Extraction and preliminary use for diagnosis of soluble precipitating antigen from Babesia bigemina.

Soluble antigen from bovine blood with a Babesia bigemina parasitemia of 5-6% formed 4 precipitin lines in gel diffusion tests with antiserum from infected cattle. Antigen was obtained from plasma and hemolysate by elution from DEAE cellulose columns and (NH4)2SO4 precipitation as well as from washed parasite-erythrocyte stroma by sonication or freeze-thawing. About 5 ml of antigen suitable for diagnostic tests could be extracted from 200 ml of infected blood.