TAENIA KRABBEI - MUSCLE CYSTICERCOSIS

The adult stage of Taenia krabbei is known from the small intestine of timber wolves, coyotes, dogs, bobcat, lynx, black bear and grizzly bear.  In Ontario adult T. krabbei have been recovered from timber wolves (Freeman et al. 1961) and black bears (Addison et al. 1978).

The herbivore or intermediate hosts become infected by feeding on vegetation or faeces contaminated with eggs of T. krabbei which have been eliminated from the small intestine of infected carnivores.  The larval or cysticercus stage was once called Cysticercus tarandi, a name which is now synonymized with Taenia krabbei.  Each cysticercus occurs within a small cyst measuring about four millimetres or less in length.  The cysts are located in heart and skeletal muscles of the herbivore hosts.

In North America cysticerci of T. krabbei have been reported mainly from moose but also from wapiti (elk), caribou and mule deer.  In Ontario they are observed frequently in musculature of moose.  Forty of 54 moose from the Chapleau area which were examined during 1963-1965 were infected with cysticerci of T. krabbei in heart muscle.  The number of cysts in heart muscle increased with age of the moose and older moose were more frequently infected than were younger moose.  Large numbers of cysticerci may be found in a single moose.  Samuel (1972) reported 9,531 cysts from a yearling moose collected in Alberta in October, 1971.

T. krabbei has never been reported from man.  For aesthetic reasons, meat heavily parasitized with T. krabbei is often not used for human consumption.  However, people do consume heavily parasitized meat without known adverse effects.  Dogs and wild carnivores should not be permitted access to infected meat.

Selected References:

Addison, E.M., M.J. Pybus and H.J. Rietveld. 1978.  Helminth and arthropod parasites of black bear, Ursus americanus, in central Ontario.  Can.  J. Zool. 56:2122-2126.

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.

Samuel, W.M. 1972.  Taenia krabbei in the musculature of moose: a review, pp. 18-41.  In: Transactions of the Eighth North American Moose Conference and Workshop, Thunder Bay, Ontario.  Ontario Ministry of Natural Resources, Toronto.

Sweatman, G.K. and T.C. Henshall. 1962.  The comparative biology and morphology of Taenia ovis and Taenia krabbei, with observations on the development of T. ovis in domestic sheep.  Can.  J. Zool. 40:1287-1311.