Comparison of fluorescence polarization assay and enzyme-linked immunosorbent assay for the diagnosis of bovine paratuberculosis

Mycobacterium avium subspecies paratuberculosis (Map), is the etiological agent of paratuberculosis, a disease that affects cattle and causes economic losses to the animal husbandry industry. Its opportune diagnosis, in herds, is part of the control measures of the disease; therefore, the objective of this work was to compare paratuberculosis detection of infected bovines with the Fluorescence Polarization Assay (FPA) and Enzyme-linked Immunosorbent Assay (ELISA). Six-hundred and three sera and feces samples, from bovines older than 2 years old were studied. The sera were assessed with the FPA technique using as antigen a protein fraction of 35 kDa obtained from the raw extract of the Map strain 3065, and for ELISA the protoplasmic antigen of the same strain was used. DNA was obtained from the feces and assessed by nested PCR. The correlation of results was established by Kappa Test.  The FPA test had sensitivity (Se) of 88.50% and specificity (Sp) of 91.42% (p ≤0.000); for ELISA Se 83.86% and Sp 89.87% (p ≤0.000) were obtained. Concordance (K) between tests was 0.6742%, and when compared with nested polymerase chain reaction (PCR), the FPA test had K = 0.7314%, while for ELISA it was 0.5771%. The FPA technique using as antigen the protein fraction of 35 kDa showed a higher sensitivity and specificity, moreover it was a simple technique for the determination of the antigen-antibody interaction, and therefore it becomes an alternative diagnostic tool to detect paratuberculosis infected bovines. Key words: Paratuberculosis, diagnosis, fluorescence polarization assay (FPA), enzime-linked immunoabsorbent assay (ELISA).