Estudo comparativo de métodos complementares para o diagnóstico da tuberculose bovina em animais reagentes à tuberculinização Comparative study of complementary diagnostic methods of bovine tuberculosis on skin-test reactive cattle

Bovine tuberculosis is an infectious disease of world-wide occurrence. The intradermal tuberculin test is the standard test for its detection, but it can lack both sensitivity and specificity. The purpose of this study was to compare the efficiency of different complementary methods for the diagnosis of bovine tuberculosis such as macroscopic, histopathological, bacteriological analysis and Enzyme-linked immunosorbent assay (ELISA). A total of 97 skin-test reactive animals were studied, and tissues and serum samples were collected from all of them at the moment of the slaughter. Seventy animals (72.16%) showed macroscopic lesions suggestive of tuberculosis. At the histopathological exam, sixty three (64.95%) presented typical granulomatous lesions. Therefore, histopathology agreed with macroscopic inspection in 92.78% of the samples. Acid-fast bacilli were observed in tissues samples from 47 (48.45%) animals, all of them also positive either at macroscopic inspection or to histopathology. In reference to the bacterial culture, only 11 (11.34%) tissues samples yielded Mycobacterium bovis. Thirty three (34.02%) serum samples were reactive at ELISA. Detailed visual inspection as well as histopathology, due to its high specificity, are suggested as complementary tools and may be used for confirming doubtful cases of bovine tuberculosis at the slaughterhouse.