CONICET | Buscador de Institutos y Recursos Humanos

Cattle (Bos taurus) are intermediate hosts for three named species of Sarcocystis, S. cruzi, S. hirsuta, and S. hominis. Recently, a fourth species was identified and named S. sinensis. However, S. sinensis originally named a species of Sarcocystis in water buffalo (Bubalus bubalis) in China. Based on unverifiable evidence, it was suggested that the same parasite infects cattle. In addition,S. sinensis was recently declared as nomen nudum because its namingviolated the rules of International Code of Zoological Nomenclature. Thus, thefourth species using cattle as an intermediate host does not have a validname. Here, we propose a new name, Sarcocystis rommeli for the S. sinensis-likeparasite from cattle in Argentina, and differentiate it ultrastructurallyfrom S. hominis sarcocysts from experimentally infected cattle. Sarcocystisrommeli sarcocysts were microscopic with a 5-lm-thick wall with slender villarprotrusions (Vp); the Vp were up to 5 lm long, up to 0.5 lm wide, and ofuneven thickness, often bent at an angle. The ground substance layer (Gs)was up to 0.8 lm thick and smooth. Vesicular structures were seen at thebase of the Vp. The bradyzoites were 10?12 lm long. Sarcocystis hominis sarcocysts had Vp that were often upright, up to 7.5 lm long, and up to 1.8 lmwide; the Gs was up to 2 lm thick and without vesicles. Its sarcocyst wallwas up to 5.6 lm thick, the vp were bent at an angle, up to 5.8 lm long, theGs was up to 2 lm thick, but without vesicles seen in S. rommeli. Beef containing sarcocysts of S. rommeli was not orally infectious for two human volunteers and a red fox (Vulpes vulpes). The Sarcocystis described here ismolecularly different from S. cruzi, S. hirsuta, and S. hominis based on 18SrRNA and cox1 gene sequences

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