Effect of Mycobacterium avium subsp. paratuberculosis (MAP) infection on the diagnostic accuracy for Mycobacterium bovis (M. bovis) infection under field conditions in cattle belonging to low M. bovis prevalence herds.

Abstract

Currently, the Chilean authority has implemented a National Eradication Program for bovine tuberculosis (bTB), aimed at controlling and eradicating the disease in Chile. The area under study has a low within-herd prevalence, has a relatively low number of infected herds, and is one of the major milk and beef producing areas in the country. However, so far, no attempts at eradicating the disease have been successful. It has been suggested that the diagnostic tests used were either not sensitive or specific enough. In addition, previous studies have shown that a great number of herds are infected with Mycobacterium avium subsp. paratuberculosis (MAP). The present study estimates the effect of MAP infection under field conditions, on the diagnostic sensitivity and specificity of routine tests in live animals for Mycobacterium bovis infection diagnosis in cattle. In general, the estimations of test accuracy observed an increase in the sensitivity and specificity on MAP-infected animals for tuberculin test but observed a decrease in the sensitivity of gamma interferon tests for MAP-infected cattle. These results are different from those of previous studies considering the role of MAP infection as an interfering infection. More research is needed in order to understand the complex interactions of the different mycobacteria that can be found infecting production cattle.