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Bovine Spongiform Encephalopathy Fact Sheet - Pennsylvania Department Of Health - 2013

January 2, 2013

Bovine Spongiform Encephalopathy Fact Sheet

1. What is Bovine Spongiform Encephalopathy (BSE)?

a. BSE, often called “Mad Cow Disease,” is a fatal prion disease affecting the brain and

spinal cord of cattle. The word “prion” is an abbreviation for “infectious protein.”

b. Prions are abnormal variants of proteins that occur normally in cells, such as human brain

cells. Amazingly, when prions enter the body, they are able to convert their normal

counterparts into more of the abnormal forms.

c. The difference between the normal and abnormal proteins does not lie in their primary

structure (the sequence of their amino acids), but rather in their 3-dimensional folding.

The abnormal intracellular PrP proteins are folded in a way that allows them to resist

normal protease degradation so that over time this leads to the build-up of aggregates of

prions in the neurons in the brain.

d. Creutzfeldt-Jacob Disease (CJD) is a human prion disease. In both CJD and variant CJD

(vCJD), prions accumulate in the brain cells causing progressive brain damage, gait and

balance disturbances, difficulty swallowing, weight loss, behavioral changes and

eventually death.

e. When viewed at autopsy, stained tissue slides from the brains of animals or humans with

prion disease are filled with characteristic microscopic holes created by the excess

accumulation of abnormal prion proteins in the cells of the brain.

2. Where does BSE occur? - The vast majority of cattle with BSE have been reported from

Europe, especially the United Kingdom (U.K.). Human cases of vCJD resulted when people

ate infected parts of cattle with BSE. Most of the cases of this human disease were reported

from the U.K. and Europe ( ).

a. Through the end of 2012, more than 183,317 cases of BSE were confirmed in the United

Kingdom in more than 36,194 cattle herds.

b. The BSE epidemic in the U.K. peaked in January, 1993, at almost 1,000 new cases in

cattle per week. Through measures taken to protect the cattle feed supply, disease has

declined since then. Only 69 cases of BSE in cattle have been diagnosed in the U.K. since

2007, with only two of these in 2012.

c. The disease outbreak most probably originally resulted from feeding cattle with meat-

and-bone meal from sheep with a different type of prion disease called Scrapie. There is

strong evidence that the BSE outbreak was then amplified by feeding infected cattle

derived meat-and-bone meal to young calves as a feed supplement.

Bovine Spongiform Encephalopathy Fact Sheet - Pennsylvania Department Of Health - 2013