Submitted to: Acta Parasitologica
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/1/2007
Publication Date: 12/5/2007
Citation: Dubey, J.P., Rosenthal, B.M., Sundar, N., Velmurugan, G.V., Beckman, K.B. 2007. Sarcocystis arctosi, n. sp. (Apicomplexans: Sarcocystidae) from the brown bear (Ursus arctos), and its genetic similarity to schizonts of Sarcocystis canis-like parasite associated with fatal hepatitis in polar bears. Acta Parasitologica. 52:299-304. Interpretive Summary: Sarcocystis species are single celled parasites that cause illness in humans and livestock. Humans can become infected with this parasite by ingesting infected pork and beef. Cattle and pigs can become infected by ingesting food and water contaminated with the resistant parasite stages excreted in feces of infected humans.Many species of Sacrcocystis are pathogenic to animals. Scientists at the Beltsville Agricultural Research Center and Department of Wildlifre Alaska report on a previously unrecognized species os Sarcocystis in grizzly bears.The results will be of interest to biologists, parasitologists, public health workers,and veterinarians.
Technical Abstract: Although all species of Sarcocystis are presumed to cycle between carnivorous definitive hosts and their prey, complete life-cycles have been definitively established for only a few. Instead, most such species are known only by the sarcocysts that form in intermediate hosts, which may be discriminated on the basis of ultrastructural characteristics. Rarely, experimental infections in captive carnivores have enabled completion of the life-cycle of such parasites, and molecular epidemiology has occasionally elucidated connections among disparate natural infections. Here, we describe a new species, Sarcocystis arctosi, based on the mature sarcocysts identified in each of two grizzly bears (Ursus arctos) from Alaska, USA, and report their unexpected genetic resemblance to schizonts previously reported as responsible for hepatic illness in a polar bear. Surprisingly, no differences were evident when comparing a major portion of nuclear small subunit rDNA sequence obtained from these sarcocysts with that previously obtained from the schizonts of S. canis. Future study should seek to definitvely establish whether or not the schizonts of Sarcocystis canis and the sarcocysts of S. arctosi and represent distinct life-history stages of the same etiological agent, in which case former name would have priority. Coupling detailed parasite descriptions with a comparative genetic framework provides a unique means by which to connect otherwise disparate observations.