Classification of lesions and comparison of immunohistochemical and acid fast staining in diagnosis of naturally occurring paratuberculosis in goats

Lesions associated with paratuberculosis and degrees of positivity by Ziehl-Neelsen (ZN) and Avidin–Biotin Complex peroxidase (ABC) techniques in 26 adult goats grossly or clinically suspected to paratuberculosis were studied. Of these, 17 (65.4%) had microscopic lesions associated with paratuberculosis which were classified into three categories. Diffuse multibacillary lesions (30.8%) characterized by a diffuse granulomatous enteritis with epithelioid macrophages infiltration as main inflammatory cells into lamina propria that arranged mosaic-like appearance, and filled with numerous acid fast bacilli in ZN and highly positive in ABC. Diffuse lymphocytic lesions (11.5%) composed of lymphocytes as main inflammatory infiltrate, with some epithelioid macrophages or giant cells containing few if any mycobacteria. Diffuse mixed lesions (23%) characterized by a diffuse granulomatous enteritis with infiltration of mixture of large numbers of lymphocytes and epithelioid macrophages with varying degrees of positivity in ZN and ABC. In all types of lesions, other lesions such as granulomatous lymphangitis and arteritis, lymphangiectasis, thrombi composed of degenerated epithelioid macrophages were observed. Caseous necrosis, calcification and fibrosis in mesenteric lymph nodes commonly, especially in diffuse lymphocytic form, were observed. In conclusion, the present study showed three categories of lesions in which diffuse multibacillary form was the commonest type. Both ABC and ZN methods can detect (ABC with more positivity) almost all the goats with diffuse multibacillary and mixed lesions; more cases with lymphocytic forms were positive by ABC than by ZN. ABC method seems to be an efficient diagnostic adjunct to conventional ZN staining for diagnosis of paratuberculosis in goats. The importance of sampling the ileum (especially ileocecal valve), jejunum and mesenteric lymph nodes to find microscopic lesions of paratuberculosis in goats is emphasized.