Morphologic Development of an Unidentified Species of Sarcocystis Associated with Encephalitis in a Gray Fox (Urocyon cinereoargenteus)

Morphologic development of unidentified Sarcocystis sp. schizonts associated with encephalitis in a 9-wk-old gray fox (Urocyon cinereoargenteus) from Texas is described. Sarcocystis schizonts were confined to lesions. They were sparsely distributed and their staining affinity for hematoxylin and eosin varied with developmental stages; immature schizonts were deeply stained compared with mature schizonts. Most parasites were extravascular and the host cell was not identified for those that were intracellular. The parasite divided by endopolygeny, in which the nucleus became lobulated but lobes remained connected. Schizonts were up to 30 μm long and contained up to 32 merozoites/nucleus. The merozoites were slender and unlike any known species of Sarcocystis. The schizonts were distinct from Sarcocystis neurona schizonts, which cause encephalitis in many species of animals.