Evaluation of the 48 hour, 72 hour and 96 hour readings of tuberculin test for the screening of tuberculosis in cattle

In this study, a cattle farm with a history of tuberculosis was examined over a period of three years to determine the usefulness of reading tuberculin tests (single intradermal cervical tuberculin test (SICTT) and single intradermal comparative cervical tuberculin test (SICCTT)) at 48 hrs, 72 hrs and 96 hrs intervals in the diagnosis of tuberculosis. On the onset, SICTT was conducted on a total of 145 cattle, 52 (35.9%) of these were positive at 48 hours, 56 (38.6%) at 72 hours and 65 (44.8%) at 96 hours (X2=1.54, p=0.46). After one year, 171 cattle were screened using SICCTT, 10 (5.8%) animals were positive at 48 hours, 12 (7.0%) at 72 hours and 14 (8.2%) at 96 hours (X2=0.67, p=0.72). During the third test conducted almost one year after the second test, 136 cattle were screened using SICCTT, 13 (9.6%) were positive at 48 hours, 17 (12.5%) at 72 hours and 17 (12.5%) at 96 hours (X2 = 0.68, p=0.71). With the pattern of this result, there may be need to review the policy which gave the 72 hr reading a preference over the 96 hr reading of tuberculin test. African Journal of Clinical and Experimental Microbiology Vol. 6 (3) 2005: 223-226