Scrapies, in sheep and goat

Transmissible spongiform encephalopathies (TSEs)—Brain diseases transmitted from one animal to another. Under a microscope, the brain tissue of animals and people with TSEs resembles a sponge. TSEs include variant Creutzfeldt-Jacob disease (vCJD) in humans, scrapie in sheep and goats, and bovine spongiform encephalopathy (BSE) in cows (mad cow disease). These diseases are spread by consumption of brain tissue and are thought to be caused by prions, a kind of protein. 

Dickinson AG (1976) Scrapie in sheep and goats. In Kimberlin RH (ed) Slow virus diseases of animals and man. North-Holland Publishing, Amsterdam, pp 209-241... 

As more infectious prions are created, they aggregate together into fibrils, and it is these fibrils that appear to induce disease. Prions are the cause of a number of degenerative brain diseases, including bovine spongiform encephalopathy or mad cow disease in cattle, scrapie in sheep and goats, chronic wasting disease in the wild cervids (the deer, moose, and elk), and Creutzfeldt-Jakob disease in humans. 

Scrapie is a neurodegenerative disease with a long incubation period, known to occur in sheep and goats, however, mice and other small rodents can be infected with it (Hunter, 1972). Certain scrapie strains induce obesity in... 

There are other diseases caused by misfolded prions that have similar symptoms. Kuru— transmitted through cannibalism—has been found to occur in the Fore people of Papua New Guinea (kuru means trembling ). Scrapie affects sheep and goats. This disease got its name from the tendency of sheep to scrape off their wool on fences as they lean on them in an attempt to stay upright. It is thought that mad cow disease, first reported in the U.K. in 1985, was caused by cows eating bone meal made from scrapie-infected sheep. 

Transmission of a TSE was first achieved by Cuille and Chelle, who managed to infect healthy sheep and goats by intracerebral inoculation of spinal marrow homogenates from sheep suffering from scrapie. Conclusive evidence for the infectious nature of TSE came from long-term inoculation experiment, which succeeded in transmitting CJD and Kuru to chimpanzees. 

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