New parasite seen in wolverines raises human health concerns

A newly discovered Trichinella parasite that can persist in freezing temperatures has been detected in wolverines in Canada and could harm First Nations people, researchers fear. If the wolverines spread the hardy parasite to animals that people in the Arctic and subarctic eat, they said, it could spread the disease trichinellosis among humans.

Since wolverines (Gulo gulo) can act as a sentinel species —one that can help researchers detect dangers to the rest of the ecosystem and to humans — Canadian wildlife agencies decided to look into their parasites as they considered what diseases may be affecting First Nations people in the region.

“Wolverines are a species that has a tremendously large range,” said Peter Thompson, a research zoologist with the Agricultural Research Service and one of the lead authors of a recent study on the new disease published in the International Journal for Parasitology. “They go all over the place, almost a 1,000-mile range for wolverines. And they’re scavengers and carnivores, exposed to everything that’s in the environment.”

If wolverines are infected with this parasite, Thompson  said, it is likely that other carnivores and scavengers in the area are as well. This raises a health concern for First Nations people who hunt for food and have been known to eat undercooked meat.

Canadian wildlife managers collected carcasses of wolverines that had either died and were found by wildlife agencies or had been killed by hunters. The carcasses were assayed for parasites by collaborators at the University of Saskatchewan who contacted Thompson to help them detect which Trichinella parasites were in the wolverines.

Thompson already knew of two types of Trichinella that the wolverines could be exposed to: Trichinella nativa and Trichinella genotype T6. The most well-known species, Trichinella spiralis, used to be found in pork, though it is extremely rare in North America today due to modern hygiene practices. The parasite can cause trichinellosis, which results in symptoms like diarrhea, fever and general aches and pains in humans. Trichinella spiralis can be killed by freezing meat or cooking it thoroughly.

The team detected Trichinella species in 70% of the wolverines sampled. But when the researchers began sequencing the genomes, they found a completely novel, freeze-resistant form of the parasite. “The very first test we did to see if we could sequence these things turned up something new,” Thompson said. “I took one look at it and knew we had something different.”

They named the new species Trichinella chanchalensis, which they nicknamed “oddball.” After further testing, they found the new parasite in 14 of the 338 wolverine samples tested. This was the first species of Trichinella discovered since 2012, and the 13^th species of the worm ever identified.

When researchers removed wolverine carcasses from freezers and thawed them, they were able to isolate the parasite from the muscle tissue it inhabits and saw it was still moving. “You know it’s freeze resistant if something comes back to life after it’s in the freezer for two years,” Thompson said.

Since wolverines live throughout the subarctic, including Russia, Finland, Sweden, Canada and Norway — all places that experience very deep freezes — “finding this new species that was also freeze resistant was interesting,” Thompson said.

It is also troublesome, he said, because if a wolverine dies of natural causes, that animal may be left frozen in the Arctic. But when summer comes around, another scavenger can come and eat the carcass and start the infection process all over again, he said.

As far as the researchers know, the disease doesn’t cause symptoms in wolverines. But First Nations people may be vulnerable to contracting the parasite if they consume the raw meat of infected animals. “It would be ideal if they would cook their meat well,” he said. “But changing cultural norms is a difficult thing to do. If we can make them aware of the problem, they can consider changing the way that the treat their meat.”