Public health researchers are identifying more and more cases of a rare, potentially fatal parasitic infection in Alberta.
The parasite, a tapeworm called Echinococcus multilocularis, is mostly found in animals but can infect people and cause a tumour-like growth on the liver that can be deadly if it’s not treated early enough.
A team of researchers at the University of Alberta and University of Calgary, along with international partners, described seven documented cases of the parasite infecting people in Alberta in a letter to the New England Journal of Medicine published Wednesday.
They’ve since identified even more cases since submitting their report, bringing the total to 13, said Dr. Stan Houston, a professor of medicine and public health at the University of Alberta and one of the co-authors of the letter.
WATCH: A rare disease once limited to Europe and Asia has been diagnosed across Alberta. As Cami Kepke reports, University of Calgary researchers say tapeworm disease is still uncommon, but can have serious consequences.
“To put that in perspective, there have been only two proven recorded cases of this disease in North America in the previous 86 years,” Houston said.
“Now we have 13 proven cases in five years in just one area of Alberta. So obviously there’s something very new happening.”
The researchers are particularly concerned about a European strain of the parasite appearing in North America, as that strain appears to infect humans much more readily than the usual North American version, Houston said.
“We know that the European strain has caused disease in humans and has been well recognized for 150 years,” he said. “And the strain that has been prevalent before in North America, we just didn’t see human cases.”
WATCH: Risk of ‘tumour-like’ tapeworm on the rise in Alberta (August 2018)
This new strain isn’t just appearing in travellers, either. Many of the cases the team identified were in people who have never been to Europe, suggesting that they’re getting infected at home, where this strain has taken hold.
The tapeworm itself is tiny – just a few millimetres long. Adult tapeworms live in the intestines of canids – typically coyotes or dogs in North America, or foxes in Europe. When the dog poops, it also sheds tapeworm eggs in its waste, which are typically consumed by rodents.
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These rodents act as hosts for the tapeworm larvae, and get eaten in turn by coyotes, dogs or foxes, perpetuating the worm’s life cycle, Houston said.
But humans can pick up the tapeworm eggs too, by eating mushrooms or plants contaminated with the eggs, or by touching dogs who may have rolled in feces, Houston said. If people somehow ingest the eggs, they can grow inside the human body, too.
The embryos usually attach to the liver, where they grow into multi-celled cysts that look a lot like a tumour, Houston said. Once it starts in the liver, he said, “Then it grows and invades and can spread like a cancer.”
Symptoms can take up to 15 years to appear, he said, and people who are immunosuppressed might be more prone to developing the infection.
According to Ottawa Public Health’s website, some symptoms of the disease might include jaundice or pain, but in many cases, the cysts are discovered by accident when a patient is scanned for some unrelated medical issue.
The infection can be treated, but it requires surgery to remove the mass of cysts or taking anti-parasitic medication for a prolonged period – possibly for the rest of the patient’s life.
While Houston cautions that the parasitic infection is still very rare, there are some things you can do to prevent it. He recommends carefully washing any mushrooms or produce that you pick from your garden or the ground, and also washing your hands after petting dogs.