Comparative cervical skin tuberculin test responses

Infection status (no. of cattle)Mean ± SE change in skin thickness (mm)aStatusb
M. avium PPDM. bovis PPD
Noninfected (5)1.5 ± 0.53 A0.5 ± 0.15 AAll negative
M. kansasii infected (4)5.4 ± 0.52 B4.6 ± 0.28 BAll negative
M. bovis infected (9)4.3 ± 0.5 B26.3 ± 3.65 CAll reactors
  • a Animals received 0.1 ml (100 μg) of M. bovis PPD and 0.1 ml (40 μg) of M. avium PPD in the midcervical region according to guidelines described in USDA, APHIS circular 91-45-01 (39a). Skin thickness changes (mm) in response to PPD stimulation (mycobacterial origin indicated) are presented as the means ± standard errors at 72 h after injection minus the skin thickness prior to injection. The letters A through C indicate responses that differ (P < 0.01) for a specific stimulation (i.e., vertical comparisons). The same letter indicates that the responses did not differ.

  • b Change in skin thickness values for individual animals were plotted on a scattergram for the interpretation of CCT results (USDA, APHIS, Veterinary Services form 6-22D, cattle bison interpretation [39b]) and characterized as negative or suspect for TB or reactive to tuberculosis exposure.