The efficacy of the skin delayed-type hypersensitivity using a brucellin prepared from a mucoid strain of Brucella abortus to detect brucellosis

Eight-hundred-and-ninety-six cattle belonging to herds officially designated Brucella-free, and 190 cattle belonging to infected herds were tested with the skill delayed-type hypersensitivity (SDTH) test, using brucellin (273) prepared from a mucoid strain of Brucella abortus. An increase in skinfold thickness greater than or equal to 2mm was considered a positive SDTH test. The serum agglutination test, complement fixation test and bacteriological examination were used to confirm SDTH test results. Results show that 6 of the 896 uninfected cattle tested positive in the SDTH test, indicating a 99.3% specificity. Of the 44 cattle that tested serologically or bacteriologically positive, 33 tested positive in the SDTH test, indicating a 75% sensitivity. The value of the SDTH test was demonstrated by its ability to detect infection earlier than serological tests, and by confirming infection in cattle with ambiguous serological test results. An increase in skinfold thickness greater than or equal to 1 mm in cattle in suspected herds should not be ignored, as it may indicate specific sensitization. We recommend the use of the SDTH test in combination with serological tests for early diagnosis of brucellosis in cattle.