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 erythro cytes in microaerophilous stationary-phase culture. Cultures of both stocks were initiated in a humidified 5% CO2, 2% O-2, 93% N-2 atmosphere at 37 de greesC at a time when very few parasites (<0.01%) were detected in a thin b lood smear. Cultures of one stock were also initiated in a humidified atmos phere 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 supplem ented with dog serum, L-glutamine and antibiotics. Culture-derived parasite s were cryopreserved and resuscitated. Cultures of each stock were propagat ed for 102 days and 51 days, respectively, before they were terminated.