How do prions cause mad cow disease. What are the symptoms of variant Creutzfeldt-Jakob disease. Can humans contract vCJD from contaminated beef. Is it possible to get vCJD from U.S. food products. How effective are current preventive measures against mad cow disease.

Understanding Mad Cow Disease: The Prion Connection

Mad cow disease, scientifically known as bovine spongiform encephalopathy (BSE), is a fatal neurodegenerative disorder affecting cattle. This mysterious ailment has sparked widespread concern due to its potential transmission to humans. The culprit behind this devastating condition is a misfolded protein called a prion.

Prions are abnormal versions of proteins normally found on cell surfaces. In BSE, these altered proteins wreak havoc on the central nervous system, specifically targeting the brain and spinal cord. The result is a progressive deterioration of neural tissue, leading to the characteristic “spongy” appearance of the affected brain.

The Prion Mechanism: A Molecular Domino Effect

How do prions cause such widespread damage? These rogue proteins act as molecular templates, inducing normal proteins to misfold and aggregate. This cascading effect leads to the accumulation of toxic protein clumps, disrupting cellular function and ultimately causing neuronal death.

• Prions are resistant to common sterilization methods
• They primarily affect nervous system tissue
• The exact trigger for initial prion formation remains unknown

From Cattle to Humans: The Emergence of vCJD

The human variant of mad cow disease, known as variant Creutzfeldt-Jakob disease (vCJD), has been linked to the consumption of BSE-contaminated beef products. This connection has raised significant public health concerns and led to stringent regulations in the meat industry.

Is vCJD a common occurrence in humans? Fortunately, cases remain rare. The Centers for Disease Control and Prevention (CDC) has identified only four deaths from vCJD in the United States, all believed to be caused by consumption of contaminated meat outside the country.

Distinguishing vCJD from Classic CJD

It’s crucial to differentiate vCJD from classic or sporadic Creutzfeldt-Jakob disease (CJD). Classic CJD occurs spontaneously at a rate of one to two cases per million people worldwide, regardless of beef consumption or exposure to mad cow disease. This form primarily affects individuals over 65 and progresses rapidly, usually proving fatal within six months of symptom onset.

Recognizing the Signs: Symptoms of vCJD

Variant Creutzfeldt-Jakob disease presents a diagnostic challenge due to its insidious onset and variable progression. Early detection is crucial for managing the condition and implementing appropriate care measures.

Early Stages: Neurological Disturbances

What are the initial symptoms of vCJD? In its early phases, the disease manifests with subtle neurological changes:

• Depression
• Anxiety
• Personality changes
• Loss of coordination

Disease Progression: Cognitive Decline

As vCJD advances, cognitive impairment becomes more pronounced. Patients may experience:

• Memory loss
• Confusion
• Difficulty with speech and vision
• Involuntary movements

In the later stages, dementia develops, significantly impacting the individual’s quality of life. Unfortunately, definitive diagnosis often occurs only in advanced stages when brain abnormalities become detectable through magnetic resonance imaging (MRI).

The Grim Prognosis: Life Expectancy and Treatment Options

How long can a person survive after being diagnosed with vCJD? The disease is invariably fatal, with most patients succumbing within 13 months of symptom onset. Currently, there is no cure or effective treatment to halt the progression of vCJD.

Medical interventions focus on managing symptoms and providing supportive care to improve the patient’s quality of life. Research into potential therapies is ongoing, with scientists exploring various approaches to target prion proteins and mitigate their harmful effects.

Safeguarding Public Health: Preventive Measures and Regulations

In response to the mad cow disease crisis, governments and health organizations worldwide have implemented stringent measures to protect public health and prevent the spread of BSE.

Import Restrictions and Feed Regulations

Since 1989, the United States has enforced strict import bans on live animals and certain meat products from countries with known cases of mad cow disease. These restrictions extend to ingredients used in human, animal, and pet foods.

Additionally, the use of ruminant-derived proteins in cattle feed has been prohibited, as this practice was identified as a primary factor in the spread of BSE in the United Kingdom during the 1980s and 1990s.

