Use of schizont and piroplasm antigens of Babesia equi in the indirect fluorescent antibody and complement fixation tests.

Eight ponies infected with Babesia equi were investigated for their serological response to B. equi schizont and piroplasm antigen with the indirect fluorescent antibody test (IFAT) and complement fixation test (CFT). Piroplasm antigen was prepared from an infected splenectomized pony, while schizont antigen was produced from cultured lymphoid cells which contained B. equi macroschizonts. The IFAT detected a rise in antibody titres to schizont antigen as well as to piroplasm antigen, but differences were obtained in the duration of antibody detection. Significant antibody titres to piroplasm antigen were detectable for a longer period post infection than to schizont antigen. The complement fixation test was not effective in detecting specific antibodies to schizont antigen in contrast to piroplasm antigen. The schizont antibody titres were in general extremely low and not detectable in 3 horses. Neither test showed any serological cross-reaction with B. caballi and B. bigemina antiserum using schizont antigen.