The serological response of calves to Leptospira interrogans serovar hardjo vaccines and infection as measured by the microscopic agglutination test and anti-IgM and anti-IgG enzyme-linked immunosorbent assay.

The microscopic agglutination test (MAT) and the anti-IgM and anti-IgG enzyme-linked immunosorbent assays (ELISA) were used to examine sera taken over the course of 16 weeks from 35 calves vaccinated and/or infected with Leptospira interrogans serovar hardjo. The relationship between the IgM and IgG responses to vaccination and infection were determined. The rapid and high rise in IgM levels following challenge made the anti-IgM ELISA a potentially good indicator of recently established infection although some transitory high levels were seen where infection did not become established. The slow IgG response to infection made the anti-IgG ELISA of limited diagnostic use.