Application of Bayesian modeling for diagnostic assays of Mycobacterium avium subsp. paratuberculosis in sheep and goats flocks

This study aimed to screen the sera of goats and sheep from flocks suspected of Mycobacterium avium subsp. paratuberculosis (MAP) infection by a newly standardized Mce-truncated ELISA (Mt-ELISA) kit for the detection of antibodies against MAP. Four diagnostic applied tests were evaluated including Indigenous plate-ELISA (IP-ELISA), Mt-ELISA, fecal Polymerase Chain Reaction (f-PCR) and fecal culture (FC).

Assuming the absence of a gold standard, latent-class models in a Bayesian framework were used to estimate the diagnostic accuracy of the four tests for MAP.

Mt-ELISA had higher Sensitivity (Se) in sheep (posterior median: 0.68 (95% Probability Interval (PI): 0.43-0.95), while IP-ELISA recorded the highest Se in goats as 0.83 (95% PI, 0.61-0.97). The f-PCR Se estimate slightly differed between species [sheep 0.36 (0.19-0.58), goats 0.19 (0.08-0.35)], while the Se of FC was similar between species [sheep 0.29 (0.15-0.51), goats 0.27 (0.13-0.45)]. The specificity estimates for all tests were high, close to unity, and similar between species.

Overall, the results showed that the Mt-ELISA method can be used for MAP detection in small ruminants' flocks.