Chimeric recombinant protein (rErpY-LemA) as innovative tools for animal leptospirosis serodiagnosis.

Leptospirosis is a zoonosis with widespread worldwide. Transmission occurs through direct or indirect contact with contaminated water, urine, milk, and soil. Symptoms are variable but can lead to significant losses for producers, making it a major economic concern in livestock farming. The Microscopic Agglutination Test (MAT) is the gold standard for leptospirosis diagnosis but presents limitations, such as the need for live Leptospira cultures, specialized infrastructure, and trained personnel. It is time-consuming, labor-intensive, and poses health risks due to live pathogen handling. Simpler, safer alternatives, such as the Enzyme-Linked Immunosorbent Assay (ELISA) using recombinant antigens, are needed. In this study, we developed an ELISA using a recombinant chimera, rErpY-LemA, which combines the ErpY-like and LemA Leptospira proteins as an antigen. The chimera was tested with sera from various Leptospira serovars and showed significant reactions (P < 0.001) with antibodies against 12 strains. The chimera showed promising diagnostic performance in cattle (n = 335) and sheep (n = 259) sera, confirmed by MAT. The AUC was 0.903 for bovine (sensitivity: 98.3-100 %, specificity: 60.9-78.2 %) and 0.917 for ovine (sensitivity: 97.7-100 %, specificity: 57.1-76.5 %). The test showed strong agreement with MAT, with a PPV of 81.3 %-90.2 % for cattle and 77.4 %-88.4 % for sheep. These results confirm that rErpY-LemA is an effective antigen for diagnosing leptospirosis in cattle and sheep, being able to detect different serovars. Thus, ELISA using the rErpY-LemA chimera is a promising tool for leptospirosis screening in livestock, offering a safer and more practical alternative to MAT.