Intraerythrocytic multiplication of Theileria parva in vitro: An ultrastructural study

Intraerythrocytic multiplication of Theileria parva in vitro: an ultrastructural study. International Journal for Parasitology 16: 223-229. Piroplasms of a Theileria parva isolate from Muguga, Kenya were maintained in short-term stationary erythrocyte cultures and the mode of multiplication studied by light and electron microscopy. Division of single piroplasms into four intraerythrocytic merozoites was observed within the first 24 h in vitro. After 8 days of cultivation, 10-20% of the parasitised erythrocytes contained quadruplet merozoite forms resulting from multiplication in vitro. Electronmicrographs showed that intraerythrocytic multiplication occurred by a schizogonous process that proceeded from the initial formation of rhoptries and electron-dense cytoplasmic plaques beneath the parasite's plasmalemmal membrane, to nuclear division and the final separation of a maximum of four differentiated merozoites. The merozoites formed by intra-erythrocytic schizogony in vitro had ultrastructural features identical to merozoites produced by intra-lymphocytic schizonts of T. parva.