Abstract
Cattle (Bos taurus) are intermediate hosts for four species of Sarcocystis, namely Sarcocystis cruzi, Sarcocystis hirsuta, Sarcocystis hominis, and Sarcocystis rommeli. Of these four species, mature sarcocysts of S. cruzi are thin-walled (<1μm), whereas S. hirsuta, S. hominis, and S. rommeli have thick walls (4μm or more). Here, we describe a new species of Sarcocystis with thin-walled sarcocysts in cattle. Two newborn calves were fed with sporocysts from the feces of a human volunteer who had ingested raw beef. The calves were killed 111 and 222days later. In addition to thick-walled sarcocysts of S. hominis, both calves were coinfected with a Sarcocystis species that had a thin-walled sarcocysts, distinct from S. cruzi. The sarcocysts were mature, microscopic, up to 80μm wide, and up to 1060μm long. By light microscopy, the sarcocyst wall was thin (<1μm thick) and had minute protrusions. By transmission electron microscopy, the sarcocyst wall had short, conical villar protrusions (vp) that were up to 0.5μm long and up to 0.5μm wide, similar to type 29. The vp on the sarcocyst wall lacked microtubules but had six or more disc-shaped plaques. The ground substance layer was smooth, approximately 0.5μm thick, and without microtubules. The bradyzoites were 8-11μm long. The structure of the sarcocyst wall was distinct from any species of Sarcocystis reported from livestock. This unique species is named in honor of Dr. Alfred Otto Heydorn who provided the sporocysts.
Published Version
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