Scrapie Sheep

Definition

Scrapie is a fatal, neurodegenerative disease that affects sheep and goats. It is classified as a transmissible spongiform encephalopathy (TSE), a group of rare and incurable diseases that cause the brain and nervous system to deteriorate over time.

5 Must Know Facts For Your Next Test

1. Scrapie is one of the oldest known transmissible spongiform encephalopathies, with the first recorded cases dating back to the 18th century in the United Kingdom.
2. The disease is characterized by the accumulation of abnormal prion proteins in the brain, leading to neuronal degeneration and the formation of sponge-like holes in the brain tissue.
3. Scrapie is transmissible between sheep and goats through exposure to contaminated environments, feed, or contact with infected animals.
4. There is no known treatment or cure for scrapie, and the disease is always fatal, with affected animals typically dying within a few months to a few years after the onset of clinical symptoms.
5. Scrapie is not known to be transmissible to humans, unlike the related prion disease Creutzfeldt-Jakob Disease (CJD), which can be transmitted to humans through exposure to infected tissue or consumption of contaminated meat products.

Review Questions

• Describe the key features of scrapie that classify it as a transmissible spongiform encephalopathy (TSE).
  • Scrapie is classified as a transmissible spongiform encephalopathy (TSE) due to its underlying pathogenesis involving the accumulation of abnormal prion proteins in the brain. This leads to the characteristic sponge-like appearance of the brain tissue, as well as progressive neurodegeneration and ultimately, the fatal outcome of the disease. The transmissible nature of scrapie, which can be passed between sheep and goats through environmental exposure or direct contact, is another defining feature of TSEs.
• Explain the role of prions in the development and transmission of scrapie.
  • Prions, which are misfolded proteins, play a central role in the pathogenesis of scrapie. These abnormal prion proteins can induce the misfolding of normal prion proteins, leading to their accumulation in the brain. This accumulation of misfolded prions disrupts normal brain function and causes the characteristic sponge-like degeneration of brain tissue. The ability of prions to propagate and transmit this misfolding process is what allows scrapie to be transmitted between infected and uninfected animals, making it a highly infectious disease.
• Discuss the significance of scrapie in the context of other transmissible spongiform encephalopathies, such as Creutzfeldt-Jakob Disease (CJD) in humans.
  • Scrapie is significant in the broader context of transmissible spongiform encephalopathies (TSEs) because it was one of the first known TSEs and served as a model for understanding the pathogenesis of these rare, fatal neurodegenerative disorders. While scrapie is not known to be transmissible to humans, the related human TSE, Creutzfeldt-Jakob Disease (CJD), shares many similarities in terms of the underlying prion-based mechanism and the progressive degeneration of the brain. The study of scrapie has provided valuable insights into the nature of prion diseases, which has implications for the diagnosis, treatment, and prevention of related TSEs that can affect both animals and humans.

Related terms

Prion:

An infectious agent composed of a misfolded protein that can induce other normal proteins to misfold, leading to the development of transmissible spongiform encephalopathies like scrapie.

Transmissible Spongiform Encephalopathy (TSE): A group of rare, fatal neurodegenerative disorders caused by the accumulation of abnormal prion proteins in the brain, resulting in a sponge-like appearance of the brain tissue.

Creutzfeldt-Jakob Disease (CJD): A rare, fatal human neurodegenerative disorder caused by the accumulation of abnormal prion proteins, similar to the pathogenesis of scrapie in sheep.