Fig 5.

Skin test specificities of PPDB, PPDA, and the protein cocktail in TB-free herds. Two groups of animals from farms with no history of tuberculosis were tested. One farm had M. avium subsp. paratuberculosis infection. The responses for individual animals are represented by black dots, and the lines show the means and interquartile ranges, with the results expressed as the difference in skin thicknesses between post- and pre-skin test readings. The statistical differences between responses were determined by using the Kruskal-Wallis test (**, P < 0.01; ***, P < 0.001).