Brucella ceti causes disease in Odontoceti. The absence of control serum collections and the diversity of cetaceans have hampered the standardization of serological tests for the diagnosis of cetacean
brucellosis. Without a "gold" standard for sensitivity and specificity determination, an alternative approach was followed. We designed an indirect
enzyme-linked
immunosorbent assay (iELISA) that recognizes
immunoglobulins G (IgGs) from 17 odontocete species as a single group. For the standardization, we used Brucella melitensis and Brucella abortus
lipopolysaccharides, serum samples from seven resident odontocetes with no history of
infectious disease displaying negative
rose bengal test (RBT) reactions, and serum samples from seven dolphins infected with B. ceti. We compared the performance of the iELISA with those of the
protein G ELISA (gELISA), the competitive ELISA (cELISA), and the immunofluorescence (IF) and dot blot (DB) tests, using 179 odontocete serum samples and RBT as the reference. The diagnostic potential based on sensitivity and specificity of the iELISA was superior to that of gELISA and cELISA. The correlation and agreement between the iELISA and the gELISA were relatively good (R(i/g)2 = 0.65 and kappa(i/g) = 0.66, respectively), while the correlation and agreement of these two ELISAs with cELISA were low (R(i/c)2 = 0.46, R(g/c)2 = 0.37 and kappa(i/c) = 0.62, kappa(g/c) = 0.42). In spite of using the same anti-odontocete
IgG antibody, the iELISA was more specific than were the IF and DB tests. An association between high antibody titers and the presence of neurological symptoms in dolphins was observed. The prediction is that iELISA based on broadly cross-reacting anti-dolphin
IgG antibody would be a reliable test for the diagnosis of
brucellosis in odontocetes, including families not covered in this study.