The wolf tapeworm scare

Montana official says it boils down to anti-wolf propaganda-

This is about the 4th time I have written about Echinococcus granulosus, but here is more information.

It made the news in the Bozeman Chronicle today. “Tapeworm in wolves causes stir, but biologists say there’s little to fear.” By Daniel Person.

This week the Montana State official wolf news — “the Wolf ‘Weekly” — contained the following about tapeworms and wolves.

Echinococcus granulosus was recently documented in Montana and Idaho wolves in a peer reviewed journal article, although it is not known for sure where the E. granulosus originated.  It is considered baseline information for wolves in Montana and Idaho.  FWP has recently completed a fact sheet on Echinococcus, a tape worm.  Here is a short summary.

Two different species of the tape worm are known to exist in Montana wildlife and the environment.  The life cycle requires two different “hosts” – typically a definitive canine host where the worms live in the intestinal tract and from which eggs are shed in feces (wolf, coyote, fox, or domestic dog) and an intermediate host (rodents, domestic or wild ungulates, or occasionally a human) that ingests the eggs previously shed in the definitive host’s feces.  In the intermediate host, eggs can turn into cysts in the organs (liver, lung, or brain).  If the organ tissue of an infected intermediate host is eaten by a wild or domestic canine, adult tapeworms can develop in the intestinal track of the canine and be shed in feces.  Cysts are rarely documented in muscle tissue of the immediate host.To become infected, a human must ingest (take into the body) the eggs which are passed with the feces of an infected canine.  Eggs could also be ingested while consuming vegetation or drinking water that was contaminated with egg-laden feces.  Humans could also become infected by not washing their hands before eating if they’ve handled canine scats or contaminated canine fur.  In the rare instance in which larval cysts may occur in muscle tissue of domestic or wild ungulates, thoroughly cooking the meat should kill any larvae.  No reports were found of eggs developing into adult tapeworms in human intestines.

Basic precautions will minimize the risk of human infection by either eggs from canine scats or cysts in domestic or wild ungulate organs.  Dog owners should not allow their dog to consume carcasses of wild or domestic ungulates. If your dog does have access to carcasses, talk to your veterinarian about an appropriate deworming strategy.  Always wash your hands after handling a dog that has access to ungulate carcasses.  When enjoying outdoor recreation, do not touch or disturb wolf, coyote, or fox scat.  Hunters should wear gloves when field dressing a wolf, coyote, or fox carcass, and wash your hands, forearms etc., since they may have come into contact with feces or contaminated fur.

As with handling of any wild or domestic tissues or carcasses, use common sense and wash your hands.  These simple precautions should remove nearly all potential for human infection. [emphasis added]

This is blunt, but for those that are slow, you must never sniff or eat shit, especially that from any carnivorous or omnivorous animal. It is a dangerous thing to do. In addition, wash your hands after handling wildlife and your pets if they go outside. There are many kinds of bacteria and animal parasites you can get from animals. Overall, these are much more of a threat than tapeworms.



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  1. Gregg Losinski Avatar
    Gregg Losinski

    Official information from Idaho Dept. of Fish & Game and Idaho Dept. of Agriculture

