Countercurrent immunoelectrophoresis, a technique for the diagnosis of bovine babesiosis.

The countercurrent immunoelectrophoresis (CIE) test was performed as a diagnostic tool for bovine babesiosis using a partially purified soluble antigen obtained from a saline extract of B. bovis-infected bovine erythrocytes by 60% ammonium sulphate precipitation (Bb-ag), and it was compared with the indirect fluorescent antibody test (IFA). Antibodies against B. bovis were detected in all 3 experimentally infected calves at the 8th post-infection day by IFA while antibodies to Bb-ag at the 10th postinfection day by CIE. These antibodies persisted until the end of the observation period (90th day post-infection). 43 serum samples from 116 bovines coming from a Babesia-enzootic area were positive (antibody titers > 1:30) by IFA test. 36 from the 43 (94%) IFA -positive bovine serum samples had antibodies to B. bovis soluble antigen (Bb-ag) detected by CIE. In contrast, the 20 serum samples from a Babesia-free area were all negative by both these methods. No cross-reactivity was observed with the soluble antigen obtained from normal red blood cells in the 3 experimentally infected calves nor in the bovines coming from a Babesia-enzootic area. CIE employing Bb-ag was as specific as IFA test but slightly less sensitive (100 vs. 94%) and detected antibodies to B.bovis early during the infection (8 vs. 10 days post-infection). Since CIE is easy to perform, does not require expensive reagents, material or equipment, and one can analyze up to 50 serum samples at once in a short time it is recommended as a useful test for the diagnosis of bovine babesiosis in developing countries.