Introduction:
Transmissible spongiform encephalopahties (TSEs) are an unusual group of diseases characterized by the presence of numerous small cavities in the brains of affected individuals. These cavities are caused by the loss of neurons, and can take decades to form following the initial infection by the causative agent.
TSEs include scapie in sheep, bovine spongiform encepholopathy (BSE( or “mad cow” disease, chronic wasting disease in deer, and Creutzfeld-Jakob disease (CJD) in humans.
TSEs can be transmitted experimentally by injecting infected brain tissue into a recipient animal’s brain. TSEs can also spead via tissue transplants and apparently by consumption of tainted food. In the late 20th century, the disease kuru was discovered among member of the Fore people of Papua New Guidea. These members engaged in ritualistic consumption of their dead which lead to the spread of a commonly fatal TSE through the tribes.
Mad cow disease spread widely among cattle herds of England in the 1990s becasuse cows were fed bone meal prepared form sheep and cattle carcasses to increase the protein content of their diet. Like the Fore, teh cattle were eating the tissues of animals that had died of the disease.
CJD is the most comon prior disease –hstorically linked to eating beef from cattle infection with BSE. It is very rare. Only four vCJD cases have ever been repsorted in the US, all in people believed to ahve been exposed abroad.
Causes:
TSEs are caused by prions (proteinaceous infectious particles). Prions are imply proteins folded into the wrong shape, and that structural mistake can cause devastating problems. Prions are infectious forms of naturally occurring proteins that can alter healthy proteins and lead to neuronal cells death. One prion can trigger a chain reaction, coaxing neighboring proteins to misfold too, and the damage spreads through the brain.
Prion diseases are called transmissible spongiform encephalopatheis (TSEs) and they include bovie spongiform enceophalpathy (BSE), better known as mad cow disease, and Creutzfeldt-Jakob disease (CJ). Once symptoms of CFD appear, a perons’ decleine is often fast, and it is always fatal.