Tiny Terror: Tapeworm Spreads to Pacific Northwest

A dangerous tapeworm, Echinococcus multilocularis, has officially arrived in the Pacific Northwest, marking its first detection in wild hosts along the contiguous U.S. West Coast. Researchers from the University of Washington discovered the parasite in 37% of coyotes sampled in the Puget Sound area, a finding published in PLOS Neglected Tropical Diseases.

This tapeworm relies on a cycle involving wild canids like coyotes, which shed eggs. Rodents ingest these eggs, forming cysts that can be fatal. When infected rodents are consumed by canids, the cycle continues. Humans and dogs can accidentally ingest the parasite's eggs, often through contaminated feces.

In humans, this can lead to alveolar echinococcosis, a slow-progressing disease causing liver tumors and potentially fatal outcomes. The World Health Organization ranks it as a top food-borne illness. Dogs face risks from ingesting feces or infected rodents. Experts urge dog owners to prevent pets from hunting rodents and to ensure regular veterinary check-ups and deworming. While no human cases have been reported on the West Coast, seven dogs in Washington, Oregon, and Idaho have been infected since 2023, underscoring the growing threat from this European strain.