SPECIFICITY OF THE SKIN DELAYED-TYPE HYPERSENSITIVITY TEST IN BRUCELLOSIS FREE CATTLE TESTED WITH A BRUCELLA ALLERGEN

A study was conducted to determine possible nonspecific skin delyed-ty pe hypersensitivity (SDTH) test reactions in cattle tested with a Bruc ella allergen. Cattle (n = 14) experimentally inoculated with microorg anisms known serologically to cross-react with Brucella and cattle (n = 549) from Brucella free herds were tested serologically and with the SDTH test. The increase in skinfold thickness at the injection site o f the allergen was measured to the nearest mm with calipers 48 hours a fter injection. The results show that none of the SDTH test reactions in cattle experimentally inoculated with microorganisms other than Bru cella exceeded 2,0 mm. This indicates that an increase in skin-fold th ickness greater-than-or-equal-to 2,0 mm can be considered a positive S DTH test reaction. When this norm was applied to cattle in Brucella fr ee herds 11/549 (2 %) cattle showed an increase greater-than-or-equal- to 2,0. It is concluded that infections with microorganisms other than Brucella are unlikely to cause sensitization that interferes with the SDTH test when used to detect brucellosis. Therefore, the SDTH test c an be used to verify positive serologic tests results that might have been caused by microorganisms that serologically cross-react with Bruc ella.