Fox Tapeworm Spreads Across US, Posing Rare but Deadly Liver Infection Risk
Health experts are raising urgent alarms about the spread of a dangerous tapeworm across the United States. Echinococcus multilocularis, commonly known as the fox tapeworm, primarily resides in wild animals such as foxes but can transmit to humans and domestic animals through contact with infected feces.
The parasite enters the body and multiplies in the liver, leading to an extremely rare infection called alveolar echinococcosis (AE). This condition can cause liver failure and death, with untreated cases resulting in mortality rates as high as 90 percent.
New Study Reveals Spread in Washington State Coyotes
While the fox tapeworm has long been a recognized public health threat in Europe and Asia, it has been relatively rare in the US, with previous cases limited to states like North Dakota, Ohio, Alaska, Virginia, and Pennsylvania. However, a groundbreaking study from the University of Washington has detected E multilocularis in coyotes in Washington state for the first time.
Researchers surveyed 100 coyotes in the Puget Sound region and found that 37 were infected with the tapeworm. This discovery is significant because only seven previous reports existed in the entire Pacific Northwest, all involving domestic dogs.
Yasmin Hentati, lead study author and a University of Washington doctoral graduate, stated, "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. 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."
Challenges in Tracking and Potential Causes of Spread
The disease is not reportable in the US, making it difficult to track and monitor its true prevalence. Experts suggest several factors may be driving the spread:
- Climate change expanding or altering animal habitats, increasing interactions between coyotes, foxes, and other species.
- More transmissible strains of the tapeworm circulating.
- Increased human and pet exposure to wild animals and contaminated environments.
The study authors explain that canids like coyotes can host thousands of parasites in their intestines without showing symptoms, shedding eggs in their feces. Rodents become infected by consuming contaminated food, with eggs migrating to the liver and forming cysts that are fatal. When coyotes prey on infected rodents, the parasite's life cycle continues.
Human and Pet Risks and Symptoms
Humans and domestic dogs are considered accidental hosts. Infection can occur through:
- Accidentally ingesting tapeworm eggs from contaminated food, water, or soil.
- Direct contact with infected animals or their feces.
Symptoms in humans may not appear for five to 15 years after exposure, complicating detection. AE causes parasitic tumors primarily in the liver, which can spread to other organs like the lungs and brain. While the parasite doesn't fully mature into cysts, it invades and destroys tissue, leading to liver failure and death. Common symptoms include:
- Abdominal pain
- Jaundice
- Weight loss
- Weakness
Prevention and Recommendations
According to the CDC, high-risk individuals include trappers, hunters, veterinarians, and others with contact with wild foxes, coyotes, their stool, or pets that may eat infected wild rodents. To minimize risk, experts recommend:
- Washing and cooking wild-picked foods carefully.
- Keeping pets away from wild animals and their feces.
- Maintaining good hand hygiene, especially after animal contact.
Guilherme Verocai, study co-author and an associate professor at Texas A&M University, advised, "To minimize the risk of dogs getting infected with E multilocularis, owners should not let them prey on rodents or scavenge their carcasses." He also urged dog owners to use preventative worm and tick medications and schedule regular veterinary parasite testing.
The researchers warn that while human cases remain extremely rare, the study indicates E multilocularis may be spreading nationwide, necessitating increased awareness and preventive measures to protect public health.
