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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!

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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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