Brucellosis in elk III. Serologic evaluation

The efficacy of the standard plate agglutination (SPT), buffered Brucella antigen rapid card (BBA), rivanol (Riv) and complement fixation (CFT) tests was statistically evaluated and correlated with known brucellosis infections in elk. Low titers on the SPT were detected in artificially exposed mature cow elk 2 weeks postinoculation and other tests began detecting antibodies at 3 weeks. Titers on all tests were detected as long as 4 years postinoculation. Serologic response was similar in artificially and naturally infected cows. Bulls did not maintain serologic titers as long as cows. The SPT at 1:25 or higher most frequently detected Brucella antibodies in infected elk, while the SPT at 1:100 or more least frequently detected antibodies. The percent of elk reacting at 1:100 or greater on the SPT declined rapidly after 6 months postinoculation. Combinations of any 2 of the 4 tests used had close agreement in concurrently identifying infected elk. The CFT correctly identified the greatest number (93%) of elk which were culture positive at necropsy and CFT titers persisted longer than those of the other tests. A CFT reaction persisted longer (average 10.7 weeks) than that of any other test in calves that demonstrated postnatal titers. The serologic responses of calves which acquired active infections were similar to adults. Criteria for identifying seropositive elk are discussed.