Use of an enzyme-linked immunosorbent assay in a bovine brucellosis eradication program.

An enzyme-linked immunosorbent assay (ELISA) was developed and was compared with the complement fixation test (CFT) in a bovine brucellosis eradication program. The ELISA detected significantly more reactors than the CFT in both strain 19 vaccinated infected herds (1.79% versus 1.14%) and non-vaccinated infected herds (4.2% versus 3.59%) but not in either vaccinated or non-vaccinated brucella-free herds. The specificity for both tests in brucella-free herds was greater than 0.998. The specificity and sensitivity of the ELISA were compared with those of 3 other tests (the Rose Bengal test; the indirect haemolysis test [IHLT] and the CFT) on serum from 151 animals cultured at slaughter. The calculated specificity of the ELISA in this infected group was lower than for both the CFT and the IHLT (0.58 versus 0.67 versus 0.75). The sensitivity however was much greater (1.0 versus 0.73 versus 0.71). The value of the ELISA when used in an eradication program is discussed.