Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 1/31/2018
Publication Date: 3/2/2018
Citation: Silva, C.J. 2018. Chronic wasting disease: Bambi vs. the prion. Northern California Branch American Society for Microbiology Spring Meeting, March 2-3, 2018. Session 2. Presentation 2.
Technical Abstract: Chronic wasting disease (CWD) was first described in Colorado in 1967 and subsequently recognized as a prion disease in 1980. CWD has a long and asymptomatic incubation period (> 1 year) followed by a short disease course that ends in the death of the animal. There is no known treatment or cure for prion diseases. Since its first description, CWD has been identified in 24 states, two Canadian provinces, Korea and Norway. CWD is the only prion disease spread by wild animals in their natural environment. It infects both farmed and wild cervids, including white-tailed deer, black-tailed deer, mule deer, elk (American), moose (American and European), red deer (European), and reindeer (European). CWD is caused by prions (PrPSc), which are infectious proteins, able to induce a normal cellular prion protein (PrPC) to refold into the prion conformation and, thereby, propagate an infection. PrPSc and PrPC are isosequential and possess identical covalent post-translational modifications. PrPSc is a multimer of refolded PrPC and resistant to proteinase K (PK) digestion while PrPC is monomeric and has no PK resistance. PrPC secondary structure is comprised of a small amount of beta-sheet (~ 5 %), a larger portion of alpha-helix (~ 28 %) and the remainder is unstructured. In contrast, the secondary structure of PrPSc is composed of beta-sheet and unstructured regions with no alpha-helix. The PrPC monomer is globular, while the monomeric portion of the multimeric PrPSc is believed to be a four-rung beta-solenoid. PrPSc can propagate more than one conformation (strain), each with its own distinct pathological phenotype. This means that more than one prion disease can infect a given host and that prions can respond, in a limited way, to selection pressures. In order words, they can evolve. There are a number of CWD prion strains that infect cervids. Some prion strains infect the brain and spinal cord, but only have a limited distribution of CWD prions throughout the lymphatic system. Cervids infected with other prion strains show a wide distribution of prions throughout the lymphatic system in addition to infecting the brain and spinal cord. As a result, CWD can be spread from animal to animal (horizontal) by normal contact. Furthermore, asymptomatic animals also shed prions in urine, feces, and saliva. These prions reside in the environment where they can be ingested, thereby infecting other animals. Prions are very stable, which means that they can remain infectious in a contaminated environment for years. Managing this disease is a substantial challenge.