Canine brucellosis. Current status of methods for diagnosis

A critical review of the performance of several methods used for the serodiagnosis of canine brucellosis is presented. It is concluded that none of the procedures commonly used is, in itself, adequate to permit a definitive diagnosis in all cases. The diagnosis is simplified when several animals in a kennel are infected; however individual cases pose a variety of problems, especially when complete clinical histories are not submitted or opportunities for infection have not been disclosed. Blood cultures are an essential part of the laboratory diagnosis of B. canis infection, but bacteremia is frequently absent in chronically infected dogs. Judgements must therefore be made on the basis of bacteriologic results in concert with a variety of serologic tests, and an evaluation of clinical signs. In some instances, laboratory diagnosis is not possible without repeated samplings. The minimal diagnostic effort should include the screening of sera by the slide agglutination test (SAT). Negative results, in the absence of clinical signs, strongly suggest absence of infection. Positive SAT results indicate that further laboratory study is required. A two-stage testing procedure of all SAT-positive serums is therefore recommended. The tube agglutination test (TAT) or the 2-mercaptoethanol-TAT (ME-TAT) are valuable complementary methods; however either of these latter procedures, in conjunction with immunodiffusion analysis, appears to provide the best chances for accurate judgements of serologic results in difficult cases.