The adult stage of the tapeworm, Taenia hydatigena, has been described from the small intestine of wolves, coyotes, dogs and bobcat.  In Ontario adult T. hydatigena was found in 39 of 58 timber wolves but only in three of 68 coyotes collected from 1957 to 1960 (Freeman et al. 1961).

Infected carnivores eliminate T. hydatigena eggs with faeces.  Herbivores become infected with the intermediate or cysticercus stage by feeding on vegetation contaminated with eggs.  The cysticercus stage was once known as Cysticercus tenuicollis but was later recognized as the intermediate of T. hydatigena.  Cysticerci of T. hydatigena have been found in liver and mesentery of moose, wapiti, caribou, mule deer, white-tailed deer, bighorn sheep, mountain goat, black-tailed jack rabbit and white-tailed antelope squirrel, in addition to domestic goats, sheep, cattle and swine.  In Ontario, deer and moose are the most common intermediate hosts.

Thirty-eight of 51 moose from the Chapleau area which were examined during 1963-1965 were infected with T. hydatigena.  Older moose were more frequently infected and harboured greater numbers of cysticerci than did younger moose.  Most infections of moose and deer are quite light.

Pathological changes may be one or a combination of the following: cysts about one-and-a-half centimetres in diameter, each containing one active larval tapeworm; degenerate cysts in which the larval tapeworm has died and been replaced by caseous and calcareous debris; and meandering streaks which have resulted from the migration of the larval parasite.

As the damage to the liver is generally mild and localized and as the parasite is not transmissible to man, the meat of the moose or deer is safe for human consumption.

   To prevent infection in dogs and to interrupt the life cycle of the parasite, infected entrails should not be fed to dogs nor left available for wild carnivores.

Selected References:

Freeman, R.S., A. Adorjan and D.H. Pimlott. 1961.  Cestodes of wolves, coyotes, and coyote-dog hybrids in Ontario.  Can.  J. Zool. 39:527-532.

Sweatman, G.K. and P.J.G. Plummer. 1957.  The biology and pathology of the tapeworm Taenia hydatigena in domestic and wild hosts.  Can.  J. Zool. 35:93-109.