Acta Parasitologica, Vol. 52, No. 4, 2007,
299–304.
DOI: 10.2478/s11686-007-0048-6
J. P. Dubey (1)*, Benjamin M. Rosenthal (1), Natarajan Sundar (1), G.V. Velmurugan (1) and Kimberlee B. Beckmen (2)
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Sarcocystis arctosi sp. nov. (Apicomplexa, 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 (Ursus maritimus)
(1) Animal Parasitic Diseases Laboratory, United States Department of Agriculture, Agricultural Research Service, Animal and Natural Resources Institute, BARC-East, Building 1001, 10300 Baltimore Avenue, Beltsville, MD 20705-2350, USA; (2) Division of Wildlife Conservation, Alaska Department of Fish and Game1300 College Road, Fairbanks, AK 99701-1599, USA
*Corresponding author:
jitender.dubey@anri.barc.usda.gov
ABSTRACT
The tissues of herbivores are commonly infected with cysts of parasites belonging to the apicomplexan genus
Sarcocystis, but such sarcocysts are rare in bears. Here, we describe a new species, Sarcocystis arctosi,
based on the mature sarcocysts identified in two brown bears (Ursus maritimus) from Alaska, USA. Microscopic sarcocysts
(37–75 × 20–42 µm) had thin walls (<1 µm). The outer layer of the sarcocyst, the parasitophorous vacuolar membrane (pvm),
was wavy in outline and had minute undulations that did not invaginate towards the sarcocyst interior; these undulations
occurred at irregular intervals and measured up to 100 nm in length and up to 60 nm width. The ground substance layer beneath the pvm
was smooth and lacked microtubules. Longitudinally cut bradyzoites measured 5.6–6.8 × 0.7–1.8 µm. A major portion of nuclear small
subunit rDNA sequence obtained from these sarcocysts was similar to that previously obtained from the hepatic schizonts of a S. canis-like parasite from polar bears (Ursus maritimus).
KEY WORDS:
Protozoa, Apicomplexa, Sarcocystis arctosi sp. nov., brown bear, Ursus arctos