Redescription, deposition of life-cycle stage specimens of <i>Sarcocystis bovifelis</i> Heydorn, Gestrich, Mehlhorn and Rommel, 1975, and amendment to <i>Sarcocystis hirsuta</i> Moulé, 1888.

There is considerable debate concerning the life cycles and taxonomy of <i>Sarcocystis</i> species in cattle. Of the 8 species of <i>Sarcocystis</i> named from cattle, 2 (<i>Sarcocystis cruzi</i> and <i>Sarcocystis heydorni</i>) are morphologically distinctive because their sarcocysts are microscopic and the sarcocyst wall is thin (&lt;0.5 <i>μ</i>m thick). The sarcocysts of the remaining species (<i>Sarcocystis hirsuta</i>, <i>Sarcocystis hominis</i>, <i>Sarcocystis bovini</i>, <i>Sarcocystis bovifelis</i>, <i>Sarcocystis sinensis</i>, <i>Sarcocystis rommeli</i>) have thick (5–8 <i>μ</i>m) walls indistinguishable by light microscopy, alone. To provide needed clarity, I herein review the history, nomenclature and life cycle of <i>S. bovifelis</i> (originally named by Heydorn and associates from Germany), redescribe it and deposit specimens of its various life-cycle stages at a museum for future reference. I also provide means to distinguish this parasite from <i>S. hirsuta</i>. Cats are the definitive hosts for both <i>S. bovifelis</i> and <i>S. hirsuta</i>. The sarcocysts of <i>S. bovifelis</i> are microscopic, its sarcocyst wall is type 10g, it has 2 schizogonic stages in blood vessels and sarcocysts are formed between 25 and 30 days post-inoculation in striated muscles, but not in the heart. Sporulated oocysts are 17.1 × 12.7 <i>μ</i>m and sporocysts are 12.8 × 8.4 <i>μ</i>m. The sarcocysts of <i>Sarcocystis hirsuta</i> are macroscopic, up to 7 mm long, its wall is type 18. Nothing is known of the development of <i>S. hirsuta</i> in cattle tissues and in cat intestine. Size of its oocysts and sporocysts is uncertain.