Deadly Tapeworm Detected in Pacific Northwest Coyotes

A dangerous tapeworm, *Echinococcus multilocularis*, has been found in wild coyotes in the Pacific Northwest. This marks the first detection of the parasite in a wild host along the contiguous U.S. West Coast. The tapeworm can cause severe, cancer-like disease in domestic dogs and humans.

Researchers at the University of Washington surveyed one hundred coyotes in the Puget Sound region. They found that 37 percent of the animals carried the parasite. This discovery was published in *PLOS Neglected Tropical Diseases*. The parasite has been expanding its range across North America for about 15 years.

*E. multilocularis* has a complex life cycle. Coyotes and other canids are primary hosts. They can carry thousands of worms in their intestines without showing symptoms. The worms release eggs through feces. Rodents become infected by consuming contaminated food. The eggs develop into cysts in the rodents' livers. Coyotes then become infected by eating these rodents.

Humans and domestic dogs are accidental hosts. People can become infected by ingesting tapeworm eggs. This can happen through contaminated food or contact with infected animal feces. The infection can lead to alveolar echinococcosis. This disease is characterized by slow-growing, metastatic cysts. Symptoms may not appear for five to 15 years. Without treatment, the infection can be fatal.

Veterinarians recommend routine parasite testing and preventative medications for dogs. Dog owners should prevent their pets from preying on rodents or scavenging carcasses. While the parasite is prevalent in local coyote populations, human infections remain rare in the United States. No human cases have been reported on the West Coast.

Genetic analysis indicates the current outbreak is linked to a more infectious strain of European origin. This differs from older cases involving a tundra variant in northwestern Alaska. Scientists are still investigating how this strain became established in North America.