Comparison of histologic techniques for the diagnosis of bovine tuberculosis in the framework of eradication programs.

Rapid diagnosis of tuberculosis in cattle reacting positive in antemortem assays is crucial in countries where eradication programs are operated to confirm the presence of the infection in tuberculosis-free herds. This study evaluated the accuracy of histopathologic examination by hematoxylin and eosin and Ziehl-Neelsen (ZN) staining applied in this framework, when suspected lesions are caused by low infectious doses and are detected in early stages of the disease. For this purpose, histologic methods were compared with mycobacterial culture as reference test on suspected lymph node samples from 173 cattle reacting positive in antemortem tests. Histopathology demonstrated high sensitivity (93.4%) and specificity (92.3%), while ZN sensitivity and specificity were respectively 33.9% and 100%. There was good agreement between histopathology and bacterial culture, suggesting that histopathologic examination is a reliable tool for rapid diagnosis in countries where active tuberculosis eradication programs allow the prompt identification and elimination of reactor cattle. Histopathology permits identification of typical mycobacterial lesions and its differentiation from other causes.