Submitted to: Journal of Parasitology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: October 8, 2001
Publication Date: N/A
Interpretive Summary: Parasites of the genus Sarcocystis are single-celled organisms. Some species of Sarcocystis cause abortion neurologic diseases, and retard growth of livestock. Sarcocystis canis causes a fatal liver disease in several species of animals including sea mammals. Its life cycle and sources of infection are unknown. Scientists at the Beltsville Agricultural Research Center and University of Barcelona, Spain report the first case of severe hepatitis in a dolphin associated with Sarcocystis canis. This is the first report of this parasite in this host and first report outside of the United States. The results will be of interest to parasitologists, pathologists and biologists.
Fatal hepatic sarcocystosis was diagnosed in a striped dolphin (Stenella coeruleoalba) from the northeastern Spanish Mediterranean coast, based on pathologic findings, and the microscopic and ultrastructural characteristics of the intralesional parasite. Main gross lesions were icterus, subcutaneous hemorrhages, and hepatic congestion. The most prominent microscopic lesions consisted of severe acute multifocal to coalescing necrotizing hepatitis with cholestasis and intralesional protozoa. There was severe chronic pancreatitis with generalized distension of pancreatic ducts by hyaline plugs and adult trematodes. Only asexual stages of the protozoa were found. The parasite in the liver divided by endopolygeny. Schizonts varied in shape and size. Mature schizonts had merozoites randomly arranged or budding peripherally around a central residual body. Schizonts were up to 22 m long and merozoites were up to 6 m long. Ultrastructurally, merozoites lacked rhoptries. This parasite failed to react by immunohistochemistry with anti-Toxoplasma gondii, anti-Neospora caninum and anti-Sarcocystis neurona antibodies. The microscopic and ultrastructural morphology of the parasite were consistent with Sarcocystis canis, so far described only from animals in the U.S. The life cycle and source of S. canis are unknown. The present report of S. canis-like infection in a sea mammal from Spain indicates that the definitive host for this parasite also exists outside of U.S.