Fluorescence polarization assay: Diagnostic evaluation for porcine brucellosis.

Brucellosis in pigs, caused by the bacterium Brucella suis, is an important zoonotic infection. In the present study, fluorescence polarization assay (FPA) was standardized and compared with indirect enzyme linked immunosorbent assay (iELISA) and competitive ELISA (cELISA) for diagnosis of porcine brucellosis. Test performances were evaluated using representative panel (n = 100), samples from swine brucellosis outbreak (n = 300), samples from brucellosis suspected animals (n = 291) and sera samples from apparently healthy animals (n = 1121). With panel samples, the FPA cut-off ≥11ΔmP was arrived with sensitivity (Se) and specificity (Sp) of 95.00 and 98.75%, respectively. Testing of samples from swine brucellosis outbreak, the diagnostic Se and Sp of 100 and 95.14% by iELISA, 73.91 and 100% by cELISA and 86.96 and 100% by FPA, respectively were recorded. Similarly, in case of swine brucellosis suspected samples, relative performance of FPA with cELISA had revealed higher kappa value of 0.864 with an accuracy of 93.47. Indirect ELISA was found to be highly sensitive but showed cross reactivity mainly for Yersinia enterocolitica O9 antibodies than cELISA and FPA. The high specificity of FPA test recorded in various types of samples in the study indicated that, FPA could serve as confirmatory test for individual animal diagnosis, outbreak confirmation, surveillance and quarantine of swine brucellosis cases.