Evaluating the brucellin skin test as an additional test to control bovine brucellosis

Abstract

Brucellosis is a bacterial disease of high veterinary importance, besides being a significant zoonosis worldwide. It is characterised by variable, and at times long and latent, incubation periods, which makes its control and eradication a challenging effort. No single test is able to identify all stages of the disease with high sensitivity. The brucellin skin test, which has been proved to identify some acute and chronic latent stages of brucellosis, has not been validated in South Africa. The objective of this study was to evaluate the brucellin skin test in brucellosis free, as well as confirmed infected cattle herds, under South African commercial farming conditions. The results indicate that the brucellin skin test has a high specificity (99.2% (95% confidence interval (CI): 98.1% – 99.7%)), and that despite a relatively low sensitivity (42.9 % (95% CI: 30.5% – 56.0%)), it was able to identify all the infected herds and detect more infected heifers in infected herds when compared to the routinely used Rose Bengal Test and Complement Fixation Test. It was concluded that the brucellin skin test could be used in parallel with serological tests to improve the sensitivity of the current diagnostic strategy in chronically infected herds where eradication of the disease has proven problematic. Removal of more infected heifers would decrease infection pressure and streamline vaccination towards heifers not exposed to Brucella abortus.