Histologically, multiple microgranulomatous foci are the characteristic inflammatory response. These consist of macrophages, monocytes and macrophage-derived multinucleated giant cells. The target cells of the virus are the macrophages. These inflammatory nodules occur chiefly in the hemispheric white matter, basal ganglia, thalami, brain stem, and cerebellum. The spongiform encephalopathies are a group of human and animal diseases caused by proteinaceous infectious agents called prions.
Prions are highly virulent and resist standard sterilization procedures.