awareness could become one of the most important early-warning tools. (journals.plos.org)