Particular strain shows no known risk to domestic livestock
By CAROL RYAN DUMAS
New information that a wildlife-threatening tapeworm is prevalent in wolves in Idaho and Montana had some in Idaho's cattle industry concerned the ill effects of the tapeworm could be transmitted to domestic livestock.
The parasite can cause fluid-filled cysts in the lungs and livers of wild hooved animals.
Bill Foreyt, a professor at Washington State University College of Veterinary Medicine who was involved in the study, said no known threat exists to domestic livestock.
"This particular strain in wildlife stays in wild carnivores and wild ruminants," he said.
There is a possibility of transmission, but most domestic livestock are resistant to this particular strain, he said.
"It is not highly pathogenic in sheep or cattle, so I'm not sure there are any concerns," he said. "The biggest concern is in human infection."
The findings by officials with the Idaho Department of Fish and Game, Montana Department of Fish, Wildlife and Parks and the Washington State University were published in the October issue of the Journal of Wildlife Diseases.
In the testing of 123 gray wolves between 2006 and 2008, the tapeworm Echinococcus granulosus was detected in 39 of 63 wolves, or 62 percent, in Idaho and 38 of 60, or 63 percent, in Montana.
While this wild strain is a new parasite in Idaho and Montana, it has not been found in cattle or sheep to date, Foreyt said.
McDonnell, too, knows of no known cases, "but we haven't really tested for the parasite," he said.
Foreyt said that according to the paper published in the Journal of Wildlife Diseases, the tapeworm can be transmitted to domestic livestock, but there is a distinction between strains.
The urban strain, found in domestic dogs in the Southwest, is a threat to domestic sheep as a secondary host and is rare in cattle, he said. The wild strain, now known to exist in Idaho and Montana, stays in the wild.
The parasite is perpetuated by wildlife eating eggs in wolf feces and wolves acquiring the adult tapeworm by eating the cysts in deer and elk.
The authors of the article said it is unknown if the tapeworm was introduced in Idaho and Montana through the importation of wolves from Alberta and British Columbia to Yellowstone National Park and Idaho in 1995 and 1996 or if it existed in other predators and wolves became a new host. But it is now well established in the wolf population in Idaho and Montana, they reported.
"In my opinion, it was likely introduced with wolves when they were brought to Idaho," Foreyt said.
The tapeworm is common in wolves in Canada and is a new parasite here, he said.