Diagnosis of canine brucellosis by detection of serum antibodies against an 18 kDa cytoplasmic protein of Brucella spp.

An antigenic capture ELISA was developed to measure serum antibodies against an 18 kDa cytoplasmic protein of Brucella. This assay was used to detect anti-18 kDa reactivity in sera from 30 dogs having confirmed or suspected brucellosis. Antibodies against the 18 kDa protein were found in 26 of them, which were also positive by the slide agglutination test (2ME-RSAT). The overall correlation (positive and negative results) between the ELISA and 2ME-RSAT tests was 93.3%. Additionally, these sera were assayed by an indirect ELISA using a whole extract of cytoplasmic proteins of B. abortus (LPS-free CYT). The results of both ELISAs were coincident in 28 of 30 (93.3%) dogs having confirmed or suspected brucellosis. When a serological follow-up was performed on some dogs having confirmed brucellosis, antibody titers measured by both ELISAs showed a parallel progression. On the other hand, the capture ELISA showed good specificity, since a positive result was obtained only in 2 of 103 sera from healthy dogs. These preliminary results show that the ELISA for detecting serum antibodies against the 18 kDa cytoplasmic protein of Brucella could be useful for the diagnosis of canine brucellosis. This study also shows that the results obtained with this single protein of Brucella are equivalent to those obtained with the whole extract of cytoplasmic proteins.