Electron microscope study of merogony preceding cyst formation of Sarcocystis sp. in roe deer (Capreolus capreolus)

Precystic merogony of Sarcocystis sp. was studied in roe deer fawns 33, 45, and 49 days postinoculation (pi) with 2 X 10(4)-10(5) sporocysts recovered from dogs. Single merozoites, but no meronts, were found 33 days pi in liver, spleen, and lymph nodes. Transforming merozoites and meronts were found in myofibroblasts, satellite cells, and endothelial cells of muscle tissue on 45 and 49 days pi; they were surrounded by two membranes. Typical coccidian merozoites differentiated simultaneously around an enlarged, lobed nucleus.