Comparison of complementary diagnostic methods of bovine tuberculosis on skin-test reactive cattle

ABSTRACT:

The aim of this study was to compare different complementary diagnostic methods (macroscopic, histological, serological and molecular) of tuberculosis in naturally infected cattle. The study was conducted from samples taken from 40 reagents cattle in cervical comparative intradermal tuberculin test (ITT). The macroscopic post mortem inspection of carcasses was followed by the collection of nasal swabs, blood and tissue samples (liver, lung and mediastinal lymph node) for polymerase chain reaction (PCR) test, Enzyme-Linked Immunosorbent Assay (ELISA) and histopathologic test with hematoxylin-eosin (HE) and Ziehl-Neelsen (ZN), respectively. Of the 40 cattle slaughtered, 22 (55%) carcasses had macroscopic lesions suggestive of tuberculosis. The histopathology HE identified 13 (32.5%) carcasses with histological changes: 6 (15%) in the mediastinal lymph nodes, 5 (12.5%) in the liver and 3 (7.5%) in the lung. At ZN, the presence of acid-fast bacilli was not detected in any of the samples tested. The ELISA/IDEXX^(r) identified one (2.5%) reagent animal, and the PCR test detected DNA of Mycobacterium bovis in one (2.5%) cow. It is concluded that among the diagnostic methods reviews none was able to detect all animals that were positive in tuberculin test, but the association of different methods can ensure diagnostic accuracy.

KEYWORDS:
Acid-fast bacilli; ELISA, Mycobacterium bovis; polymerase chain reaction; histopathology