Comparison of the complement fixation test and the indirect hemolysis test for cattle vaccinated and infected with Brucella abortus.

The complement fixation test (CFT) and indirect hemolysis test (IHLT) were applied to sera collected from 60 cattle challenged with Brucella abortus 544. Of the 60 cattle, 48 were vaccinated with either B. abortus 19 or B. abortus 45/20 as calves or as adults. The remaining 12 cattle were not vaccinated. Of the 27 sera from cattle found to be infected, 9 showed aberrant reactions to the CFT. The advantages of the IHLT for these cattle were as follows. After challenge, the titers to the IHLT became positive earlier than or at the same time as the titers to the CFT, they persisted longer than the titers to the CFT, and they failed to show prozone reactions, which are a problem with the CFT. An additional advantage was that before challenge and after vaccination with strain 19, the titers to the IHLT rose later and declined earlier than the titers to the CFT. We concluded that the CFT used in conjunction with the IHLT improves the detection of infected cattle.