Enhanced Surveillance and Testing

The U.S. Department of Agriculture (USDA) has implemented comprehensive testing programs to monitor cattle populations for BSE. Hundreds of thousands of animals have been screened, with particular attention given to high-risk categories:

• Older cattle
• Animals unable to walk
• Cattle showing signs of neurological problems

Removal of Specified Risk Materials

To further reduce the risk of vCJD transmission, the USDA mandates the removal of specific tissues from cattle before they enter the food supply. These “specified risk materials” include:

• Brain tissue
• Spinal cord
• Parts of the small intestine
• Tonsils

By eliminating these high-risk tissues from the food chain, the potential for human exposure to BSE prions is significantly diminished.

Assessing the Risk: vCJD Transmission Through Food and Travel

Despite the alarming nature of mad cow disease and its human variant, the actual risk of contracting vCJD remains extremely low, particularly in countries with robust prevention and surveillance programs.

Safety of U.S. Beef Products

Can consumers contract vCJD from beef purchased in the United States? The likelihood is vanishingly small. The comprehensive measures implemented by the USDA and other regulatory agencies have created multiple layers of protection against BSE contamination in the food supply.

These safeguards include:

• Strict import controls
• Rigorous testing of cattle
• Removal of high-risk tissues
• Prohibition of certain feeding practices

Milk and Dairy Products

Is there a risk of contracting vCJD from milk or dairy products? Scientific evidence suggests that milk and milk products do not pose a significant risk for transmitting mad cow disease to humans. Experiments have shown that milk from BSE-infected cows has not caused infections in other animals.

Travel Considerations

What about the risk of acquiring vCJD while traveling abroad? According to the CDC, the current risk of contracting vCJD from any specific country appears to be extremely small. However, it’s important to note that precise risk assessment is challenging due to the global nature of food distribution networks.

Travelers concerned about potential exposure can take precautions such as:

• Avoiding beef products in countries with a history of BSE outbreaks
• Opting for well-cooked meat dishes
• Choosing alternative protein sources when uncertain about meat quality

The Global Impact: Mad Cow Disease Beyond Borders

While the United Kingdom bore the brunt of the initial BSE crisis, mad cow disease has since been reported in numerous countries worldwide. This global spread has highlighted the interconnected nature of modern agriculture and the importance of international cooperation in disease prevention and control.

Timeline of BSE Emergence

When did mad cow disease first come to prominence? The alarm bells began ringing in 1986 when BSE was first reported among cattle in the UK. The epidemic reached its peak in January 1993, with nearly 1,000 new cases identified per week.

The discovery of a link between BSE and vCJD in 1996 catapulted the issue into the global spotlight, prompting widespread fear and drastic measures to contain the spread of the disease.

Countries Affected by BSE

Which nations have reported cases of mad cow disease? Beyond the UK, BSE has been confirmed in cattle born in numerous European countries, including:

• Austria
• Belgium
• Czech Republic
• Denmark
• Finland
• France
• Germany
• Italy
• Ireland
• Luxembourg
• The Netherlands
• Poland
• Portugal
• Slovakia
• Slovenia
• Spain
• Switzerland

Cases have also been reported in non-European countries such as Canada, Japan, and the United States, albeit in much smaller numbers.

International Response and Cooperation

The global nature of the BSE threat has necessitated unprecedented levels of international collaboration in animal health and food safety. Organizations such as the World Organisation for Animal Health (OIE) and the Food and Agriculture Organization of the United Nations (FAO) have played crucial roles in coordinating efforts to combat the disease.

Key initiatives include:

• Harmonization of BSE surveillance and control measures
• Development of international standards for BSE risk assessment
• Sharing of scientific knowledge and best practices
• Capacity building in developing countries to enhance BSE detection and prevention

The Road Ahead: Ongoing Research and Future Challenges

While significant progress has been made in understanding and controlling mad cow disease, many questions remain unanswered. Ongoing research efforts are focused on several key areas:

Prion Biology and Pathogenesis

Scientists continue to investigate the fundamental mechanisms of prion formation and propagation. Understanding these processes could lead to the development of targeted therapies for prion diseases in both animals and humans.

Improved Diagnostic Tools

Early and accurate diagnosis of BSE and vCJD remains a challenge. Researchers are working on developing more sensitive and specific diagnostic tests, including those that can detect prion infections before the onset of clinical symptoms.

Therapeutic Interventions

The search for effective treatments for prion diseases is ongoing. Potential approaches under investigation include:

• Antibody-based therapies to neutralize prions
• Small molecule compounds to prevent prion aggregation
• Gene therapy to silence prion protein expression
• Stem cell treatments to regenerate damaged neural tissue

Environmental Persistence of Prions

The ability of prions to remain infectious in the environment for extended periods poses unique challenges for disease control. Research into prion decontamination methods and environmental risk factors continues to be a priority.

