Tapeworm Threats: Emerging Cases in Wildlife and Human Health

Fox Tapeworm Detected in Washington State Coyotes

A new study reveals a troubling expansion of a dangerous parasite into the Pacific Northwest.

"The risk to the general public remains low, but the presence in wildlife does not mean human infections are common."

A study published in PLOS Neglected Tropical Diseases by researchers at the University of Washington detected the parasitic tapeworm Echinococcus multilocularis, commonly known as the "fox tapeworm," in 37 out of 100 coyotes sampled near Puget Sound, Washington State.

Genetics and Geographic Spread

Genetic testing indicated that the coyotes carried a European variant of the tapeworm that has become predominant in the United States and Canada. Prior to the 2010s, the tapeworm was reported primarily in remote Alaskan islands. Over the last 15 years, its range has expanded dramatically, with infections in dogs and humans increasing across the Midwestern U.S. and Canada.

Transmission and Human Risk

Humans can become infected by accidentally ingesting worm eggs from contaminated soil, food, or by handling an infected pet. According to the study, 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 and Prevention

The infection often goes undetected for years due to slow-growing cysts. Two main forms exist:

• Cystic echinococcosis (cysts in liver or lungs)
• Alveolar echinococcosis (tumor-like growth, more lethal)

Symptoms may include abdominal pain, coughing, shortness of breath, and in severe cases, liver failure.

Prevention recommendations include:

• Hand hygiene before eating and after handling soil
• Preventing pets from eating wild rodents
• Ensuring routine veterinary care
• Avoiding contact with wild canids such as foxes and coyotes

Human Case Misdiagnosed as Brain Cancer in Spain

A 60-year-old man from Castellón, Spain, was treated for a parasitic brain infection that was initially misdiagnosed as metastatic cancer.

"An absence of travel history should not exclude NCC from the differential diagnosis of ring-enhancing brain lesions."

Presentation and Diagnosis

The patient presented with two weeks of progressive headaches and mild behavioral changes. CT scans showed multiple ring-enhancing brain lesions initially thought to be metastatic cancer. Whole-body scans, colonoscopy, and specialized imaging did not find cancer elsewhere.

A more detailed MRI revealed fluid-filled cysts containing tapeworm heads. A blood test confirmed neurocysticercosis caused by Taenia solium larvae.

Transmission and Treatment

The patient had no travel history to endemic areas, suggesting possible local transmission. He was treated with albendazole, praziquantel, and corticosteroids and recovered without complications.

Background on Neurocysticercosis

Neurocysticercosis (NCC) is a parasitic infection of the central nervous system caused by the pork tapeworm. Infection occurs when microscopic tapeworm eggs are ingested, leading to larvae that can form cysts in the brain.

In non-endemic regions like Western Europe, locally acquired NCC is rare, with only 18 confirmed cases between 1990 and 2011. In the US, less than 2% of NCC cases are domestically acquired.

The case emphasizes that even in regions where metastatic cancer is statistically more likely, parasitic infections should remain on the differential diagnosis for ring-enhancing brain lesions.