Continuous in vitro cultivation of Babesia caballi in serum-free medium.

Experiments were undertaken to develop a serum-free medium for the in vitro cultivation of Babesia caballi, a tick-borne hemoprotozoan parasite, one of the causative agents of equine piroplasmosis. A modified HL-1 medium supplemented with horse serum, L-glutamine, antibiotics, and hypoxanthine was used. B. caballi organisms were continuously cultivated at 37 degrees C in microaerophilous stationary-phase culture in a humidified atmosphere containing 5% CO2 in air before exposure to serum-free culture conditions. For serum-free propagation, lipid-rich bovine serum albumin (LR-BSA), alone or with chemically defined lipids (CDL), were added instead of serum. Media containing LR-BSA alone or LR-BSA and CDL in various amounts supported the in vitro propagation of B. caballi. Growth was maintained for more than 6 months. The growth rates obtained in serum-free media were similar to those previously obtained in traditional serum-containing medium.

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.