Babesia bigemina: immune response of cattle inoculated with irradiated parasites.

Bisuiop, J. P., Am) Ai)sis, L. G. 197-1. Babesia bigernina: hlinnne response of cattle inoculated with irradiated parasites. Experimental Parasitology 35, 35-43. Effects of various radiation dosages on the infectivity and immunogenicity of Babesia blgerninawere studied. Calves infected with 1 x 10"' B. higeinina parasitized erytliro­ cytes exposed to 24 krad developed progressive parasitenias. Some calves receiving 1 X 10"' parasitized erythrocytes irradiated at 36 krad did not develop progressive infections. Progressive infections were prevented hy exposure to irradiation at -18 and 60 krad. A degree of acquired resistance to infection with B. bigeytina developed in calves after inoculation with parasites irradiated at -18 and 60 krad. The resistance developed was sufficient to suppress multiplication of the Babesia and to permit calves to survive otherwise severe clinical infections due to challenge with nonirradiated parasites. Irradiated parasites were frozen without apparent loss of inmunizing properties.