Development and validation of an ELISA test for the diagnosis of bovine Leptospirosis

Abstract

Leptospirosis is a worldwide zoonotic disease that affects most domestic and wild animals as well as man. In cattle, leptospirosis causes agalactiae, abortion and other reproductive disorders. The diagnosis is based primarily on serology. The international reference serologic test, the Microscopic Agglutination Test (MAT), is the most commonly used.

An enzyme-linked inmunosorbent assay (ELISA) for detecting IgG anti-Leptospira antibodies in bovine serum was developed and validated with the MAT.

Sonicated antigen from cultures of serovar hardjo (strain Hardjoprajitno) was used for the ELISA. Strains of 8 serovars of Leptospira interrogans were used for the MAT. Serum samples from 535 bovine, 356 MAT positive and 179 MAT negative, were evaluated. At the optimal cut-off point recommended by receiver operating characteristic (ROC) curve analysis, the sensitivity and specificity values of the ELISA were 99.4% (95% CI= 98.0-99.9) and 96.1% (95% CI= 92.1-98.4) respectively. Concordance between ELISA and MAT measured by Kappa (k), was 0.96 (p< 0.001). The value for the area under this ROC curve was 0.995 (CI 95% =0.984-0,999), indicating a high level of accuracy for this ELISA. In comparison with serovar-specific assay this assay could detect Leptospira-infection by using only one test, specially in areas where the prevalent serovars are unknown. This assay has several advantages: it uses non hazardous reagents, it is repeatable, it is scored objectively and easy to perform in non specialized laboratories. In conclusion, this genus-specific IgG ELISA may constitute a very useful tool for the diagnosis of leptospiral infection in cattle.