Diagnosis of Babesia caballi infections in horses by enzyme-linked immunosorbent assay (ELISA) and western blot.

This research focuses on how the ELISA and Western blot diagnostic methods can effectively detect Babesia caballi infections in horses. These methods are compared with other tests, proving that the ELISA, with its 98.3% sensitivity, is superior, making it the best diagnostic tool for identifying carrier horses and preventing the spread of infection.

Methodology of the Research

• The research began by obtaining a preparation of host cells – infected erythrocytes, 100% infected with Babesia caballi, from in vitro cultures.
• The B. caballi antigens were then extracted from these infected cells using the detergent 3-[(3-Cholamidopropyl)-dimethylammonio]-1-propane-sulfonate (CHAPS), which served as the ELISA antigens.
• The team established a control group by preparing a similar antigen derived from normal erythrocytes from the same horse donor.
• Testing began by validating the ELISA and Western blot using the sera of horses that were either infected with B. caballi or B. equi, or not infected with Babesia spp.

Comparison of Testing Methods

• The results from the ELISA and Western blot tests were compared with the immunofluorescence antibody test (IFAT) and complement fixation test (CFT).
• The ELISA demonstrated a 98.3% sensitivity to detecting B. caballi antibodies from the 14th day following infection, outperforming both the Western blot (94.9%) and the IFAT (96.6%). The CFT demonstrated the least sensitivity, at 28.8%.
• The tests also demonstrated 100% specificity, with no positive results from the ELISA and Western blot when testing 106 sera from horses not infected with Babesia spp.

Consideration of Cross Reactions

• The researchers found that B. equi-positive sera elicited more cross reactions in the ELISA (20%) than in the IFAT (4%).
• No cross reactions were reported with the Western blot and the CFT.

Conclusion and Implications of the Research

• Further validity of the ELISA’s higher sensitivity was shown when testing 132 field sera – the ELISA detected more positive results (112) compared to the IFAT (92) and CFT (41).
• Thus, the researchers concluded that ELISA, being the most sensitive test, provides the best method for identifying carrier horses.
• This highlights its crucial role in preventing the introduction and spread of Babesia caballi infections into non-endemic areas, which is significant for exporting testing and the larger equine health community.