Tapeworm Cysts

In Deer, Elk, Moose and Rabbits

What Is It?

This condition is caused by larvae of several species of tapeworms or cestodes, including Taenia krabbei, T. hydatagenia or T. pisiformis.  The tapeworms require two hosts to complete the life cycle.  The adult tapeworms live in the gut of a carnivore (wolf, coyote or dog for T. krabbei or mountain lion, lynx or bobcat for T . hydatagenia or T. pisiformis).

Why Is It Important?

In Idaho, the parasite is commonly found by hunters during butchering of wild game, especially mule deer and moose.  It has been reported occasionally in elk, white-tailed deer and rabbits.

Where Is It Located?

The adult worms are located in the intestines of carnivores.  The larval forms, called cystercerci, are commonly found in the muscles of mule deer and moose, and occasionally in white-tailed deer, elk and rabbits.

Who Is Affected By It?

Carnivores like wolves, coyotes, and domestic dogs, mountain lions, lynx, bobcats, and domestic cats can carry the adult tapeworms.  Cystercerci can be found in ungulates (deer, elk and moose) and rabbits.

How Does Infection Happen?

The adult tapeworms in the carnivore lay eggs in the intestinal tract. The eggs pass out in the feces of the carnivore and contaminate plants. The eggs hatch into larvae in the stomach after being eaten by the intermediate host like ungulates and rabbits.  The larvae then travel via the bloodstream to various parts of the intermediate hosts’ body where they form small cysts in the muscle. The life cycle is completed when a carnivore eats meat that contains the cystercerci.

How Do I Keep Myself, My Family and My Pets From Getting Infected?

Humans cannot be infected by ingestion of the cysts of these tapeworms. The cysts can often be removed from the muscle by judicious trimming during butchering.  The meat scraps should not be fed to domestic dogs or cats, as the tapeworms can develop to the adult stage in these animals.  Meat from infected animals is suitable for human consumption. Thorough cooking will kill the cystercerci.  Do not feed carcass trimmings or offal from wild ruminants or rabbits to domestic dogs and cats.  Deworm  domestic dogs and cats annually.

What Is Fish and Game Doing to Help Manage This Disease?

The parasite is widespread in carnivores and ungulates in Idaho.  The parasite does not appear to cause undo harm to its definitive or intermediate hosts. Active management of the parasite is difficult in wild populations.  The public health risk from these parasites is minimal.

Moose rocky riverbank
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Last Updated: January 4, 2013 
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