Chronic wasting disease detection in the lymph nodes of free-ranging cervids by real time quaking-induced conversion

Chronic wasting disease (CWD), a transmissible spongiform encephalopathy of deer, elk and moose, is the only prion disease affecting free-ranging animals. First identified in northern Colorado and southern Wyoming in 1967, new epidemic foci of the disease have since been identified in additional states, as well as two Canadian provinces and the Republic of South Korea. Identification of CWD-affected animals currently requires post-mortem analysis of brain or lymphoid tissues using immunohistochemistry (IHC) or an enzyme linked immunosorbent assay (ELISA), with no practical way to evaluate potential strain types or investigate the epidemiology of existing or novel foci of disease. Using a standardized real time quaking induced conversion (RT-QuIC) assay, a seeded amplification assay employing recombinant prion protein as a conversion substrate and Thioflavin T (ThT) as an amyloid-binding fluorophore, we blindly analyzed 1243 retropharyngeal lymph node samples from white-tailed 35 deer, mule deer and moose, collected in the field from current or historic CWD-endemic areas. RT-QuIC results were then compared with those obtained by conventional IHC and ELISA, and amplification metrics using ThT and Thioflavin S examined in relation to clinical history of the sampled deer. The results indicate that RT-QuIC is useful in both for identifying CWD-infected animals and facilitating epidemiologic studies in CWD endemic and non-endemic areas