Fibrils in brains of Rocky Mountain elk with chronic wasting disease contain scrapie amyloid

Chronic wasting disease (CWD), a progressive, fatal neurological disorder of captive mule deer and Rocky Mountain elk, is characterized neuropathologically by spongiform change in the neuropil, intraneuronal vacuolation and astrocytic hypertrophy and hyperplasia. Recently, scrapie amyloid-immunoreactive plaques have been demontrated in brain tissues of CWD-affected captive mule deer, Rocky Mountain elk and hybrids of captive mule deer and white-tailed deer. We now report on the presence of abnormal fibrils isolated from brain tissues of Rocky Mountain elk using negative-stain electron microscopy. These fibrils resemble those found in scrapie-infected hamster brain. Furthermore, protein bands with relative molecular masses of 26 to 30 kilodaltons were shown to be immunoreactive to antibodies raised against scrapie amyloid by Western immunoblotting. Immuno-dot blot showed similar reactivity. Our data support the clinical and pathological diagnosis of the disease and provide further evidence that CWD belongs to the subacute spongiform encephalopathies.