The effects of irradiation on Babesia maintained in vitro.

Blood infected with Babesia radhaini, B major or B divergens was irradiated to different absorbed doses between 0 and 120 krad, and then maintained in vitro in the presence of 3H hypoxanthine for 24 h. The effects of irradiation were measured by the ability of the parasites to incorporate 3h hypoxanthine and, in the case of B rodhaini, by the ability of the parasites to infect mice. B major and B divergens were slightly more radio-resistant than B rodhaini, but all showed a progressive fall in ability to incorporate 3H hypoxanthine with increasing doses of irradiation, except at low doses of irradiation when there was increased uptake of 3H hypoxanthine. In the case of B rodhaini there was close correlation between the ability of the parasites to incorporate 3H hypoxanthine and their infectivity for mice. Both types of activity were abolished at doses of 40 krad and above.