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What You Need to Know About Worms

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a hydatid cyst in lung tissue. CDC photo a hydatid cyst in lung tissue. CDC photo

on the Game Trail

 Echinococcus granulosus. The genus species name for a parasitic tapeworm that seems to be making the rounds in the media these days. Others may call it by the much easier name Hydatid Worm or Hyper Tape Worm. Either way, it’s becoming a popular side-car discussion when wolves are the topic. Unfortunately some fear mongers have used misinformation about the life cycle of this parasite causing some panic and confusion.

Working with and around wildlife always poses a health risk due to the exposure of bodily fluids, fecal matter, and organ tissues. As one of my friends says, “People who work around wildlife are going to die some day!” Well, you can’t deny that! It’s his smartass way of saying there are inherent risks in everything we do in life, so know the dangers and have a plan to reduce those risks.  

Here are some facts about E. granulosus in the hope that I reduce the concern of some people, while also raising awareness of the dangers of this parasite.

Echinococcus granulosus is a parasitic tapeworm that requires two hosts to complete its life cycle. Ungulates (deer, elk, moose, domestic sheep, and domestic cattle) are intermediate hosts for larval tapeworms while 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 canids pass in their feces. Intermediate hosts ingest the eggs while grazing, where the eggs hatch and develop into larvae.  

Okay, you say, what that heck does that mean, Matt? Yes, humans can get the tapeworm but it has to take a very specific path in order for them to do so. One of the most common sources of inflection of this parasite in humans is exposure to infected dogs that are passing eggs in the feces. So, if you are feeding your dog wild game meat, stop it. Your pet dog is a definitive host of that tapeworm and will expose you to the eggs. The eggs are pretty tough and are relatively resistant to environmental conditions so they may be present in dried feces and in the immediate area around the feces.

To make things a little more confusing, but very important to discuss, there are two biotypes of E. granulosus. The northern or sylvatic biotype circulates between canids (wolves, dogs coyotes) and cervids (deer, elk, moose) is a well-documented disease of humans and is found throughout the world. According to health experts the human infection is relatively benign, causing cysts most commonly found in the liver and lungs. 

The second biotype of E. granulosus is a domestic variety and circulates between dogs and domestic ungulates, especially sheep. It’s endemic in most sheep raising areas of the world including the southwestern U.S. and Central and South America, among some other places. Human infection with this biotype is known to be much more severe than our northern biotype, largely due to its brain involvement.

There are a couple of potential sources of E. granulosus in Idaho. Prior to wolf introduction it was present at low prevalence in coyotes, foxes and other canids and cycling in wild cervids. The wolf introduction has spread the parasite with the obvious rapid expansion of wolf populations.  The second potential source is that the parasite has always been present in domestic dogs and sheep and spilled over to wolves and cervids following wolf introduction. The third potential source is that the parasite was introduced with the wolf introduction despite the anthelminthic (drugs that expel worms) treatment of captured individuals prior to their release in Idaho. And lastly, the parasite was introduced with natural migration of wolves into Idaho from Canada and Montana.

Folks always ask me if we have some treatment plan for E. granulosus and other wildlife diseases. I guess it’s a sign of the times when we think there is a magical pill out there that can we can administer to all wildlife.  Control of this parasite is extremely difficult if not darn near impossible. One of the best safety measures we can do is follow our veterinarian’s advice and give our dogs regular anthelminthic treatment, or de-worming treatment. Secondly, as I stated earlier, do not allow your dog to consume any wildlife parts.

The potential for human exposure to the eggs of E. granulosus in the feces of infected wolves or fecal contaminated hides is low but possible. A majority of people in Idaho have minimal contact with wolf feces with the exception of wolf hunters. Wolf hunters are encouraged to wear latex gloves when field dressing and skinning wolves. I would also caution hunters to follow these safety steps when handling any wildlife; Do not harvest obviously sick animals, wear latex gloves or rubber gloves when field dressing all wildlife, cool the carcass of the animal quickly as possible, clean the animal as soon as possible, and cook the meat thoroughly. 

I have handled a lot wolves and these critters do not take pride in cleanliness; matter of fact, they are the most vile animal I have ever been around. Common sense would dictate a little precautionary action before handling these critters.

I hope this helps you to remain healthy in your outdoor adventures. If you have any concerns or need information on this or other parasites you can always call and ask us. If we don’t have the answer for you I bet our wildlife veterinarian, Dr. Mark Drew, could answer your question. And thanks to Dr. Drew for some information in this article.

