AINEWS
First West Coast detection: Echinococcus multilocularis found in one-third of Puget Sound coyotes
The University of Washington study that confirmed the parasite also shows why standard fecal only surveillance has been missing it for years.
The University of Washington study that confirmed the parasite also shows why standard fecal only surveillance has been missing it for years.
When University of Washington researcher Yasmine Hentati and her colleagues tested coyote carcasses collected around Puget Sound, they recovered something the region's routine wildlife surveillance had been missing: Echinococcus multilocularis, a small tapeworm whose European lineage has now reached the contiguous U.S. West Coast for the first time in a wild host. The finding, published in PLOS Neglected Tropical Diseases, was a deliberate follow-up to a detection problem the team had already identified (Hentati et al., PLOS NTDs, 2026).
Thirty-seven of 100 coyotes sampled in the study carried the parasite, a prevalence of 37 percent when morphological identification and next-generation sequencing were combined (ScienceDaily summary of the UW release). None of the field-collected scats from the same areas came back positive, even though carcasses from those same regions did. The mismatch is the diagnostic story, not a footnote: non-invasive fecal DNA metabarcoding, the method most wildlife agencies use to track this parasite, systematically undercounts it.
The haplotype the team recovered tells a second story. The Washington samples matched an isolate first published from a dog in Quesnel, British Columbia, and sit two base pairs away from the French mtG h1 reference haplotype. That genetic signature supports a European-origin introduction into the Pacific Northwest, not a westward spread from the older North American midwest lineage that has been documented in coyotes and foxes in states including Indiana, Ohio, Illinois, Michigan, Nebraska, Kansas, and Wyoming since the 1990s (background on prior U.S. detections summarized in the same release).
The human stakes are real but specific. E. multilocularis causes alveolar echinococcosis, a cancer-like liver infection with a five-to-fifteen-year latency that is frequently fatal without aggressive treatment. The World Health Organization lists the disease among its top 20 neglected tropical diseases and ranks it as the third most important food-borne parasitic illness globally. Human cases in North America remain rare and are tied to specific exposures: wild canid scat, and dogs that ingest infected rodents or scavenge wild canid feces. No human West Coast cases have been reported as of June 11, 2026.
Co-author Guilherme Verocai, who directs the Parasitology Diagnostic Laboratory at Texas A&M's College of Veterinary Medicine, has pointed regional dog owners toward a small set of concrete steps: keep dogs from preying on rodents or scavenging rodent carcasses, maintain routine veterinary care, and discuss parasite screening with a vet in areas where the parasite has been confirmed (Verocai's guidance, as reported by UW and ScienceDaily). Seven canine E. multilocularis cases have been documented in Washington, Oregon, and Idaho since 2023; five of those were in Washington.
The detection is also a planning signal for state wildlife and public health agencies. Fecal-only surveillance missed this parasite in the very counties where it was later confirmed in carcasses, which means current maps of where E. multilocularis is and is not in the Pacific Northwest are likely too thin to support confident "absent" calls. Funding for the work came from the U.S. National Science Foundation and the UW Hall Conservation Genetics Fund (paper details in PubMed). The constructive question is no longer whether the parasite is on the West Coast, but whether regional surveillance, veterinary screening, and dog-owner guidance can keep pace with a parasite that has spent roughly fifteen years quietly crossing the continent.