Detection of antibodies against Anaplasma marginale in milk using a recombinant MSP5 indirect ELISA

At a cutoff of 42 PP, the ELISA has 98% sensitivity and 95% specificity. A significant difference (P < 0.0001) was found between the mean PP value of negative samples from G1 (17.4 ± 14.9), and G2 (8.6 ± 7.1). The agreement and kappa (κ) value between iELISA and PCR was 96%, κ = 0.919; between iELISA and CAT was 97%, κ = 0.880; and between iELISA and cELISA was 97%, κ = 0.899. These results strongly support the usefulness of iELISA to detect A. marginale antibodies in milk. Additional studies are necessary to define the ability of the milk iELISA to detect not only acutely infected, but also carrier cattle.