Comparison of ante-mortem assays to assess progression/regression of paratuberculosis in individual dairy animals.

Johne's disease, caused by Mycobacterium avium, subspecies paratuberculosis (MAP) is becoming increasingly widespread on dairy farms worldwide, due in part, to the absence of vaccine/drug or curative modalities.  This spread is of concern since MAP is at the center of a controversy as to its role in Crohn's disease.  None of the methods presently available to define paratuberculosis in cattle have been examined for their ability to assess progression/regression of any treatment or intervention of this disease   The research presented herein, therefore was designed to assess the reliability and accuracy of available ante-mortem assays to predict disease change of individual animals undergoing a probiotic, potentially therapeutic, treatment.  Paratuberculosis positive (n = 75) and negative (n = 10) animals were longitudinally monitored over their natural lifetimes with specific serum antibody and fecal shedding assays, and for development of end-stage clinical disease.  Longitudinal, increasing/decreasing serum ELISA values were associated with, and predictive of, progression/regression of disease.  Changes in fecal shedding and serum AGID were of value at only specific stages.  Documentation that ELISA-positive animals were positive for paratuberculosis was done by a compilation of ELISA-independent assays--succumbing with end-stage clinical disease, autopsy, AGID, and MAP fecal shedding.