Zoonotic Potential and Species Barriers

Understanding the factors that allow prions to jump between species is crucial for assessing and mitigating the risk of future outbreaks. Studies on prion adaptation and the molecular basis of species barriers are ongoing.

As our knowledge of prion diseases expands, so too does our ability to combat these devastating conditions. The lessons learned from the mad cow disease crisis have not only improved our understanding of BSE and vCJD but have also revolutionized approaches to food safety and animal health on a global scale.

While the threat of mad cow disease has diminished significantly since its peak in the 1990s, vigilance remains essential. Continued research, stringent regulations, and international cooperation will be key to preventing future outbreaks and protecting both animal and human health in the years to come.

The story of mad cow disease serves as a stark reminder of the complex interplay between agriculture, public health, and scientific discovery. As we face new and emerging threats to global health, the lessons learned from BSE and vCJD will undoubtedly inform our strategies and shape our responses to future challenges in the realm of zoonotic diseases and food safety.

Symptoms, Causes and Treatments for vCJD

Mad cow disease has hit the U.S. and questions about this mysterious disease abound. Here’s what you need to know about mad cow disease.

What Is Mad Cow Disease?

Mad cow disease, or bovine spongiform encephalopathy (BSE), is a transmissible, slowly progressive, degenerative, and fatal disease affecting the central nervous system of adult cattle. The U.S. Department of Agriculture (USDA) has tested hundreds of thousands of cattle for BSE.

Researchers believe that the infectious agent that causes mad cow disease is an abnormal version of a protein normally found on cell surfaces, called a prion. For reasons still unknown, this protein becomes altered and destroys nervous system tissue — the brain and spinal cord.

Does Cooking Food Kill the Prion That Causes Mad Cow Disease?

Common methods to eliminate disease-causing organisms in food, like heat, do not affect prions. Also, prions only seem to live in nervous system tissue.

Does Mad Cow Disease Affect Humans?

A human version of mad cow disease called variant Creutzfeldt-Jakob disease (vCJD) is believed to be caused by eating beef products contaminated with central nervous system tissue, such as brain and spinal cord, from cattle infected with mad cow disease. For this reason, the USDA requires that all brain and spinal cord materials be removed from high-risk cattle — older cattle, animals that are unable to walk, and any animal that shows any signs of a neurological problem. These cow products do not enter the U.S. food supply. The USDA believes this practice effectively safeguards U.S. public health from vCJD.

According to the CDC, four deaths from vCJD have been identified in the U.S. However, it’s believed those cases were caused by consumption of meat outside the U.S.

It is important to clarify the differences between variant CJD and another form of the disease, referred to as classic or sporadic CJD. Classic CJD has no known cause and occurs each year at a rate of one to two cases per 1 million people throughout the world, including in the U. S. and countries where mad cow disease has never occurred. It is not linked to eating nerve tissue from mad cow disease-affected cattle — both vegetarians and meat eaters have died from classic CJD. CJD most commonly affects people over 65 and is usually fatal within six months from onset of symptoms.

What Are the Symptoms of vCJD?

The disease can affect all age groups and is very hard to diagnose until it has nearly run its course. In the early stages of vCJD, people have symptoms related to the nervous system, like depression and loss of coordination. Later in the illness, dementia develops. But only in advanced stages of the disease can brain abnormalities be detected by MRI (magnetic resonance imaging). vCJD is fatal, usually within 13 months of the onset of symptoms.

Is it Possible to Get vCJD From Eating Food Purchased in the U.S.?

It is extremely unlikely that this would happen. To prevent mad cow disease from entering the country, since 1989 the federal government has prohibited the importation of certain types of live animals from countries where mad cow disease is known to exist. This ban includes meat products used in human, animal, and pet foods. In addition, prohibiting high-risk animals from entering the food supply and the removal of central nervous system tissue from the food supply helps assures that BSE is not a risk to consumers.

Can You Get vCJD From Drinking Milk From an Infected Cow?

Milk and milk products are not believed to pose any risk for transmitting mad cow disease to humans. Experiments have shown that milk from mad cow-infected cows has not caused infections.

What About Other Products Made From Cow By-Products?

