E. multilocularis is a small tapeworm that infects dogs, coyotes, and foxes. It appears to be completely harmless to animals.
So far, human cases in the United States have only been reported in Alaska and Minnesota.
These cases were associated with North American strains of the parasite E. multilocularis, which are considered less contagious than European ones.
Infection occurs when a person unknowingly ingests tapeworm eggs, for example with contaminated food or water. The parasite enters the liver, where it begins to grow.
On ultrasound, it looks like a cancerous tumor. In addition, the symptoms are similar: pain, jaundice, weakness and weight loss.
Echinococcus can live in the human body for up to 10-15 years before manifesting itself.
The first case was discovered incidentally in a 36-year-old woman undergoing routine thyroid monitoring.
The patient had high levels of liver enzymes, so the doctors did an ultrasound to find out what was going on. It was then that they discovered a large neoplasm.
Its location made surgical removal too risky, so the patient is now awaiting a liver transplant.
The second patient, an 82-year-old man, was diagnosed after he developed jaundice. An ultrasound revealed a mass in his liver, which the surgeons removed.
Scientists tested stool samples from more than 400 foxes and coyotes in Virginia and found parasite DNA in two foxes. At the same time, both humans and foxes were infected with the European strain.
Later it turned out that up to 80% of coyotes in one region of the United States are now carriers of the parasite. This shows how efficiently the parasite is spreading.
It is not known exactly how the worm got from Europe to America. However, in Europe, infection remains a rare event, so the individual risk to Americans is minimal.
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