Fox Tapeworm Found in Coyotes Near Seattle: What You Need to Know
Researchers detected the invasive parasite in 37% of sampled coyotes in Washington’s Puget Sound region, marking a significant expansion of a formerly rare pathogen.
The Discovery
A new study published in PLOS Neglected Tropical Diseases by University of Washington researchers has revealed that the parasitic tapeworm Echinococcus multilocularis—commonly known as the 'fox tapeworm'—is present in a substantial portion of the coyote population near Puget Sound, Washington State. Out of 100 coyotes sampled, 37 tested positive for the parasite.
Genetic testing confirmed that the coyotes were carrying a newer, more infectious European variant that has now become the predominant strain in the United States and Canada.
A Rapid Range Expansion
- Before the 2010s, the tapeworm was extremely rare in North America, primarily confined to remote islands off Alaska.
- Over the last 15 years, the parasite’s range has expanded dramatically. Infections in dogs and humans have been increasing across the Midwestern U.S. and Canada, signaling a significant ecological shift.
How It Spreads & Your Risk
Humans become infected by accidentally ingesting worm eggs from contaminated soil, food, or by handling an infected pet.
Despite the high prevalence in wildlife, researchers state that the risk to the general public remains low. The presence of the tapeworm in coyotes does not mean human infections are common.
"The risk to the general public remains low, and the presence in wildlife does not mean human infections are common."
— Study Researchers
It is important to note that most human echinococcosis cases in the U.S. are diagnosed in patients who immigrated from or traveled to Central and East Asia, the Middle East, and North Africa.
Symptoms: A Slow and Silent Threat
The infection often goes undetected for years due to slow-growing cysts.
There are two main forms of the disease:
- Cystic echinococcosis: Develops cysts in the liver or lungs.
- Alveolar echinococcosis: A tumor-like growth that is far more lethal.
Symptoms may include abdominal pain, coughing, and shortness of breath. In severe, chronic cases, the infection can lead to liver failure.
Prevention: Simple Steps to Stay Safe
- Hand hygiene is critical: Wash hands thoroughly before eating and after handling soil in endemic areas.
- Dog owners should prevent pets from eating wild rodents and ensure they receive routine veterinary care.
- Avoid direct contact with wild canids such as foxes and coyotes.