Fig. 2

Test value of the skin test for M. bovis infected and uninfected warthogs. Test value was calculated by subtracting the PPD_a injection sites’ skin fold thickness from that of the PPD_b injection site after 72 h (PPD_b - PPD_a). Median and interquartile ranges are represented by the horizontal bars. The dotted lines represent the various published cut-off values in other species (1, 2 and 4 mm). *** indicates p < 0.001