A disease-causing tapeworm long found in Canada and the Midwest has been found in West Coast wildlife for the first time, University of Washington researchers are warning.
Exposure to the tapeworm, known as Echinococcus multilocularis, can cause cancer-like cysts to form in the liver and other organs years later, and infections can be fatal without treatment.
Although, not all carriers become sick and dogs, coyotes, wolves and other related species can support thousands of tapeworms in their intestines without becoming sick, the researchers say. The latest tapeworm can be transmitted to humans, so its not just animals at risk.
Researchers identified the tapeworm in 37 of 100 coyotes they surveyed in the Puget Sound region in a study published in March.
“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,” Yasmine Hentati, who recently graduated from the school and is the study’s lead author, explained in a previous release.
Infections begin when rodents eat coyote feces that contain the tapeworm’s eggs. Coyotes eat those rodents and the cycle continues.
Dogs may also eat coyote feces and humans are exposed by eating food that’s been contaminated with the eggs.
“The reason that it’s so high in coyotes is because they are regularly eating raw rodents, and that is the primary way for them to get infected. Most domestic dogs are not eating the raw livers of wild rodents,” Hentati said.
When infected, animals and humans can develop the cyst-forming disease known as alveolar echinococcosis, which may not show symptoms for between five to 15 years after exposure.
The rate at which symptoms appear typically depends on the location of the cyst, according to the U.S. Centers for Disease Control and Prevention.
The cysts can be painful, leading to discomfort in the upper abdomen, weakness or weight loss, appearing similar to the symptoms of liver cancer or cirrhosis.
However, human deaths are rare and the overall risk of infection remains low. There were only 41 deaths in humans between 1990-2007, including many who were first exposed outside of the U.S. and people who tend to livestock, Los Angeles County found in 2012.
Further spread into the U.S. may be because neither Canada nor the U.S. require dogs to undergo deworming upon arrival, the Washington researchers say.
Past studies have also suggested that the tapeworm could have been spread via red foxes imported for hunting 100 years ago. But that hasn’t been confirmed.
Some cases in remote Alaska in the 2010s were also tied to a parasite with different origins from the current outbreak, including an older variant than was seen in the Washington coyotes.
The best way to stay safe is to avoid sources of exposure.
Give dogs preventative medication for worms and techs and ensure they go to a veterinarian often who can run tests for parasites.
“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, an associate professor at the Texas A&M University College of Veterinary Medicine and Biomedical Sciences, added.
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