A parasitic tapeworm known as Echinococcus multilocularis — often called the “fox tapeworm” — has been detected for the first time in West Coast wildlife. 

University of Washington researchers discovered the tapeworm, which can cause a rare but potentially deadly disease in humans, in 37 out of 100 coyotes sampled near Puget Sound in Washington State. The findings were published in PLOS Neglected Tropical Diseases earlier this year.

Researchers noted that the presence of the parasite in wildlife does not mean human infections are common, and that the risk to the general public remains low.

“The reason that [cases are] so high in coyotes is because they are regularly eating raw rodents, and that is the primary way for them to get infected,” said lead author Yasmine Hentati, who recently graduated from the UW with a doctorate in environmental and forest science, in a press release.

The study’s genetic testing showed the coyotes carried a newer, more infectious European variant that has become the predominant strain in the US and Canada.

Prior to the 2010s, the parasitic tapeworm was extremely rare in North America, with cases largely confined to the remote islands in Alaska, the authors said.

Over the last 15 years, the parasite has expanded its range, with dog and human infections increasing across the Midwestern US and Canada, according to past reports.

Cases in coyotes have been spreading west from the upper Midwest for several years, and infected animals have been found on the West Coast, according to Dr. Linda Yancey, an infectious disease specialist at Memorial Hermann in the Houston area.

While Eastern Europe has some cases, the infection is very rarely seen in the US, Yancey noted.

Most cases of echinococcosis are diagnosed in patients who immigrated from or traveled to Central and East Asia, the Middle East, and North Africa.

“Worldwide, the area with the highest prevalence of human infections with the fox tapeworm is western China,” Yancey added.

How do humans get infected?

The tapeworm is transmitted among wild animals known as canids — typically cycling from foxes to rodents and back to foxes — and is often referred to as the “fox tapeworm,” Yancey told Fox News Digital.

Humans can get sick from accidentally ingesting worm eggs after handling contaminated soil or eating contaminated food. They can also get the infection by handling a pet that has the tapeworm and then touching their mouth, according to Cleveland Clinic.

Symptoms to watch for

The hallmark of the infection is fluid-filled sacs called cysts, which contain thousands of very small, immature tapeworms that commonly develop in the liver but can spread to other parts of the body, according to the Cleveland Clinic.

The infection often goes undetected for years, or even decades, because the cysts grow at a very slow rate.

There are two main types of forms of the illness: cystic echinococcosis and alveolar echinococcosis, according to the Centers for Disease Control and Prevention. 

With cystic echinococcosis, cysts often develop in the liver and lungs. The body responds by building a protective wall around them as the cysts continue to grow slowly over the years.

Symptoms can include abdominal pain or increased belly size (if it infects the liver) or coughing and shortness of breath (if the lungs are infected). These signs usually do not appear until the cysts grow large enough to press on healthy organs and tissues, according to the CDC.

The infection becomes dangerous when a cyst ruptures — most often due to trauma — and may even lead to death if cyst fluid is released into the body.

Alveolar echinococcosis is a rarer, more lethal form of the infection. It grows into a tumor-like mass that invades and destroys surrounding tissue, typically in the liver, but can also spread to other parts of the body, including the brain. In severe cases, it can lead to liver failure and death, experts say.

“Symptoms of liver failure include fatigue, yellowing of the skin and eyeballs, and abdominal pain,” Yancey cautioned.

This form of the infection can mimic cancer, so it’s important to see a doctor if symptoms are noticed, she added.

Prevention tips

While the overall risk of infection is low, simple precautions can further reduce exposure.

“The most important way to protect yourself from the fox tapeworm is also the simplest: good hand hygiene,” Yancey advised.

She recommends washing your hands before eating and after you have been outside or have handled soil in areas where the tapeworm is endemic.

“For dog owners, prevent your animals from eating wild rodents and make sure all your pets get routine veterinary care,” Yancey added.

The CDC also recommends avoiding contact with wild animals that can carry the tapeworm, such as foxes, coyotes, and stray dogs.

“Routine testing and treatment for worms of all kinds keeps your pups healthy and [keeps] you safe,” Yancey noted.

Fox News Digital reached out to the lead authors of the study, requesting comment.