The FDA stops the importation of cosmetic and dietary supplement ingredients containing bovine materials from animals originating in the 33 countries where mad cow disease has been found or from animals at risk of being infected.

What Is the Current Risk of vCJD to Americans Traveling Abroad?

According to the CDC, the current risk of acquiring vCJD from any specific country appears to be extremely small. But that cannot be precisely determined because cattle products from one country might be distributed and consumed in others.

How Long Have Health Officials Been Concerned About Mad Cow Disease?

Mad cow disease has been of great concern since 1986, when it was first reported among cattle in the U.K. At its peak in January 1993, almost 1,000 new cases per week were identified. Concern about this disease grew significantly in 1996 when an association between mad cow disease and vCJD in humans was discovered.

What Other Countries Have Reported Cases of Mad Cow Disease?

The disease also has been confirmed in cattle born in Austria, Belgium, Czech Republic, Denmark, Finland, France, Germany, Italy, Ireland, Israel, Japan, Liechtenstein, Luxembourg, the Netherlands, Poland, Portugal, Slovakia, Slovenia, Spain, Switzerland, and the U.K.

Canada has also been added to the list of countries from which imports are restricted, although that ban has been lifted recently. Importation of minimal-risk meat products is now allowed from Canada.

Mad Cow Disease | Michigan Medicine

Overview

What is mad cow disease, and does it infect people?

Mad cow disease is a fatal disease that slowly destroys the brain and spinal cord ( central nervous system ) in cattle. It also is known as bovine spongiform encephalopathy, or BSE.

People cannot get mad cow disease. But in rare cases they may get a human form of mad cow disease called variant Creutzfeldt-Jakob disease (vCJD), which is fatal.

This can happen if you eat nerve tissue (the brain and spinal cord) of cattle that were infected with mad cow disease. Over time, vCJD destroys the brain and spinal cord.

There is no evidence that people can get mad cow disease or vCJD from eating muscle meat—which is used for ground beef, roasts, and steaks—or from consuming milk or milk products.

People with vCJD cannot spread it to others through casual contact.

People who have spent a lot of time (at least 3 months) in places where mad cow disease has been found are not allowed to give blood in the United States or Canada. ^{footnote 1footnote 2} This is to help prevent vCJD from spreading.

What causes mad cow disease and variant Creutzfeldt-Jakob disease (vCJD)?

Experts are not sure what causes mad cow disease or vCJD.

The leading theory is that the disease is caused by infectious proteins called prions (say “PREE-ons”). In affected cows, these proteins are found in the brain, spinal cord, and small intestine. There is no proof that prions are found in muscle meat (such as steak) or in milk.

When a cow is slaughtered, parts of it are used for human food and other parts are used in animal feed. If an infected cow is slaughtered and its nerve tissue is used in cattle feed, other cows can become infected.

People can get vCJD if they eat the brain or spinal cord tissue of infected cattle.

How common are mad cow disease and vCJD?

The first case of vCJD was reported in 1996. Since then, there have been a few cases of vCJD reported in the world. Most of the cases have been in countries that are part of the United Kingdom (England, Scotland, Wales, and Northern Ireland).

In December 2003, mad cow disease was discovered in one cow in the United States. Before this cow was found to have the disease, the cow was slaughtered and its muscle meat was sent to be sold in grocery stores. But its organs and nerve tissue were not used for human food. Although mad cow disease cannot be spread through muscle meat, the United States Department of Agriculture (USDA) quickly traced the meat and removed it from grocery stores.

Since 2004, only three more cows in the United States have been found to have mad cow disease. The most recent case of BSE was found in April 2012 in a cow in California.

What are the symptoms of vCJD?

Variant Creutzfeldt-Jakob disease (vCJD) causes the brain to become damaged over time. It is fatal. Symptoms include:

• Tingling, burning, or prickling in the face, hands, feet, and legs. But there are much more common illnesses that cause these same symptoms. Having tingling in parts of your body does not mean you have vCJD.
• Dementia.
• Psychotic behavior.
• Problems moving parts of the body. As the disease gets worse, a person is no longer able to walk.
• Coma.

If a person does eat nerve tissue from an infected cow, he or she may not feel sick right away. The time it takes for symptoms to occur after you’re exposed to the disease is not known for sure, but experts think it is years.

How is vCJD diagnosed?

