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

The research article explored the use of schizont and piroplasm antigens of Babesia equi in serological tests, namely the indirect fluorescent antibody test (IFAT) and the complement fixation test (CFT), on eight infected ponies. Significant differences were found in the ability of these tests to detect and measure antibodies to the two antigens, especially in terms of duration post infection.

Background and Purpose

• The study was conducted to examine the use of two types of antigens of Babesia equi, a parasitic organism that causes disease in horses, in two serological tests – the indirect fluorescent antibody test (IFAT) and the complement fixation test (CFT).
• The antigens used were schizont and piroplasm, parts of the life stage of the parasite. Schizont antigen was produced from cultured lymphoid cells that contained B. equi macroschizonts, while piroplasm antigen was prepared from an infected, splenectomized pony.
• These serological tests were utilized to track and quantify the antibody response in infected ponies.

Methodology and Findings

• The eight ponies infected with Babesia equi were examined using both IFAT and CFT. The researchers tracked changes in antibody titres, or concentrations, towards both schizont and piroplasm antigens.
• Both tests were capable of detecting an increase in antibody concentrations to schizont and piroplasm antigens. However, the duration of antibody detection varied between the two antigens.
• Antibodies to piroplasm antigen were found to be detectable for a longer period after infection compared to schizont antigen. This indicates that the immune response against piroplasm antigens persists longer than it does against schizont antigens post-infection.

Effectiveness of Tests

• The complement fixation test, unlike the IFAT, was not effective in detecting specific antibodies to schizont antigen. Antibody titres to schizont were generally low and were undetectable in three of the horses.
• Moreover, no serological cross-reaction was observed with the antigens of B. caballi and B. bigemina, two other species of Babesia, when using schizont antigen. This suggests that the immune response to B. equi is specific and does not cross-react with antigens from other Babesia species.