    Echinococcus granulosus in Idaho
    January 19, 2010

    What is Echinococcus granulosus?
    Echinococcus granulosus is a parasitic tapeworm (cestode) that requires 2 hosts to complete its life cycle. Ungulates (deer, elk, moose, domestic sheep, and domestic cattle) are intermediate hosts for larval tapeworms which form hydatid cysts in the body cavity. Canids (dogs, wolves, coyotes, foxes) are definitive hosts where larval tapeworms mature and live in the small intestine. Definitive hosts are exposed to larval tapeworms when ingesting infected ungulates. Adult tapeworms, 3-5 mm long, produce eggs which are expelled from canids in feces. Intermediate hosts ingest the eggs while grazing, where the eggs hatch and develop into larvae.
    Can humans get infected with Echinococcus granulosus?
    Yes, it is a known zoonotic disease of humans with a worldwide distribution. Humans can be infected by ingesting eggs from canid feces, usually from a domestic dog. The hydatid cyst is not infectious to humans. There are several treatments for the disease in humans.
    In humans, hydatid cysts usually develop in the liver or lungs. Symptoms depend on cyst location and size. The disease is readily treated with drugs or surgery. In Idaho, at least three reports of human infections with E. granulosus are known; the earliest dating back to 1938. Throughout the world, most human cases occur in indigenous people with close contact with infected dogs.
    Where the parasite is found in wolves and wild ungulates, most wildlife management and public health agencies acknowledge the presence of the parasite, but consider the public health significance to be low. Appropriate use of gloves when handling dog or wolf feces and when skinning and field dressing wolves, coyotes and foxes is recommended by human health and wildlife agencies.
    How do I prevent getting infected with this parasite if I am a hunter, trapper or outdoor enthusiast?
    The potential for human exposure to E. granulosus eggs in wolf feces or fecal contaminated hides is relatively low. Wolf hunters are encouraged to wear latex or rubber gloves when field dressing and skinning wolves in line with the recommendations for handling carcasses of other wildlife as outlined in the IDFG Game Care Brochure (2002). Additionally, wild game meat should always be cooked thoroughly.
    Regular deworming of domestic dogs and good hygienic practices (wearing rubber or latex gloves when handling feces and washing hands after handling feces) by humans in contact with dogs and dog feces are the best methods of control and prevention of the tapeworm in humans.
    Do not feed uncooked meat or organs of deer, elk, moose or sheep to dogs.
    Where is Echinococcus granulosus found? Is it found in Idaho?
    The tapeworm has a worldwide distribution with 2 recognized “biotypes” – the ‘northern’ biotype that circulates between canids (wolf, dog) and wild ungulates (moose, caribou, reindeer, deer and elk) is primarily found in northern latitudes above the 45th parallel. In Idaho, above the 45th parallel corresponds with McCall north. The ‘southern’ biotype circulates between dogs and domestic ungulates, especially sheep. It is endemic in most sheep raising areas of the world.
    Hydatid cysts were found in domestic sheep from Idaho that were sent to California for slaughter in the late 1960’s and early 1970’s.
    In Idaho, hydatid cysts were found in a mountain goat in 2006 and in mule deer and elk in subsequent years in several areas of central Idaho. Adult tapeworms were found in 39 of 63 (62%) wolves collected in 2006-2008 from Idaho. Similar prevalence occurs in Montana. Tests for the tapeworm have not been conducted in coyotes and foxes, and the prevalence rate is unknown.
    Were wolves examined and treated for Echinococcus granulosus before they were released in Idaho?
    All wolves captured in Canada for relocation to Yellowstone National Park and central Idaho were sampled for disease (blood, feces and external parasites) and treated twice for lice (Ivermectin and pyrethrin), roundworms (Ivermectin), and tapeworms (Praziquantel).
    What is the significance of Echinococcus granulosus to wildlife and livestock?
    Normally, Echinococcus granulosus is not harmful to canids or felids. Heavy infections may be associated with diarrhea or poor body condition. In ungulates, the presence of large numbers of hydatid cysts can lead to respiratory difficulty. The presence of hydatid cysts in livestock at slaughter is generally not of concern, and if present, is trimmed from the edible product.
    Where can I go to learn more about this parasite?

  2. Larry Thorngren Avatar

    Those wonderful Yellowstone wolf biologists that routinely pose with the wolves they have darted need to read this. I have yet to see a photo in books and articles featuring these biologists posing with wolves, that show them taking any kind of precautions like gloves. All of them need to be checked for the tapeworm hyatid cysts which can grow as large as an orange in brain tissue.

  3. Jay Barr Avatar
    Jay Barr

    You’d think that if this really was of any concern/danger, somebody involved with the NRM wolf projects would have contracted this by now. To my knowledge nobody has. No that it would become public knowledge.

