Comparison of serologic tests and bacteriologic culture for detection of brucellosis in swine from naturally infected herds.

Objective: To compare results of 6 serologic tests with results of bacteriologic culture for Brucella suis in swine.
Design: Prospective study.
Animals: Two hundred twenty-one swine from 39 naturally infected herds.
Procedure: Blood samples and lymph nodes were collected at slaughter. Serologic tests conducted were the particle concentration fluorescence immunoassay, the automated complement fixation assay, the card test, the buffered acidified plate antigen assay, the standard tube test, and the rivanol test. Lymph nodes were plated on Farrell's medium and serum-enriched agar for bacteriologic culture.
Results: Sensitivities ranged from 57 (automated complement fixation assay) to 83% (standard tube test). Specificities ranged from 62 (standard tube test) to 95% (rivanol test). Brucella suis was isolated from 46 of the 221 (21%) pigs. For 8 of the 46 culture-positive pigs, results of all 6 tests were negative.
Clinical Implications: Data illustrate the difficulty of eliminating brucellosis by means of a test-and-removal program and support the policy of slaughtering infected herds.