Submitted to: Journal of Parasitology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/9/1997
Publication Date: N/A
Citation: Interpretive Summary: Infections by the single celled parasites of the genus Sarcocystis are widespread in livestock. Certain species of Sarcocystis cause weight loss, anemia, abortion and death in livestock. The life cycle of Sarcocystis parasites involves 2 hosts - a predator definitive host, dogs, cats, and the prey (intermediate host- cattle, sheep). Scientists at the Beltsville Agricultural Research Center and Northwest Zoo Path, Snohomish, Washington State report for the first time fatal sarcocysts in livers of 2 polar bears from Alaska. The life cycle of the Sarcocystis affecting polar bears is not known. This paper will be of interest to veterinarians and wildlife biologists.
Technical Abstract: Fatal hepatic sarcocystosis was diagnosed in two polar bears from a zoo in Anchorage, Alaska. Gross lesions were icterus and systemic petechiae. Marked microscopic lesions were detected only in the liver and included severe random necrotizing hepatitis with hemorrhage. Only asexual stages of an apicomplexan parasite were detected within hepatocytes, and rare extracellular zoites were seen in foci of necrosis. The parasite divided by endopolygeny, and occasionally merozoites formed rosettes around a central residual body. Ultrastructural features of the merozoites included a conoid and low numbers of micronemes at the apical pole, centrally located nuclei and absence of rhoptries. The parasites failed to react with anti-Neospora sp. anti-Toxoplasma gondii, or anti-Sarcocystis neurona sera. The microscopic and ultrastructural morphology of the parasite are most compatible with an apicomplexan protozoan of the genus Sarcocystis. The life cycle of this parasite in bears is not known.