There is no single test to diagnose vCJD. Doctors may think that a person has vCJD based on where the person has lived and the person’s symptoms and past health. Imaging tests, such as an MRI , may be done to check for brain changes caused by vCJD.

Researchers are now trying to develop a blood test that looks for vCJD. But no blood test is available at this time.

A brain biopsy is the only way to confirm a diagnosis of vCJD.

How is vCJD treated?

There is no cure for vCJD. Treatment includes managing the symptoms that occur as the disease gets worse.

All About BSE (Mad Cow Disease)

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The word BSE is short but it stands for a disease with a long name, bovine spongiform encephalopathy.  “Bovine” means that the disease affects cows, “spongiform” refers to the way the brain from a sick cow looks spongy under a microscope, and “encephalopathy” indicates that it is a disease of the brain. BSE is commonly called “mad cow disease.”

What is BSE?

BSE is a progressive neurologic disease of cows.  Progressive means that it gets worse over time.  Neurologic means that it damages a cow’s central nervous system (brain and spinal cord).

What Causes BSE?

Most scientists think that BSE is caused by a protein called a prion.   For reasons that are not completely understood, the normal prion protein changes into an abnormal prion protein that is harmful.  The body of a sick cow does not even know the abnormal prion is there.  Without knowing it is there, the cow’s body cannot fight off the disease.   

What are the Signs of BSE in Cows?

A common sign of BSE in cows is incoordination. A sick cow has trouble walking and getting up.  A sick cow may also act very nervous or violent, which is why BSE is often called “mad cow disease.”    

It usually takes four to six years from the time a cow is infected with the abnormal prion to when it first shows symptoms of BSE.  This is called the incubation period.  During the incubation period, there is no way to tell that a cow has BSE by looking at it.  Once a cow starts to show symptoms, it gets sicker and sicker until it dies, usually within two weeks to six months.  There is no treatment for BSE and no vaccine to prevent it. 

Currently, there is no reliable way to test for BSE in a live cow.   After a cow dies, scientists can tell if it had BSE by looking at its brain tissue under a microscope and seeing the spongy appearance.  Scientists can also tell if a cow had BSE by using test kits that can detect the abnormal prion in the brain.

Brain from a healthy cow, as seen under a microscope using special stains.

Photo courtesy of Dr. Katie Kelly, Johns Hopkins University

Brain from a cow sick with BSE, as seen under a microscope using special stains. The large white spaces are like the “holes” of a sponge.

Photo courtesy of the late Dr. Al Jenny, USDA

How Does a Cow Get BSE?

The parts of a cow that are not eaten by people are cooked, dried, and ground into a powder. The powder is then used for a variety of purposes, including as an ingredient in animal feed. A cow gets BSE by eating feed contaminated with parts that came from another cow that was sick with BSE. The contaminated feed contains the abnormal prion, and a cow becomes infected with the abnormal prion when it eats the feed.   If a cow gets BSE, it most likely ate the contaminated feed during its first year of life.  Remember, if a cow becomes infected with the abnormal prion when it is one-year-old, it usually will not show signs of BSE until it is five-years-old or older. 

Can People Get BSE?

People can get a version of BSE called variant Creutzfeldt-Jakob disease (vCJD).  As of 2019, 232 people worldwide are known to have become sick with vCJD, and unfortunately, they all have died. It is thought that they got the disease from eating food made from cows sick with BSE. Most of the people who have become sick with vCJD lived in the United Kingdom at some point in their lives. Only four lived in the U.S., and most likely, these four people became infected when they were living or traveling overseas.

Neither vCJD nor BSE is contagious. This means that it is not like catching a cold.  A person (or a cow) cannot catch it from being near a sick person or cow.  Also, research studies have shown that people cannot get BSE from drinking milk or eating dairy products, even if the milk came from a sick cow.

What is the FDA Doing to Keep Your Food Safe?

The U.S. Food and Drug Administration (FDA) is doing many things to keep the food in the U.S. safe for both people and cows.  Since August 1997, the FDA has not allowed most parts from cows and certain other animals to be used to make food that is fed to cows.  This protects healthy cows from getting BSE by making sure that the food they eat is not contaminated with the abnormal prion. 

In April 2009, the FDA took additional steps to make sure the food in the U.S. stays safe.  Certain high-risk cow parts are not allowed to be used to make any animal feed, including pet food.  This prevents all animal feed from being accidentally contaminated with the abnormal prion.  High-risk cow parts are those parts of the cow that have the highest chance of being infected with the abnormal prion, such as the brains and spinal cords from cows that are 30 months of age or older.  

