Abstract:
Wesselsbron disease (WSL) was diagnosed in a 2-d-old lamb on a farm in the north-eastern Free State
Province where a few abortions and neonatal deaths occurred in sheep in April 1994. The liver of the lamb
was slightly swollen and orange-brown and, microscopically, it revealed single or small groups of necrotic
hepatocytes that were randomly scattered throughout the lobules. Other histopathologic hepatic lesions
included the presence of acidophilic bodies, intranuclear inclusion bodies in a few hepatocytes,
neutrophils in the parenchyma, mild Kupffer-cell and bile-ductular proliferation and infiltration of mixed
inflammatory cells in the portal tracts. Immunohistochemical staining of sections of formalin-fixed specimens
of the liver with polyclonal antibody against WSL virus revealed positive staining in acidophilic
bodies, cytoplasmic fragments of necrotic liver cells, the cytoplasm of degenerated hepatocytes and,
rarely, in intranuclear inclusions. Positive staining was also obtained in liver sections from two newborn
lambs experimentally infected with WSL virus.
The results of this investigation showed that the immunohistochemical staining of sections of formalin-fixed
liver can be used to confirm the diagnosis of WSL in new-born lambs.
