Improved in vitro cultivation of Babesia caballi

Babesia caballi infected erythrocytes were collected from the blood of an experimentally infected horse and could be continuously cultivated in vitro with parasitemia ranging from 2-4% in RPMI 1640 medium supplemented with 2 mM L-glutamine, 20 mM HEPES and 40% adult horse serum in a low oxygen atmosphere (2% O2, 5% CO2 and 93% N2). All attempts to increase parasitemia failed using other culture media, serum concentrations and culture vessels. However, parasite growth was enhanced by transfer of cultures from a low oxygen to 5% CO2 in air, with parasitemia ranging from 8-10%.