By keeping the food that is fed to cows safe, the FDA is protecting people by making sure that the food they eat comes from healthy cows.

The FDA also works with the U.S. Department of Agriculture (USDA) to keep cows in the U.S. healthy and free of BSE. The USDA prevents high-risk cows and cow products from entering the U.S. from other countries.  The USDA also makes sure that high-risk cow parts, such as the brains and spinal cords, and cows that are unable to walk or that show other signs of disease are not used to make food for people.

The steps the FDA and USDA have taken to prevent cows in the U.S. from getting BSE are working very well.  Only six cows with BSE have been found in the U.S. The first case was reported in 2003 and the most recent case was found in August 2018.

It is worth noting that there are two types of BSE, classical and atypical. Classical is caused by contaminated feed fed to cows. Atypical is rarer and happens spontaneously, usually in cows 8-years-old or older. Of the six U.S. cows found with BSE, five were atypical. The only case of classical BSE in the U.S. was the first one, in 2003, in a cow imported from Canada.

Can Other Animals Get BSE?

Sheep, goats, mink, deer, and elk can get sick with their own versions of BSE.  Cats are the only common household pet known to have a version of BSE.  It is called feline spongiform encephalopathy, and the same things that are being done to protect people and cows are also protecting cats. No cat in the U.S. has ever been found to have this disease.

How Can I Get More Information?

Mad Cow Disease in Humans Symptoms, Causes, Treatment

What Is the History of Where Mad Cow Disease Came From?

In December 2003, the first case of BSE in the United States was detected in a dairy cow in the state of Washington. Two further cases were reported in 2005 and 2006. Before that, a devastating major outbreak occurred in the United Kingdom (England and Ireland) in the 1980s, peaking in 1993. Because the suspected cause was a prion transmitted in meat and bone meal products fed to cattle there, the government banned the practice of feeding such products that may contain diseased tissue to animals in 1988. By then, however, infected cattle had already entered the human food supply. At the peak of this outbreak in 1993, almost 1,000 cases per week of infected cattle were reported; the numbers have dropped dramatically since then, and currently there are only about 10 infected cattle identified each year in the U.K. The BSE-related condition vCJD was first described in the U.K. in 1996. By 1996, several people in the U.K. and others who had lived there were identified with a variant form of CJD (vCJD), and the cause was linked to eating meat from cattle infected with mad cow disease. In June 2014, over 4,000 pounds of beef were recalled by the U.S. Department of Agriculture due to improper processing that allowed cattle brain material (dorsal root ganglia) to be mixed with processed beef.

BSE and resulting cases of vCJD in humans have been diagnosed in other European countries such as Bosnia-Herzegovina, Liechtenstein, Macedonia, Norway, Sweden, and Yugoslavia. According to the World Health Organization (WHO), over 220 cases of vCJD have been reported worldwide, with the majority occurring in the UK (177 cases) and in France (27 cases). Only four cases have been reported in the U.S., and in all four of these cases, there is evidence that indicates that the infection was acquired while abroad in Europe or the Middle East.

Because there is no way to detect BSE in blood, people who have lived for long periods in areas where mad cow disease has been found are not allowed to donate blood in the U.S.

Prion diseases are also known as transmissible spongiform encephaolpathies (TSEs). Overall, prion diseases are a large group of related conditions affecting the nervous system, which affect both animals and humans. Included are Creutzfeldt-Jakob disease (CJD) and variant CJD discussed in detail here in relation to bovine spongiform encephalopathy (BSE, mad cow disease). Another human prion disease is Gerstmann-Sträussler-Scheinker (GSS) disease (see causes below). In animals, chronic wasting disease (CWD) is found in mule deer and elk in the U.S., and scrapie is a similar condition found in sheep. Cases have been reported in the U. S. These diseases all take a long time to develop but are typically rapidly progressive once symptoms begin.

All prion diseases are fatal. Animals and humans who develop a prion disease will die of it. There is no effective treatment. It is important to understand how these diseases are transmitted in order to prevent their spread.

Mad Cow Disease and Variant Creutzfeldt-Jakob Disease

Condition Basics

What is mad cow disease and variant Creutzfeldt-Jakob
disease?

