It Spreads Silently, Kills Slowly, and Just Arrived on the West Coast

A parasitic tapeworm capable of causing a fatal, cancer-like disease has been detected in wild animals along the West Coast for the first time, according to a new University of Washington study. Researchers found the parasite in 37 out of 100 coyotes tested in the Puget Sound region — a detection rate that surprised the scientists who conducted the study and prompted calls for expanded surveillance across the region.

The parasite is called Echinococcus multilocularis, commonly known as the fox tapeworm. When it infects a human or domestic animal, it can produce slow-growing cysts in the liver that behave like a metastatic tumor, spreading to surrounding tissue and, in some cases, to other organs. Without treatment, infection is often fatal. The World Health Organization lists the disease it causes — alveolar echinococcosis — among the most dangerous of the world's neglected tropical diseases, and considers it the third most important food-borne illness globally.

What the Study Found

Researchers from the University of Washington collected samples from 100 coyotes in the Puget Sound area and found 37 carrying the tapeworm — the first confirmed detection of E. multilocularis in a wild host anywhere on the contiguous West Coast. Infected animals were found across a wide geographic range within the Puget Sound region.