Serodiagnosis of Babesia equi infection--a comparison of Dot-ELISA, complement fixation test and capillary tube agglutination test.

The present study aimed to develop Dot-ELISA, complement fixation test (CFT) and capillary tube agglutination test (CAT) for serodiagnosis of Babesia equi infection and to compare their sensitivity with each other. For this study, sequential serum samples were collected from four donkeys experimentally infected with B. equi up to 90 days post infection (P.I.). B. equi antigen was prepared from the blood of a donkey showing more than 80% parasitaemia. Dot-ELISA, CF and CA tests were standardized as per the standard method. While performing CFT, it was observed that CFT standardized for the donkey system could not be applied to the horse system, and different units of the same antigen and complement were required for each. Dot-ELISA detected antibodies from 3-6 days P.I. onwards, whereas CF and CA tests could detect antibodies from the 6th day P.I. indicating that Dot-ELISA is the more sensitive. The efficacy of these three tests was also determined by testing 211 field serum samples of apparently healthy horses. By Dot-ELISA 49.76%, by CAT 42.18% and by CFT 27.86% of the serum samples were found positive. As the results of Dot-ELISA and CAT are comparable, it is proposed that CAT may be used as a screening test.