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Coyotes Provided the First Wild-Host Detection of Echinococcus multilocularis on the U.S. West Coast

Coyote standing in vegetation in western Washington
Research · Disease, parasites & microbiology

Free-ranging coyotes (Canis latrans) in Washington, USA State have provided the first confirmation of Echinococcus multilocularis in a wild host on the west coast of the contiguous United States. The study, published on 24 March 2026 in PLOS Neglected Tropical Diseases, detected the zoonotic tapeworm in 37 of the 100 coyotes represented in the combined dataset.

Echinococcus multilocularis uses canids as definitive hosts, where the adult tapeworm lives and reproduces, while rodents normally act as intermediate hosts. Humans can become accidental intermediate hosts and develop alveolar echinococcosis, a severe disease caused by the parasite’s larval stage.

The researchers examined coyote carcasses and field-collected scats from a densely populated part of Washington. Adult tapeworms found in intestinal samples were first identified by their morphology and then confirmed with next-generation DNA sequencing. The team also used molecular methods to test fecal material for parasite DNA.

Map of coyote sampling locations and Echinococcus multilocularis infection status in western Washington
Coyote carcass and scat sampling locations and infection status in western Washington. Figure 3 from Hentati et al. (2026), PLOS Neglected Tropical Diseases, CC BY 4.0.

37 of 100 coyotes were positive

Combining the different approaches, 37 of the 100 coyotes represented across all sample types were positive for E. multilocularis. The authors describe the finding as evidence that the parasite is established and widespread in the sampled area, rather than an isolated detection in a single animal.

Sequencing also revealed a parasite haplotype — a genetic variant defined by a particular combination of DNA sequence differences — matching one previously documented in British Columbia, Canada, and regarded as being of European origin. The genetic match adds information that can be used to follow the geographic expansion of the parasite in western North America.

Representative Echinococcus multilocularis specimens used for morphological identification
Representative Echinococcus multilocularis specimens used for morphological identification. Figure 5 from Hentati et al. (2026), PLOS Neglected Tropical Diseases, CC BY 4.0.

Fecal DNA alone may underestimate occurrence

The study found that parasite DNA was detected less reliably in fecal samples than in intestinal material. One-third of infections were detected with intestinal swabs and/or morphological identification but not with fecal samples, and none of the 30 field-collected scats tested positive. The authors therefore warn that non-invasive surveillance based only on fecal DNA metabarcoding — sequencing DNA from mixed samples to identify the organisms present — may underestimate how commonly the parasite occurs. As part of the work, they also developed a new next-generation sequencing primer, a short DNA sequence designed to target cestodes in canid samples.

Because coyotes are common in Washington and frequently occupy landscapes shared with people and domestic dogs, the researchers argue that wild-canid surveillance can provide an early indication of changes in the parasite’s distribution. Their results extend the confirmed wild-host range of E. multilocularis to the U.S. Pacific coast and highlight coyotes as an important species for tracking its continued spread.

Sources and image credit

  1. Hentati, Y., Reese, E., Curran, C. C., Miller, E. M., Díaz-Morales, D. M., Kreling, S. E. S., Verocai, G. G., Prugh, L. R., Schell, C. J., & Wood, C. L. (2026). Detection of Echinococcus multilocularis in coyotes in Washington State, USA highlights need for increased wildlife surveillance. PLOS Neglected Tropical Diseases, 20(3), e0013502. https://doi.org/10.1371/journal.pntd.0013502Primary peer-reviewed open-access study published 24 March 2026 under CC BY 4.0. Of 100 coyotes represented across sample types, 37 were positive using next-generation sequencing and/or morphological identification; this was the first confirmation of E. multilocularis in a wild host on the west coast of the contiguous United States.

Image: VJAnderson — coyote photographed in western Washington State on 16 September 2018; Wikimedia Commons; representative regional image, not a study animal · CC BY-SA 4.0 · Source

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