Specialists are raising concerns about a rapidly spreading tapeworm, known for causing disease, across the United States.

Echinococcus multilocularis, commonly referred to as the fox tapeworm, typically resides in wildlife such as foxes. The tapeworm’s eggs, found in the feces of infected animals, can transmit to other animals and humans who come into contact with them.

Once inside the human body, the parasite multiplies within the liver. This can result in a rare yet severe liver infection called alveolar echinococcosis (AE), which carries the risk of liver failure and can be fatal.

Without treatment, AE has a mortality rate of up to 90 percent.

While Echinococcus multilocularis has been a known public health concern in Europe and Asia, it remains rare in the United States. Nonetheless, it has been found in a limited number of animal cases in states like North Dakota, Ohio, Alaska, Virginia, and Pennsylvania.

A recent study conducted by the University of Washington has documented the presence of Echinococcus multilocularis in coyotes within Washington state for the first time. Out of 100 coyotes examined in the Puget Sound area, 37 were infected with the tapeworm.

It is the first time coyotes in the state have been found to have the tapeworm. Only seven previous reports have been identified in the entire Pacific Northwest, all of which were in domestic dogs.  

The researchers warn that while cases in humans are extremely rare, the study shows E multilocularis may be spreading nationwide. 

The tapeworm mostly lives in wild animals like foxes but can spread if animals or people come into contact with the tapeworm’s eggs, which are present in the feces of those infected

‘This parasite is concerning because it has been spreading across North America. There have been numerous cases of dogs getting sick, and a handful of people have also picked up the tapeworm,’ Yasmin Hentati, lead study author and University of Washington doctoral graduate, said. 

‘The fact that we found it here in one-third of our coyotes was surprising, because it wasn’t found anywhere in the Pacific Northwest until earlier this year.’

The disease is not reportable in the US, which makes it difficult to track and monitor the true prevalence. 

It’s unclear exactly why prevalence may be rising, but experts have noted climate change may have expanded or changed animal habitats, causing coyotes and foxes to interact with more varieties of species.

More transmissible strains may also be spreading. 

The study authors explained that canids such as coyotes can host thousands of parasites in their intestines without becoming ill, as the worms shed eggs that pass in the feces. 

Rodents, however, can become infected by eating food contaminated with coyote feces. Once consumed, parasite eggs migrate to the liver and form cysts that kill rodents. When coyotes prey upon infected rodents, the parasite’s life cycle begins again. 

Humans and domestic dogs are considered accidental hosts. Accidentally ingesting tapeworm eggs often through contaminated food, water or soil, or through direct contact with infected animals can help the parasite enter the human body and begin spreading infection. 

Symptoms in humans may not appear for five to 15 years after exposure, the study authors note, which can make the tapeworm difficult to detect.  

The above CDC graph shows an increase in AE cases over time as the parasite spreads to different areas of the US

AE causes parasitic tumors, primarily in the liver, that can spread to other organs like the lungs and brain in humans. The tapeworm is pictured in the above stock image

AE causes parasitic tumors, primarily in the liver, that can spread to other organs like the lungs and brain in humans. 

While the parasite doesn’t fully mature into cysts, it invades and destroys tissue, leading to liver failure and death. 

Symptoms include abdominal pain, jaundice, weight loss and weakness. 

According to the CDC, people at high risk include ‘trappers, hunters, veterinarians, or others who have contact with wild foxes, or coyotes, or their stool, or household dogs and cats that have the opportunity to eat wild rodents infected with AE’. 

The agency also recommends washing and cooking wild-picked foods carefully, keeping pets away from wild animals and their feces as well as maintaining good hand hygiene, especially after contact with animals. 

‘To minimize the risk of dogs getting infected with E multilocularis, owners should not let them prey on rodents or scavenge their carcasses,’ Guilherme Verocai, study co-author and an associate professor and director of the Parasitology Diagnostic Laboratory at the Texas A&M University College of Veterinary Medicine and Biomedical Sciences, said. 

He also urged dog owners to give pets preventative worm and tick medications and take them to the vet regularly for routine parasite testing.