Comparison of Ziehl-Neelsen staining and immunohistochemistry for the detection of Mycobacterium bovis in bovine and caprine tuberculous lesions.

The avidin-biotin complex peroxidase (ABC-P) method was used to detect Mycobacterium bovis, and the results were compared with those obtained by the Ziehl-Neelsen (ZN) technique. Lesions were examined from 18 cows and 24 goats with tuberculosis. All animals showed pulmonary lesions, which in the cattle were mainly minor (i.e. primary complex) but in the goats were sometimes minor and sometimes severe. Microscopically, typical granulomas were seen in the lungs and lymph nodes, with central necrosis and the cellular components of chronic inflammation, but mycobacteria were either seen in small numbers or were not detectable. The ABC-P technique was more sensitive than the ZN method, as shown by the number of positive animals detected, the intensity of staining, and the successful use of low magnification. Caprine lesions, although more severe than bovine lesions, appeared to contain fewer organisms.