Diagnostic interaction between bovine tuberculosis (bTB) and Johne's disease in bTB highly prevalent dairy farms of Uruguay

The consolidation of the dairy industry, with increase in sizes, density and productivity of the herds, was associated to unprecedented bovine tuberculosis (bTB) prevalence levels in dairy herds in Uruguay, where Johne's disease (JD), another mycobacterial disease, is also prevalent. Here, we aimed to characterize the association between bTB- and JD-diagnostic results in two heavily bTB- and JD-coinfected dairy herds. Results from bTB-intradermal tests and JD-ELISA in 686 cows indicated a significantly (P < 0.001) higher frequency of bTB-positive animals in the JD-positive population, in which a significantly lower agreement between the caudal and cervical comparative intradermal tests was observed, compared to the JD-negative population. These findings suggest a significant association between the detection of these mycobacterial diseases, that may affect the performance of the routine bTB diagnostic tests performed in dairy herds in Uruguay.