Evaluation of a new commercial test for the rapid serological diagnosis of canine brucellosis

WANKE, MARÍA M; CAIRÓ, F; ROSSANO, M; LAIÑO, M; BALDI, PC; MARTINEZ VIVOT, M

Buenos Aires

Congreso; Brucellosis 2011 International Research Conference; 2011

Asociación Argentina de Microbiología

As in other species, the diagnosis of brucellosis in the dog continues to be problematic. The most widely used screening test is the rapid slide agglutination test in the presence of 2-mercaptoethanol (2ME-RSAT) using whole cells of the M(-) strain of Brucella canis as antigen. The diagnosis is partially confirmed by agar-gel immunodifusion test (AGID) and definitively confirmed by bacteriological isolation. Some chronic cases that may not be detected by these tests may be detected by ELISA tests that use a hot-saline extract (HS) or cytosolic proteins of Brucella as antigens. The use of 2ME-RSAT in the routine clinical practice is complicated by the need of a microscope to read the reaction and an experienced operator to interpret the results. An immunochromatographic diagnostic test for canine brucellosis (FASTest® Brucella c., Megacor, Hörbranz, Austria) has been recently released, which is very simple to perform and could be potentially used in the routine clinical practice. In the present study we compared the diagnostic performance of the FASTest with those of 2ME-RSAT, AGID and ELISAs. Sera from 17 healthy dogs used as negative controls yielded negative results by FASTest, indicating a 100% specificity in this sample. Among 27 sera of dogs with acute or subacute brucellosis confirmed by B. canis isolation, all of which were positive by RSAT and ELISAs, the FASTest was positive in 24 cases and AGID in 23. In the 3 dogs negative by FASTest the test was repeated with casettes from other lot because the color of the control line on the reactive strips lightly differed from that indicated in the product insert; a positive result was obtained in 2 cases. Sera from 6 dogs with bacteriologically confirmed chronic brucellosis which were positive by ELISAs but negative by 2ME-RSAT were also tested; 1 resulted positive by FASTest and 4 by AGID. These preliminary results indicate a good specificity of the FASTest (100% in this sample). In acute and subacute cases the sensitivity of the test was 89% in the initial run and 96% if the re-assayed samples are considered. This later value, however, would not be statistically acceptable since the test was repeated due to the uncertain performance of a specific lot and on the basis of previously known results. In cases with chronic brucellosis the sensitivity of the FASTest was lower than that of ELISAs. It would be necessary to test a higher number of samples at least in duplicate to draw sound conclusions on the reliability of the FASTest as a screening tool for canine brucellosis.