Comparison of three serological tests and an interferon-gamma assay for the diagnosis of paratuberculosis in experimentally infected sheep

Objective To compare the diagnostic performance of a complement fixation te st, an agar gel immunodiffusion test, an enzyme-linked immunosorbent assay, and a whole-blood interferon-gamma assay for paratuberculosis in 14 sheep experimentally infected with Mycobacterium avium subsp paratuberculosis. Experimental design Longitudinal study. Results The IFN-gamma assay detected more experimentally infected sheep, an d earlier, than any of the serological tests. None of the antibody assays w as able to detect all sheep with histologically confirmed paratuberculosis. Conclusions The superior performance of the IFN-gamma assay in detecting in fected sheep in this small experimental population warrants its further eva luation in a larger population of sheep naturally exposed to M a paratuberc ulosis.