By Daily Mail (U.S.) | Created at 2026-06-17 15:59:48 | Updated at 2026-06-19 01:20:16
1 day ago
A potentially deadly parasite that can fester inside humans and dogs for years is spreading across the US, researchers have confirmed.
The tapeworm known as Echinococcus multilocularis is an insidious parasite that lives inside coyotes, foxes and other species in the dog family, passing to humans through contact with contaminated soil, water or food.
A team from the University of Washington has detected the tapeworm in dozens of coyotes near the Seattle area, marking the first time the parasite has been seen in wildlife along the West Coast.
However, researchers noted that the dangerous tapeworms have also been detected spreading east, reaching large portions of New York, Pennsylvania and Vermont in the 2020s.
The tapeworms, which have been a common problem in Northern Plains states such as Iowa, Minnesota, Nebraska and the Dakotas since the 1960s, have also been seen spreading to animals found in Missouri, Kansas, Colorado and Nevada.
Wildlife can carry thousands of the worms without getting sick themselves. The worms produce eggs that are shed in the animals' feces, leading to accidental infections when people and dogs ingest the eggs in nature.
Once infected, the tapeworms cause a serious disease called alveolar echinococcosis, where cancer-like cysts grow in a person's liver and other organs without their knowledge for years.
It can take up to 15 years for serious symptoms to emerge, making an early diagnosis extremely difficult. If left untreated, both people and dogs can die of the slow-growing infection.
A potentially deadly infection to people and dogs has spread to the East and West Coast (Stock Image)
New map reveals recent hotspots of Echinococcus multilocularis tapeworms in the US
When symptoms of the long lingering infection do finally emerge, human carriers would see upper abdominal pain, especially on the right side near the liver.
Patients would also experience weight loss, weakness and fatigue and a yellowing of the skin and eyes known as jaundice - which would occur if the liver was badly infected.
The issues can mimic the signs of liver cancer or cirrhosis because the cysts grow like a tumor and destroy liver tissue.
If the parasites reach the brain, a patient can develop headaches and neurological issues. If they reach the lungs, coughing, chest pain and shortness of breath can develop.
Dr Omer Awan of the University of Maryland School of Medicine told the Daily Mail that 'increased urbanization, deforestation and climate change' have pushed many of the species carrying the tapeworms closer to populated city centers like Seattle.
'Although not common in humans, it can result in severe disease in humans. Without treatment this can be deadly and can affect major organs like the liver, lungs and brain,' Dr Awan warned.
The University of Washington team added that these infections follow a concerning 'cycle of life' as they move from common pests to wild animals to people.
Specifically, rodents eat food contaminated by the eggs and become infected with E. multilocularis. The parasite forms cysts in their livers, which can kill them much faster than it would in humans.
Pictured: Echinococcus multilocularis, a tapeworm spread by rodents and canid species through feces. The parasites can infect both humans and dogs
Scientists say the life cycle of Echinococcus multilocularis moves from rodents to local US wildlife to people and pets ingesting contaminated soil and water
From there, the rats and mice in the wild are eaten by coyotes or foxes, who then spread the parasites wherever they travel in US woodlands through their feces.
Finally, people and pet dogs can easily come into contact with the infected soil. For example, if a dog rolls in contaminated dirt or eats a rodent on a hiking trip, they become a carrier and send the risk of infecting their owner skyrocketing.
Lead study author Yasmine Hentati said in a statement: '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.'
The new study, published in PLOS Neglected Tropical Diseases, provided the first solid proof that E. multilocularis has now spread to wild coyotes along the West Coast of the US.
The team found these tapeworms in 37 of the 100 animals they examined, likely hinting at the parasites being more widespread in the US since the 1990s than scientists thought.
The researchers strongly recommended increasing surveillance of wildlife and more awareness for pet owners and people in regions where the tapeworms have been encountered.
Dr Awan noted that, even though the tapeworms have reportedly spread to several more states over the last five years, a widespread epidemic among humans is still a longshot.
'This is likely not going to become a major public health threat since it is so rare in the US, but certainly something to monitor carefully given zoonotic infections (spread from animal to humans) becoming more common with time,' Awan explained.
