An intradermal test for the diagnosis of brucellosis in extensively managed cattle herds

The application of a delayed hypersensitivity test for the diagnosis of bovine brucellosis was examined in a series of field experiments. The test is based on the intradermal injection of ‘Brucellin’, a lipopolysaccharide-free protein extract of Brucella abortus strain 45/20.

The Brucellin test was compared with the complement fixation (CF) test in 8656 cows of mixed age and known vaccination and herd status. An intradermal injection of 0.1 ml of the allergen was made in either the cervical region or the caudal fold. The injection site was examined 72 h after administration of Brucellin and any increase in skin thickness of 2 mm was regarded as positive.

When administered into the caudal fold site the Brucellin test had a sensitivity relative to the CF test of between 52 ± 14% and 61 ± 6%. The relative specificity of the test exceeded 99%.

Calfhood vaccination with B. abortus strain 19 did not result in positive Brucellin test results. There was no evidence that the injection of Brucellin induced a serological response.

Despite the low relative sensitivity of the Brucellin test, it is a useful low-cost tool for identifying infected herds. It is a least as effective as slaughterhouse surveillance systems.