SARCOCYSTIS

Members of the genus Sarcocystis are unicellular parasites found in cysts in muscle of mammals, birds and reptiles.  The resulting disease has often been called sarcosporidiosis.  For years there has been confusion about the biological classification of the genus Sarcocystis.  However, in recent experiments Sarcocystis from sheep was fed to cats and an infection of coccidia was produced in the cats.  Similarly, other researchers have demonstrated that a species of Sarcocystis in cattle is an intermediate stage of a coccidian parasite which will develop in cats, dogs and humans.  Coccidia are a group of common unicellular organisms of vertebrates.  Further work on the life cycles of species of Sarcocystis may indicate that other species are also coccidia.

The cysts of Sarcocystis in muscle may be too small to be visible with the naked eye or may appear grossly as whitish streaks oriented along the direction of muscle fibres.  The larger whitish streaks resemble grains of rice.

Lesions produced when cysts degenerate are seldom considered to have a significant effect on the host except perhaps when there is a heavy infection of heart muscle.

In Ontario, Sarcocystis has most frequently been reported from pintail, scaup, wood duck, ruffed grouse, cottontail, deer and moose.

Species of Sarcocystis in wildlife of Ontario May not be harmful to humans, but until there is a better understanding of members of this genus, infected meat should not be used for human consumption or be fed to dogs or cats.

Selected References:

Frenkel, J.K. 1973.  Toxoplasmosis: parasite life cycle, pathology, and immunology, pp. 343-410.  In: Hammond, D.M. (ed.) with P.L. Long, The Coccidia-Eimeria, Isospora, Toxoplasma, and related genera.  University Park Press, Baltimore.

Fyvie, A. 1966.  A review and current survey of the common diseases and parasites of wildlife in Ontario.  Ont.  Dept.  Lands Forests, Section Report (Wildl.) No. 63. 21 pp.