Chronic Wasting Disease (CWD) is a contagious neurological disease that affects deer and other cervids. CWD is classified as a transmissible spongiform encephalopathy (TSE) disease also known as a prion disease. Prions are misfolded cellular proteins located on the surface of cells that infect and change other cellular proteins as they spread and accumulate in the body. It is not yet understood exactly how the prion proteins (PrP) are infected and structurally changed but once infected, CWD and all other TSEs are, after a prolonged incubation period, irreversibly fatal. As the prions accumulate in the brain, microscopic holes called vacuolar degenerations develop giving the brain a sponge-like appearance, hence the name "spongiform" (see Figure 1).
Figure 1: A comparison of healthy brain tissue (left) and tissue showing signs of vacuolar degenerations, astrocytosis, and amyloid plaque accumulation common to TSE diseases (right).