Comparison of enzyme-linked immunosorbent assay and complement fixation test for the detection of specific antibody in cattle vaccinated and challenged with Brucella abortus.

An enzyme-linked immunosorbent assay (ELISA) and a complement fixation test (CFT) were applied to sera collected regularly from 60 cattle challenged with Brucella abortus strain 544. Of the 60 cattle, 48 were vaccinated with either B. abortus strain 19 or B. abortus strain 45/20 as calves or adults. The remaining 12 cattle were not vaccinated. Of the 27 sera from cattle found to be infected at slaughter, 9 showed aberrant reactions to the CFT in that a positive titer after challenge was delayed or transient. The performance of the ELISA in these nine cattle with aberrant reactions and the other cattle in the trial was as follows. After vaccination with strain 19 or strain 45/20, the number of weeks at which the ELISA was positive was significantly greater (P less than 0.001) than that for the CFT. The strain 19 vaccine also induced positive responses to the CFT and the ELISA for a significantly longer period (P less than 0.001) than did the strain 45/20 vaccine. For cattle with aberrant reactions, the number of weeks after challenge when the ELISA was positive was significantly greater (P less than 0.001) than that for the CFT. For noninfected cattle, the average number of weeks after challenge when the CFT was negative (35 of 40) was higher than that for the ELISA (18 of 40).