Current News
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Reality Check: Western Wolves and Parasites -- International Wolf Center, 03/12/2010
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In the western United States, a controversy is brewing about parasites in wolves, and the possibility of human infection. International Wolf interviewed Dr. David Mech to shed some light on the issue.
International Wolf: What is this controversy about?
Mech: A letter was recently sent by a Montana legislator to the Montana Environmental Quality Council citing a potential challenge to environmental and human health because Montana wolves are carriers of hydatid tapeworm.
International Wolf: Why is this controversy brewing now?
Mech: The hydatid tapeworm was recently documented in the restored wolves of the western United States. This was no surprise because the worm has long infected coyotes and dogs throughout the Northern Hemisphere. Similarly, the cysts resulting from this worm’s eggs have forever infected the lungs of moose, deer, elk and other ungulates, including domestic animals. However, the hydatid-worm issue has recently become a handy weapon against the wolf. In reality, it’s a tempest in a teapot.
International Wolf: Only a tempest in a teapot?
Mech: Humans at greatest risk of getting the worm are wolf biologists because we handle so many live wolves, carcasses and scats. Nevertheless, no biologist who has been tested, even after having handled thousands of wolves, coyotes and scats, has ever had the parasite.
International Wolf: Are parasites a great problem in wolf populations?
Mech: Wolves, like most other mammals, carry an array of internal parasites. Among them is the tiny hydatid tapeworm (Echinococcus granulosus) whose eggs are released into the environment through the wolf’s anus via scats or otherwise. Hoofed mammals ingest the eggs and grow cysts, usually in their lungs. If a wolf, dog or coyote eats the lungs, larvae in the cyst develop into adult tapeworms in the canid.
International Wolf: Even though there’s evidence to the contrary, is it possible that this might become a problem for humans?
Mech: The tapeworm eggs would only very rarely hatch in a human who ingested them, although there are a few such records, most in the far north where natives’ dogs eat many infected caribou lungs and then pass millions of eggs into the local environment. (See International Wolf, Spring, 2008).
International Wolf: Where does the hydatid tapeworm live, for instance, with no evidence of human infection?
Mech: The worm has long been documented in MN and in Isle Royale National Park. Thousands of people hike, canoe and camp there yearly without any record of infection. I hiked 1,600 miles on Isle Royale during four summers and ate its berries and drank unfiltered water from its lakes, streams and puddles. Perhaps that was reckless, but that was 50 years ago. Still I never contracted the worm.
International Wolf: So you believe the current controversy is merely an attempt to make the wolf look like the bad guy?
Mech: Sorry to say, but yes.
Related links Echinococcus granulosus in wolves in Idaho
Echinococcus granulosus in Idaho Q&A
Montana Fish, Wildlife & Parks Echinococcus Fact Sheet
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