Purification of the erythrocytic stages of Babesia bigemina from cultures.

Exposure of erythrocytes infected with Babesia bigemina to glycerol-enhanced osmotic shock yielded preparations containing infected erythrocyte ghosts, free parasites, and some intact erythrocytes. The released parasites were purified and concentrated by centrifugation in Percoll gradient. Recovered free parasites were shown by the fluorescein acetate technique to be metabolically active, but their infectivity in vitro was low. It was demonstrated by electron microscopy that most of the released parasites had intact plasma membranes. There was only slight contamination of the free-parasite preparation with host erythrocyte debris.