If a Northern Rocky Mountain gray wolf has a daily to-do list, it may look like this:1.) Avoid hunters, 2.) Maintain territory, 3.) Find prey, 4.) Get de-wormed.
According to a new study out in the October issue of the Journal of Wildlife Diseases, three-millimeter-long tapeworms known as Echinococcus granulosus, are documented for the first time in gray wolves in Idaho and Montana. [Editor’s note: the reference here to a first documentation pertains to peer-reviewed literature.] And the authors didn’t just find a few tapeworms here and there… turns out that of 123 wolf intestines sampled, 62 percent of the Idaho gray wolves and 63 percent of the Montana gray wolves were positive. (Ew!) The researchers wrote: “The detection of thousands of tapeworms per wolf was a common finding.” (Again… Ew!!) This leads to the interpretation that the E. granulosus parasite rate is fairly widespread and established in the Northern Rocky Mountain wolves.
The tapeworms themselves are not new. Gray wolves in Canada and Alaska are known to be infected with them. In fact, previous studies indicate that a 14 to 72 percent infection rate is normal. But the study authors report that this is the first time that a specific biotype of E. granulosus has been detected in not only wolves of Idaho and Montana, but also wild herbivores. The parasite needs both types of animals to complete its life cycle.
The two biotypes of North American E. granulosus are known as “northern” and “domestic.” And up till now, the northern biotype has not been reported in any wild species in Idaho or Montana — but this is the type they found in the Yellowstone gray wolves. The northern biotype needs wild cervids as an intermediate host (deer, elk, moose and caribou), but wolves are it’s main squeeze. The domestic biotype also uses wild ungulates as an intermediate host (it prefers sheep), but dogs are it’s main squeeze.
It is fair to ask whether the reintroduced canids picked them up from dining on already-infected wild prey in the lower 48 states. It’s truly unclear where the worms came from — were they already here, but not documented? Here is what they do know: 1.) the tapeworm biotype matches what is known to occur in northern latitudes of N. America ; 2.) the percentage of the infected population appears, upon the first sample, to match the known infection rate in Canada and Alaska for gray wolves.
Interestingly, the researchers also document finding E. granulosus in elk and mule deer in the study states, two of the top menu items for any self-respecting gray wolf. The authors concede it is nearly impossible to pin point the worm’s origins:
“It is unknown whether the parasite was introduced into Idaho, USA, and southwestern Montana, USA, with the importation of wolves from Alberta, Canada, or British Columbia, Canada, into Yellowstone National Park, Wyoming, USA, and central Idaho, USA, in 1995 and 1996, or whether the parasite has always been present in other carnivore hosts, and wolves became a new definitive host.”
Is this a simple case of an absence of data, or is this an emerging pathogen in the lower 48? The fact that our reintroduced wolves have the northern biotype would appear to lean toward an interpretation that the Yellowstone wolves arrived with the tapeworms. But part of the reintroduction management measures included de-worming the candidate wolves. The authors suggest that gray wolves which naturally recolonized parts of Montana from British Columbia could have brought the tapeworms with them, and supplanted them in to the wild herbivores which then passed them on to the reintroduced wolves.
The good news is that the northern biotype poses a low threat to humans, if they were to ingest the worms. But it may pose a threat to domestic dogs, which can serve as the host. Something to be on the lookout for if you are a dog owner living near known wolf territories in these two study states.
Bottom line, if you are a tapeworm, wolves just may be your mother lode of a sugar mama… Think about it, they bring you plenty of nutritiously dense food, plus they travel long distances and are biological dispersers so they can deposit you in a wide range of new environments. Not a bad lifestyle for a three-millimeter long wriggly bit of tissue that can’t do these things on its own.
ADDENDUM, MARCH 8, 2010:
I some how missed Ralph Maughan’s contribution to this issue, but he typed up a great post examining the *relative risk* of this organism to humans — something that most reports have completely missed the mark on; and something that most anti-wolf advocates have completely ignored. One thing I love about science is that the truth always comes to light, no matter how much some people may try to distort the facts and cherry-pick certain findings to advance their own agenda. Go read Ralph’s post, “The wolf tapeworm scare – it all boils down to anti-wolf propaganda.”
William J. Foreyt et al. 2009. Echinococcus granulosus in Gray Wolves and Ungulates in Idaho and Montana, USA. Journal of Wildlife Diseases. 45(4): 1208–1212
Suggested reading: CDC page on Echinococcocis