This is a portrait taken of a red fox kit in Lake Clark National Park, Alaska
Tapeworm in fox poop that will slowly destroy your organs is on the rise – Ars Technica
2025-04-23T21:46:59Z
The worm indefinitely proliferates into cystic masses in organs, mimicking cancer.
No matter how bad things might seem, at least you haven’t accidentally eaten fox poop and developed an insidious tapeworm infection that masquerades as a cancerous liver tumor while it slowly destroys your organs and eventually kills you—or, you probably haven’t done that.
What’s more, according to a newly published study in Emerging Infectious Diseases, even if you have somehow feasted on fox feces and acquired this nightmare parasite, it’s looking less likely that doctors will need to hack out chunks of your organs to try to stop it.
That’s the good news from the new study. The bad news is that, while this infection is fairly rare, it appears to be increasing. And, if you do get it, you might have a shorter lifespan than the uninfected and may be sicker in general.
Meet the fox tapeworm
The new study is a retrospective one, in which a group of doctors in Switzerland examined medical records of 334 patients who developed the disease alveolar echinococcosis (AE) over a 50-year span (1973–2022). AE is an understudied, life-threatening infection caused by the fox tapeworm, Echinococcus multilocularis. The parasite is not common, but can be found throughout the Northern Hemisphere, particularly regions of China and Russia, and countries in continental Europe and North America.
In the parasite’s intended lifecycle, adult intestinal worms release eggs into the feces of their primary host—foxes, or sometimes coyotes, dogs, or other canids. The eggs then get ingested by an intermediate host, such as voles. There, eggs develop into a spherical embryo with six hooks that pierce through the intestinal wall to migrate to the animal’s organs, primarily the liver. Once nestled into an organ, the parasites develop into multi-chambered, thin-walled cysts—a proliferative life stage that lasts indefinitely. As more cysts develop, the mass looks and acts like cancer, forming necrotic cavities and sometimes metastasizing to other organs, such as the lungs and brain. The parasite remains in these cancerous-like masses, waiting for a fox to eat the cyst-riddled organs of its host. Back in a fox, the worms attach to the intestines and grow into adults.
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