Mad cow disease is a fatal disease that slowly destroys the brain and spinal cord (central nervous system) in cattle. It also is known as bovine spongiform encephalopathy, or BSE.

People cannot get mad cow disease. But in rare cases they may get a human form of mad cow disease called variant Creutzfeldt-Jakob disease (vCJD), which is fatal. Over time, vCJD destroys the brain and spinal cord.

What causes them?

Experts are not sure what causes mad cow disease or variant Creutzfeldt-Jakob disease (vCJD).

The leading theory is that the disease is caused by infectious proteins called prions (say “PREE-ons”). In affected cows, these proteins are found in the brain, spinal cord, and small intestine. There is no proof that prions are found in muscle meat (such as steak) or in milk.

What are the symptoms?

Variant Creutzfeldt-Jakob disease (vCJD) causes the brain to become damaged over time. It is fatal. Symptoms include:

• Tingling, burning, or prickling in the face, hands, feet, and legs. But there are much more common illnesses that cause these same symptoms. Having tingling in parts of your body does not mean you have vCJD.
• Dementia.
• Psychosis.
• Problems moving parts of the body. As the disease gets worse, a person is no longer able to walk.
• Coma.

If a person does eat nerve tissue from an infected cow, he or she may not feel sick right away. The time it takes for symptoms to occur after you’re exposed to the disease is not known for sure, but experts think it is years.

How is variant Creutzfeldt-Jakob disease diagnosed?

There is no single test to diagnose variant Creutzfeldt-Jakob disease (vCJD). Doctors may think that a person has vCJD based on where the person has lived and the person’s symptoms and past health. Imaging tests, such as an MRI, may be done to check for brain changes caused by vCJD.

Researchers are now trying to develop a blood test that looks for vCJD. But no blood test is available at this time.

A brain biopsy is the only way to confirm a diagnosis of vCJD.

How is it treated?

There is no cure for variant Creutzfeldt-Jakob disease (vCJD). Treatment includes managing the symptoms that occur as the disease gets worse.

Where can you get more information?

The following health organizations are tracking and studying mad cow disease and variant Creutzfeldt-Jakob disease (vCJD). Their websites contain the most up-to-date information about these diseases.

• U.S. Centers for Disease Control and Prevention (CDC) provides up-to-date information about mad cow disease and variant Creutzfeldt-Jakob disease (vCJD), including tracking, prevention, travel precautions, and food inspection. You can find information at www.cdc.gov/prions/bse/index.html.
• U.S. Department of Agriculture (USDA) provides information about mad cow disease, the safety of the meat supply in the United States, and infection control guidelines. You can find information at www.fsis.usda.gov/wps/portal/fsis/topics/food-safety-education/get-answers/food-safety-fact-sheets/production-and-inspection/bovine-spongiform-encephalopathy-mad-cow-disease/bse-mad-cow-disease.
• Health Canada answers frequently asked questions about mad cow disease and vCJD and provides information about infection control and food inspection. You can find information at www.phac-aspc.gc.ca/cjd-mcj/index-eng.php.
• The World Health Organization (WHO) website offers information about mad cow disease and vCJD cases around the world and provides infection control guidelines. You can find information at www.who.int/csr/disease/bse/en.

Credits

Current as of:
August 4, 2020

Author: Healthwise Staff
Medical Review:
E. Gregory Thompson MD – Internal Medicine
Adam Husney MD – Family Medicine
Leslie Tengelsen PhD, DVM – Zoonotic Disease

Current as of: August 4, 2020

Author:
Healthwise Staff

Medical Review:E. Gregory Thompson MD – Internal Medicine & Adam Husney MD – Family Medicine & Leslie Tengelsen PhD, DVM – Zoonotic Disease

Is mad cow disease caused by a bacteria?

