COMPARISON OF THE EFFICIENCY OF 4 DOSES OF BOVINE PPD TUBERCULIN IN CATTLE AND GUINEA-PIGS - RECOMMENDATIONS FOR THE MOST SUITABLE DOSE FOR USE IN THE SINGLE CAUDAL FOLD TEST IN CATTLE

The potencies of 4 batches of Australian bovine PPD tuberculin relative to the standard British bovine PPD preparation 291 were determined from guinea pig assays. Using the assayed potencies, it was concluded that doses of 0.08, 0.17, 0.24 and 0.47 mg of bovine PPD were used in single caudal fold tests in 2 trials of Northern Territory cattle. The sensitivity, specificity and test efficiency of the Australian preparations were determined. At 72 h after injection, the time recommended to read the test, the 0.08 mg dose gave the lowest sensitivity (79.2%) which was significantly different from that of the other 3 doses. This dose also gave the highest specificity (88.9%). However, the 0.24 mg dose gave a specificity of 85.0% and a sensitivity of 95.6% resulting in the highest test efficiency (87.9%). Change in caudal fold thickness, subjectively assessed reaction and the amount of induration were measured in individual cattle. For tuberculous cattle, regression analysis showed significant relationships (p < 0.01) between the change in caudal fold thickness, subjectively assessed reaction and log concentration of each preparation. However, there was no significant difference between the mean responses observed with the 2 highest doses. Predicted responses for untested doses were determined from the regression equations. When the results of the trials were considered in relation to factors such as batch variation, minimisation of injection error, likely levels of desensitisation, cost and international implications, it was considered that a dose of 0.3 mg bovine PPD relative to the British standard 291 would fulfil optimum requirements for use in all parts of Australia. Copyright © 1979, Wiley Blackwell. All rights reserved