  4. JB Avatar

    “Humans can be infected by ingesting eggs from canid feces…”

    There you have it. You’ll be fine if you avoid eating dog/wolf sh|t. I guess those biologists are smarter than you thought, Larry. 😉

  5. Jay Avatar

    Make the wolves improve their hygiene, not the biologists wear gloves!

  6. SEAK Mossback Avatar
    SEAK Mossback

    This parasite is fairly widespread in much of Alaska but has seldom made any news that I’ve noticed. I personally encountered it 5 or 6 years ago. I shot a deer high above my house near dusk, and was in somewhat of a hurry to get moving down before dark. I reached with one hand between the lungs for the heart, thought I had it and began to cut with my knife but was shocked when it burst and showered me with clear fluid. When I examined the burst cyst, I had a pretty good idea what it was – remembering a class I’d taken on natural history in Alaska back in 1975. I was careful when I got down to keep our dog from greeting me – and then put my clothes straight in the washer. I sent the cyst off to the state veterinarian, Dr. Kimberly Beckman, who confirmed it was E. granulosus, the first documented case in Southeast Alaska (although common in the interior).

    Oddly, wolves had been only occasional visitors on the 50,000 acre island, although common on the nearby mainland. However, there had in recent years been a brief flurry of wolf activity beginning with a loner trotting around for 2 or 3 years, then suddenly two tracks together one fall and then a full pack of 2 adults and 5 pups in summer 2000. A trapper caught all seven in short order in January 2001 (after many hikers, kayakers and even tourists on larger vessels had seen them – much outrage and controversy ensued). They had been gone over 2 years when I got the infected deer, but Dr. Beckman said they were very likely the agent – and in fact they had laid down a noticeable amount of scat during their tenure. Also, the eggs are apparently quite resistant to the elements and who knows how long it had been since they were ingested by the deer?

    ADF&G publishes cautionary information but otherwise the parasite seems to have hardly penetrated the consciousness of hunters or the public in general. I’m curious about just how many cases have been documented of humans being infected in North America. I’m acquainted with a former graduate student who said his major professor (an authority on wildlife parasites at the University of Alaska) had some doubt that the form we have in this part of North America is very readily transmitted to humans. I have never heard of a case in Alaska, where one would think transmission to humans would occur at least occasionally, given how many village dogs have access to both ungulate organs and humans. At least a hiker or two must have handled wolf scat before eating a sandwich. I do, however, remember hearing about cases of E. multilocularis which cycles between foxes and rodents and is generally fatal in humans if untreated (It seems arctic fox trappers on St. Lawrence Island had a habit of holding the tails in their teeth while pulling the skins forward). However, the examples I saw on the internet of hydatid cysts (E. granulosus) in humans were mostly from sheep and goat herding regions in Europe and the Middle East where herding dogs and their charges are apparently both hosts (as well as potentially people). But that may be a slightly different form.

  7. Jay Avatar

    All this is, is the folks making a pathetic example of grasping at straws. They’ve tried every other tactic, now they’re trying to scare you that you’re going to get a little alien parasite burrowing through your body. If we’re going to demonize wolves for spreading disease, lets talk about mice and Hanta virus, raccoon, skunks, foxes, etc. and rabies, mountain lions and plague, rabbits and tularemia, bears and trichina worms, and so on, and so on….

  8. mikarooni Avatar

    Gosh, I thought Rehberg had something to do with it.

  9. Ralph Maughan Avatar

    You can get a lot of infections from the outdoors, but I’d say the most important in the Western and Northern United States are Giardia, West Nile, Hantavirus, Lyme Disease, other tick borne diseases, and wild E. coli (not the lethal type — E.coli O157 — just the kind that comes from wild animals).

  10. Jay Avatar

    Maybe George Dovel and his band of fearless “outdoorsman” will be too scared to go in the woods now…we can only hope.

