Abstract
INTRODUCTION: Paratuberculosis is a chronic wasting disease caused by Mycobacterium avium subsp. paratuberculosis (MAP). Control in herds relies on detecting infected animals, which are managed based on the level of MAP shedding. Faecal samples from seropositive animals are examined by bacterial culture and/or qPCR to detect MAP. The aim of this study was to evaluate the use of serology to predict the extent of MAP shedding. MATERIAL AND METHODS: A total of 139 serum and stool samples were tested. The sample-to-positive ratio (S/P) of the ELISA assay and the crossing point (Cp) of the qPCR test were used to estimate the relative amount of antibodies in serum and MAP in stool, respectively. Spearman's correlation was used to assess the relationship between S/P and Cp values. Further analyses tested the significance of differences in S/P ratios between groups of animals categorised by their level of MAP shedding. RESULTS: A weak-to-moderate correlation was found between S/P and Cp values (rs = -0.3471). Significant differences in S/P ratios were identified between groups of animals representing moderate-to-high and low MAP shedding. High MAP shedding was associated with an S/P ≥ 2.5. CONCLUSION: Our findings indicate that the ELISA test can be used to predict high MAP shedding. Despite the weak-to-moderate correlation between S/P and MAP levels in faeces, animals with an S/P ≥ 2.5 should be considered high shedders and removed from the herd without delay.