In vitro cultivation of Babesia occultans.

Babesia occultans, the causative agent of a benign form of cattle babesiosis in South Africa, was continuously cultivated in microaerophilous stationary-phase culture. A modified medium, 199, supplemented with either 40% (v/v) bovine or 40% (v/v) horse serum, was used. Cultures were initiated in a humidified atmosphere containing 2% O2, 5% CO2, and 93% N2. The highest percentage of parasitized erythrocytes (PPE) reached 4.5% in horse-serum- and 2.4% in bovine-serum-supplemented medium. Parasite suspensions were cryopreserved and successfully resuscitated.