  11. Larry Thorngren Avatar

    Any wolf or dog that you encounter has just recently been licking its’ behind or sniffing the behind of their pack mates. That is what they do. Each passed segment of a Tapeworm is full of thousands of eggs. I have seen these segments stuck to the fur near the anus of infected dogs.
    The cyst found in meat does not contain eggs. It develops into a mature tapeworm in the canid’s intestine if eaten. Tapeworm eggs are very sticky and can be found on the fur on any infected dog or wolf. You don’t have to eat shit to get infected. If you don’t wash before you eat your sandwich after handling wolves you are at risk for infection. Letting your dog lick your face after it just cleaned its’ behind with its’ tongue is not a good idea either.
    When I taught the chapter on tapeworms to my high school biology students,I would ask how many of them had a dog that drug its behind around on the carpet to itch itself. Many of them reported that they did. I suggested that they get their dogs wormed and shampoo the carpet. If the dog was infected with tapeworms, anyone who dropped a cookie on the carpet and ate it might end up with a cyst. Many people are infected without being aware of it.
    Common sense and a little personal hygiene provide adequate protection. The photos that I have seen of gloveless wildlife biologists handling wolves and other wildlife suggest they have little of either.

  12. NW Avatar

    I wish I’d had a camera when a charismatic wolf biologist was gesturing with a scat in one hand and a sandwich in the other. I don’t think he ever got Echinococcus. Somebody taught me to wash my hands before I eat and that’s probably as good as struggling with rubber gloves in the field. Snow and Purell.

  13. Ralph Maughan Avatar

    Internal worms have always given me more creeps than any other aspect of nature.

    Nevertheless, it is a bit like fear of spiders or lack. It can be overblown as some are trying to do for purely political purposes. It can also be stupidly ignored as when that black widow finally nails you as you reach deep into the wood pile with your bare hands.

  14. Douglas Henderson Avatar
    Douglas Henderson

    From what I’ve read about tapeworm infection, another vector for spreading the intestinal infection by ingestion of tapeworm larva comes from a predatory eating fleas. The fleas ingest the tapeworm eggs from their host mammal, where the larva develop and the fleas are then ingested as happenstance of the host animal being eaten.

    I think one is as likely to be exposed to tapeworm larva from cats bringing mice into the house as encountering larger prey and predators.

    The wolf/tapeworm stories seem to be an example of scare tactics, although ingesting tapeworm eggs from any source is a potential serious problem, one very different than an intestinal infection of larva that grow into mature tapeworms. The recent story from Butte news station KTVM, by passing on the idea that wolves are introducing something new in the region is, in my opinion, irresponsible.

    1. Ralph Maughan Avatar


      Yes, it’s the larval tapeworm that is by far the more dangerous, and there are number of such species where humans (and/or other animals) are the dead end for tapeworms. Thus only larva develop. Humans are the definitive host for the following, and so, while disgusting, these are less dangerous. I got this list from Wikipedia: Taenia saginata (beef tapeworm)/Taenia asiatica/Taenia solium (pork tapeworm) (Taeniasis/Cysticercosis) · Hymenolepis nana/Hymenolepis diminuta (Hymenolepiasis– rat tapeworm); Diphyllobothrium latum (Diphyllobothriasis — fish tapeworm). This means humans grow the big mature worm. The pork tapeworm can also cause a larval infestation.

      There are a number of species of tapeworms for which the dog is the host of the mature worm but can also infest humans with mature worms or larva such as in Echinococcus. Getting infected from wolves (or sheep!) is very rare, but dogs, being so much more numerous and often in close contact with humans, are far more likely the source of any human infestation. I am amazed that some people sleep with their dog or dogs that are allowed on wander freely outdoors.


Dr. Ralph Maughan is professor emeritus of political science at Idaho State University. He was a Western Watersheds Project Board Member off and on for many years, and was also its President for several years. For a long time he produced Ralph Maughan’s Wolf Report. He was a founder of the Greater Yellowstone Coalition. He and Jackie Johnson Maughan wrote three editions of “Hiking Idaho.” He also wrote “Beyond the Tetons” and “Backpacking Wyoming’s Teton and Washakie Wilderness.” He created and is the administrator of The Wildlife News.

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