Bovine spongiform encephalopathy, or "mad cow disease," is an infection that attacks a cow's nervous system and deteriorates the brain, KidsHealth states. The disease triggers changes in behavior and causes cows to lose control of important bodily functions. An outbreak is cause for concern because humans who consume contaminated meat are at risk of contracting a variant form, known as Creutzfeldt-Jakob disease, or vCJD.
Although mad cow disease can be transmitted through consumption, it isn't contagious, KidsHealth states. The disease's source isn't certain, but the contagion may be present in types of cow feed, especially food containing dead cow remains.
In humans, vCJD progressively erodes the nervous system until death, causing neurological symptoms, such as depression, dementia and impaired coordination, WebMD notes. Research suggests the disease develops when a prion, a type of protein, undergoes abnormal mutation and attacks tissue in the brain and spinal cord. The infectious substance isn't harmed by heat exposure, so cooking infected meat doesn't sterilize it.
Cases of mad cow disease are extremely rare in the United States because the government regulates the importation and care of livestock. Importing live animals from countries exposed to mad cow disease has been banned since 1989, and tissue from the central nervous system isn't allowed in food products, according to WebMD. High-risk livestock, such as cows with impaired motor functions, are also kept out of the food supply.