Performance of two candidate bovine tuberculins in the intradermal tuberculin test in South African cattle naturally infected with Mycobacterium bovis

Abstract

The International Standard Bovine Tuberculin (ISBT) was confirmed for use in 1986 and serves as an internationally accepted reference for calibration and quality control. The World Health Organization has been involved in the production of a standard bovine tuberculin since 1976. More recently, the OIE in collaboration with the WHO coordinated a project for the development and testing of a new ISBT. By means of the international collaborative study, the performance of the ISBT against two new candidate tuberculins A and B, at two different concentrations in different regions of the world was tested. This study formed part of this international collaboration and tested the performance of the candidate tuberculins A (CA-1; 0.02mg, CA-2; 0.1mg) and B (CB-1; 0.02mg, CB-2; 0.1mg) in naturally infected cattle in South Africa. In order to test the performance of the candidate tuberculins A and B and the ISBT, 130 animals from known bovine tuberculosis positive herds were sampled. The BOVIGAMTM assay was used to identify 24 animals from the 130 animals, that were bovine tuberculosis positive and these animals were selected for the intradermal tuberculin testing. Evaluation of the performance of candidate tuberculins was done by comparing the skin test reactions of the tuberculins with the skin test reactions of the current ISBT. The means of the skin fold increases in the ISBT was compared to the means of the skin fold increases in candidates A and B. These were compared using ANOVA in excel analysis package, and the results indicated that there was no significant difference between the ISBT and the candidates A and B. The different concentrations in the tuberculins also did not register any significant difference in reactions and there was also no significant difference in the performance of the tuberculins on the different sides of the bovine neck. The clinical signs at the injection sites of both the ISBT and the candidate tuberculins were compared using ANOVA in excel analysis package and the p values were also >0.05 which indicated a lack of a significant difference between them. These results suggest that the candidate tuberculins A and B worked as effectively and gave similar skin responses to the current ISBT and may be considered for field diagnosis of bovine tuberculosis.