We describe herein fatal hepatic sarcocystosis in a free-ranging grizzly bear ( Ursus arctos horribilis) cub with apicomplexan infection of the liver and brain, both demonstrating 100% homology for Sarcocystis canis and S. arctosi. Fatal hepatic sarcocystosis in dogs has been etiologically associated with intrahepatic schizonts of S. canis. In black and polar bears, a S. canis-like organism produces schizonts in the liver and massive hepatic necrosis. Although intramuscular sarcocysts, taxa S. arctosi and S. ursusi, have been described in healthy brown and black bears, respectively, they have not been detected in bears with hepatic sarcocystosis, to our knowledge, and it is currently unknown whether bears represent an aberrant or intermediate host.
Keywords: Grizzly bears; hepatic sarcocystosis; liver.