Abstract :
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.
