Continuous in vitro cultivation of Babesia gibsoni

Two stocks of the protozoan parasite Babesia gibsoni, one of the causative agents of canine piroplasmosis, were propagated continuously in dog erythrocytes in microaerophilous stationary-phase culture. Cultures of both stocks were initiated in a humidified 5% CO2, 2% O2, 93% N2 atmosphere at 37 degrees C at a time when very few parasites (<0.01%) were detected in a thin blood smear. Cultures of one stock were also initiated in a humidified atmosphere of 5% CO2 in air at 37 degrees C during a patent parasitaemia (2.6%) in the donor animal. The culture medium was a modified HL-1 medium supplemented with dog serum, L-glutamine and antibiotics. Culture-derived parasites were cryopreserved and resuscitated. Cultures of each stock were propagated for 102 days and 51 days, respectively, before they were terminated.