Evaluation of brucellin skin test for bovine brucellosis

The diagnostic efficiency of the Brucellin skin test for bovine brucellosis was evaluated using cattle of known history. The test was negative in six out of 14 heifers (42.9%) infected with virulent Brucella abortus (Br. abortus) strain 544. In four cattle vaccinated with a reduced dose of Br. abortus strain 19 vaccine (5 X 10(9) live organisms) the skin test became positive in all the animals but two weeks after immunization. However, all the vaccinates became negative 14 weeks after vaccination, whereas nine out of 14 heifers (64.3%) vaccinated with killed Br. abortus 45/20 adjuvant vaccine (Duphavac vaccine) were still positive 18 months post immunization. Four control cattle were persistently negative. It was considered that the procedure would be most useful for testing non-exposed cattle and should be used as a screen test. It is not useful as a diagnostic test for cattle immunized with Duphavac vaccine. A recommendation is made for interpreting the Brucellin skin test for the diagnosis of bovine brucellosis in non-exposed herds.