I hope this New Year brings much happiness and good health for everyone. Don’t forget to purchase a 2012 license if you plan on doing some fishing or hunting this winter!

Leave no child inside!

Subscribe to comments feed Comments (8 posted)

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rob 01/18/2012 18:44:55
I read on * hunting forum that there was * 192 pound wolf killed in Idaho? I guess this is false. Why are some people claiming that the reintroduced wolves are * non native species? I myself don't know why gray wolves in Canada would be different than gray wolves anywhere else. According to Ron Nowak's work, he found that the reintroduced wolves were already naturally coming into Idaho on their own from Canada, but still people claim that canadian wolves are * non native species. I hope after the Idaho wolf hunts are over in Idaho. idfg will come out with the weights of the wolves killed by hunters just to show the public that these wolves aren't as big as some are making them out to be. Some people are worried that too many wolves will be killed, but do you think the wolf population will do just fine? I have read what Dr. William Forety and Dave Mech have said about this tapeworm and they both agree it poses * low risk to humans. my last question is what do you think about those who accuse wolves of killing elk and deer for sport and not eating any of their kills? thanks matt
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rob 01/15/2012 19:09:00
Hello Matt, are you familiar with the work of dr. robert rausch? would you say that some are using this tapeworm as nothing more than a scare tactic to scare people because they don't like wolves? are the wolves in Idaho non native canadian wolves and do they reach 200 pounds like some in idaho are claiming?
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Matt Haag 01/16/2012 17:43:02
HI Rob - I am unaware of Dr. Robert Rausch however I will spend the time to read up, thanks. Yes some are using this tapeworm as * scare tactic for reasons I do not know, I suppose that is up to the individual. I handle * lot of wolves and spend * good amount of time outdoors in wolf country and I'm more worried about belligerent moose, ticks, and bald face hornets than EG tapeworm. I can't speak for everybody nor am I trying to belittle the health consequences of EG of. any parasite.

* wolf is * wolf, is * wolf, regardless if they are form Canada, Alaska, Minnesota, or Montana. They don't know our borders and disperse large distances to breed. I have not seen * large male wolf over 130lbs and that is pretty consistent across the state, region, and northern Rockies. It also is consistent with older trapping records from Alaska, MT, ID,etc from the early 1900's. Yes there are pictures floating around the internet of 200lb wolves none which can be verified. Biological speaking it would not behoove * wolf that relies on it's ability to chase and overtake an ungulate to be that large, similar to the reason we don't see 350lb running backs in the NFL.
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David Rowell 01/14/2012 07:38:48
If the ungulate game meat is cooked thoroughly, is it safe for my dog to eat it, then? Is "medium rare" (135-140 degrees F) cooked thoroughly enough to make it safe for humans?
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Matt Haag 01/14/2012 10:08:49
David - I still would not feed wild game meat to your dogs regardless if it has been cooked. If you do decide to do that be sure to de-worm your pets according to your Vets recommendation. 150 degrees is the cut off for all parasitic critters.
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Matt Haag 01/16/2012 17:47:29
David - I forgot to add that consuming the cysts in ungulate meat, at least for humans, is not the same as eating the active eggs of the EG tapeworm found in wolf or dog scat. The cysts do not infect you with EG. I still cook my game meat medium rare, at the same rate I can't tell people how to cook their meat, I can only suggest what the USDA and FDA recommend. Thanks again David.
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Kay Turley 01/13/2012 18:45:39
There are so many wolves in this area, how does one know. We don't touch them and I certainly would not go somewhere they are. But the fact of the matter is, there is scat from new to old everywhere. And that is how it is passed. In Idaho the numbers are 67% of wolves tested have EG. In * rural area like most of us are, how do we protect ourselves and NO I am not moving.
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Matt Haag 01/14/2012 10:11:44
Kay - there are so many wolves in this area compared to what? And how does one know . . . what? Unless you are handling wolf scat or eating it, I wouldn't worry all that much. If you read the article, there are tips on how to protect yourself.
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Author info

Matt Haag Matt Haag is an Idaho Fish and Game Conservation Officer.

Tagged as:

ungulates, wolves, wildlife, hunting, Matt Haag, The Game Trail, Echinococcus granulosus, tapeworm, hydatid worm, hyper tapeworm, canids, sheep, wolf introduction, Dr. Mark Drew

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