Ultrastructure of the cyst wall and merozoites of Sarcocystis from moose (Alces alces) in Alberta, Canada.

Two distinct types of cysts of Sarcocystis from the musculature of moose (Alces alces) were compared by electron microscopy. The fusiform Type A cysts differed from the spherical Type B cysts in the appearance and thickness of the primary cyst wall, organization of cyst interior, and the presence of a secondary cyst wall around Type B. The respective merozoites also differed in size as well as in the number of rhoptries and diameter and arrangement of micronemes. Comparison of the ultrastructure of the moose sarcocysts with those described from other ungulates revealed substantial differences. It appears that two hitherto undescribed species of Sarcocystis are present in moose although cross-transmission and additional life cycle studies are necessary for a complete description.