Prions: What Research Says About These Killer Proteins
© 2015 Health Realizations, Inc.
Proteins are generally beneficial for the human body, but when they are transformed into prions, they become deadly. Prions, which are mutated or improperly folded proteins, were only recently discovered in 1982, and researchers were surprised to learn that these agents were infectious, like viruses, and capable of causing fatal brain diseases.
Prions cause a variety of fatal brain diseases in both animals and humans.
Diseases caused by prions are known as transmissible spongiform encephalopathies (TSEs), and they include disorders that affect both humans and animals.
Prion Diseases in Animals
Bovine Spongiform Encephalopathy (BSE) – Mad Cow Disease (cattle)
Chronic Wasting Disease (CWD) (occurs in mule deer and elk)
Scrapie (affects sheep)
Transmissible mink encephalopathy
Feline spongiform encephalopathy
Ungulate spongiform encephalopathy
Prion Diseases in Humans
Creutzfeldt-Jakob Disease (CJD) (inherited or sporadic)
Variant Creutzfeldt-Jakob Disease (vCJD) (acquired from cattle with BSE)
Gerstmann-Straussler-Scheinker Syndrome (inherited or sporadic)
Fatal Familial Insomnia (inherited)
Kuru (once spread among people who practiced cannibalism in Paua New Guinea)
Normal prions occur naturally in the body and are harmless. But when a prion takes on a different folded shape than its normal counterparts, it becomes infectious. It's thought that once a prion becomes infectious, it alters other prions in a chain reaction.
The abnormal prions then clump together, which researchers believe may lead to neuron loss and brain damage. Prion diseases can also occur sporadically and may be inherited.
The Most Common Prion Disease
Creutzfeldt-Jakob Disease (CJD), the most common TSE, impacts about one person in every 1 million each year worldwide, including about 200 people annually in the United States.
In about 85 percent of cases, the disease is sporadic, meaning there is no known cause and no apparent risk factors. Another 5-10 percent of cases are hereditary, in which a person has a family history of the disease or tests positive for a genetic mutation linked to CJD. The third type of CJD, which is transmitted by exposure to brain or nervous system tissue via medical procedures or dietary sources, accounts for about 1 percent of cases.
The human form of mad cow disease, vCJD, can be transmitted by eating BSE-contaminated meat.
It’s possible to get CJD and other prion diseases through infected:
Grafts of dura mater (a tissue that covers the brain)
Implantation of inadequately sterilized electrodes in the brain
Injections of contaminated pituitary growth hormone derived from human pituitary glands taken from cadavers
Inoculation of prion-contaminated drugs
Use of prion-contaminated neurosurgical instruments
Consumption of contaminated beef or animal products
This latter form of infection, eating food made from cows with BSE, is thought to have caused about 208 cases of variant Creutzfeldt-Jakob disease (vCJD) annually worldwide. In all, there are typically more than 150 confirmed deaths from vCJD so far. It's thought that BSE was originally transmitted to cows because they were fed sheep meat infected with scrapie along with other cow parts that may have been infected.
Prior to 1997, cow parts not typically consumed by people were commonly added to animal feed.
Since August 1997, the U.S. Food and Drug Administration (FDA) has not allowed most parts from cows and certain other animals to be used in food fed to cows. In April 2009, the FDA also ruled that certain high-risk cow parts, such as brains and spinal cords from cows that are 30 months of age or older, could no longer be used to make animal feed, including pet food.
To date no one knows for sure how many people have had, or have, a form of TSE, because it's now becoming clear that some cases of dementia and Alzheimer's disease may actually have been TSE.
In fact, a recent study found a new form of prion disease that does not cause the typical sponge-like brain damage common to TSEs. Rather it resembles a form of Alzheimer's disease that damages brain arteries.
What Makes Prions Unique … and Particularly Deadly?
Prions are very different from infectious organisms like bacteria and viruses. They have no nucleic acids (DNA or RNA), and because they are not actually alive, and contain no genetic information, they cannot be killed by any of the typical methods of heating, sterilizing, etc.
They also have an unusually long incubation period. It can be up to 50 years from the time of exposure until symptoms appear.
There is currently no cure for any of the TSE diseases, including the human forms, CJD and vCJD, and the brain disease kills quickly once symptoms start.
Prion diseases cause small holes to develop in the brain (making it look like a sponge), which causes changes in personality, loss of body function and finally death.
So there is no test to detect prion-related diseases, no one knows for sure how long they can lie dormant before springing up, there is no treatment and there is no cure. Aside from humans, sheep and cattle, prion-related diseases have also been found in cats, mink, mule, elk and deer.
Getting your meat products from a small farmer that raises 100% grass-fed beef is a smart way to find high-quality, and typically safe, meat products.
At this stage, the only real way to prevent infectious prion diseases would be to take great care to stop including contaminated tissues, meat and more in animal feed and medical procedures, and stop feeding cow parts to other cows.
Though the FDA maintains that the “steps the FDA and USDA have taken to prevent cows in the U.S. from getting BSE are working very well,” you can take it a step further by getting your meat products from a small farmer that raises 100% grass-fed beef. Knowing where you beef products come from, including what they are fed, is essential to getting high-quality, disease-free meat.
Ideally, every cow should also be tested for the disease prior to entering the food supply, but this is currently not done. A new study did reveal that cattle infected with mad cow disease have a characteristic glow to their eyes, caused by chemical changes in the retina. This discovery could lead to the development of a new test to detect the infection and prevent BSE from contaminating the food supply.
In the worst outbreak of mad cow disease to date, 179,000 cattle in the United Kingdom were found to be infected with the disease, prompting the slaughtering of over 4 million cows in the ‘90s. It’s estimated that a “second wave” of vCJD may still hit the area, where it’s been warned that up to one in 4,000 people could carry the infection.
In the latest studies, however, researchers suggest that only a fraction of those infected will go on to develop the full-blown disease, and believe your DNA may control if and when the disease will manifest.
A blood test, the first of its kind, is also being developed that may be able to test for vCJD in blood transfusions.
U.S. Centers for Disease Control and Prevention
CDC: Prion Diseases
FDA.gov All About BSE
National Institute of Neurological Disorders and Stroke
eMedicine Prion-Related Diseases