Advances in ELISA-based detection of equine leptospirosis.

Leptospirosis is a globally distributed zoonosis that affects both humans and animals, with Leptospira interrogans being the main causative agent. In horses, the disease is associated with considerable economic losses. The Microscopic Agglutination Test (MAT) is the reference test for diagnosis but has limitations, emphasizing the need for effective diagnostic alternatives. In this study, was evaluated the use of a recombinant chimera, composed of ErpY-like and LemA proteins, as an antigen for ELISA-based detection of equine leptospirosis. The chimera was successfully expressed, purified and tested on 915 horse serum samples previously analyzed by MAT. The ELISA correctly identified all positive samples, with no false negative observed. The ROC curve analysis, considering different hypothetical prevalence values, reached up to 0.92. The assay demonstrated sensitivity ranging from 98.8% to 100%, specificity from 77.6% to 84%, positive predictive value between 68.6% and 77.2%, and negative predictive value between 92% and 100%. The Kappa coefficient was 0.7432, indicating good agreement with MAT. When samples were categorized by titers, those with a 1:400 dilution achieved the highest accuracy (99%), while those with a 1:100 dilution showed slightly lower accuracy (94.8%), demonstrating that higher antibody titers resulted in a more effective assay. The major serovars that cause infection in horses, such as Bratislava, Icterohaemorrhagiae, Sejroe, Pomona, and Copenhageni, react with rErpY-lemA. These results suggest that the ErpY-LemA chimera is a promising screening tool for equine leptospirosis, offering a valuable alternative for the rapid and accurate detection of different serovars and titers.