Transmissible spongioform enchephalopathies (TSE’s), include bovine spongiform encephalopathy (also called BSE or “mad cow disease”), Creutzfeldt-Jakob disease (CJD) in humans, and scrapie in sheep. They remain a mystery, their cause hotly debated. But between 1994 and 1996, 12 people in England came down with CJD, the human form of mad cow, and all had eaten beef from suspect cows. Current mad cow diagnosis lies solely in the detection of late appearing “prions”, an acronym for hypothesized, gene-less, misfolded proteins, somehow claimed to cause the disease. Yet laboratory preparations of prions contain other things, which could include unidentified bacteria or viruses. Furthermore, the rigors of prion purification alone, might, in and of themselves, have killed the causative virus or bacteria. Therefore, even if samples appear to infect animals, it is impossible to prove that prions are causative. Manuelidis found viral-like particles, which even when separated from prions, were responsible for spongiform STE’s. Subsequently, Lasmezas’s study showed that 55% of mice injected with cattle BSE, and who came down with disease, had no detectable prions. Still, incredibly, prions, are held as existing TSE dogma and Heino Dringer, who did pioneer work on their nature, candidly predicts “it will turn out that the prion concept is wrong.” Many animals that die of spongiform TSE’s never show evidence of misfolded proteins, and Dr. Frank Bastian, of Tulane, an authority, thinks the disorder is caused by the bacterial DNA he found in this group of diseases. Recently, Roels and Walravens isolated Mycobacterium bovis it from the brain of a cow with the clinical and histopathological signs of mad cow. Moreover, epidemiologic maps of the origins and peak incidence of BSE in the UK, suggestively match those of England’s areas of highest bovine tuberculosis, the Southwest, where Britain’s mad cow epidemic began. The neurotoxic potential for cow tuberculosis was shown in pre-1960 England, where one quarter of all tuberculous meningitis victims suffered from Mycobacterium bovis infection. And Harley’s study showed pathology identical to “mad cow” from systemic M. bovis in cattle, causing a tuberculous spongiform encephalitis. In addition to M. bovis, Mycobacterium avium subspecies paratuberculosis (fowl tuberculosis) causes Johne’s disease, a problem known and neglected in cattle and sheep for almost a century, and rapidly emerging as the disease of the new millennium. Not only has M. paratuberculosis been found in human Crohn’s disease, but both Crohn’s and Johne’s both cross-react with the antigens of cattle paratuberculosis. Furthermore, central neurologic manifestations of Crohn’s disease are not unknown. There is no known disease which better fits into what is occurring in Mad Cow and the spongiform enchephalopathies than bovine tuberculosis and its blood-brain barrier penetrating, virus-like, cell-wall-deficient forms. It is for these reasons that future research needs to be aimed in this direction.

Creutzfeldt-Jakob disease – Causes – NHS

Types of CJD

The different types of CJD are all caused by a build-up of prions in the brain. But the reason why this happens is different for each type.

Sporadic CJD

Even though sporadic CJD is very rare, it’s the most common type of CJD, accounting for around 8 in every 10 cases.

It’s not known what triggers sporadic CJD, but it may be that a normal prion protein spontaneously changes into a prion, or a normal gene spontaneously changes into a faulty gene that produces prions. 

Sporadic CJD is more likely to occur in people who have specific versions of the prion protein gene.

At present, nothing else has been identified that increases your risk of developing sporadic CJD.

Variant CJD

There’s clear evidence that variant CJD (vCJD) is caused by the same strain of prions that causes bovine spongiform encephalopathy (BSE, or “mad cow” disease).

In 2000, a government inquiry concluded that the prion was spread through cattle that were fed meat-and-bone mix containing traces of infected brains or spinal cords.

The prion then ended up in processed meat products, such as beef burgers, and entered the human food chain.

Strict controls have been in place since 1996 to prevent BSE entering the human food chain, and the use of meat-and-bone mix has been made illegal.

It appears not everyone who’s exposed to BSE-infected meat will go on to develop vCJD.

All definite cases of vCJD occurred in people with a specific version (MM) of the prion protein gene, which affects how the body makes a number of amino acids.

It’s estimated up to 40% of the UK population have this version of the gene.

Cases of vCJD peaked in the year 2000, in which there were 28 deaths from this type of CJD. There were no confirmed deaths in 2014.

Some experts believe that the food controls have worked and further cases of vCJD will continue to decline, but this doesn’t rule out the possibility that other cases may be identified in the future.

It’s also possible for vCJD to be transmitted by blood transfusion, although this is very rare and measures have been put in place to reduce the risk of it happening.

We don’t know how many people in the UK population could develop vCJD in the future and how long it’ll take for symptoms to appear, if they ever will.

A study published in October 2013 that tested random tissue samples suggested around 1 in 2,000 people in the UK population may be infected with vCJD, but show no symptoms to date.

Familial or inherited CJD

Familial or inherited CJD is a rare form of CJD caused by an inherited mutation (abnormality) in the gene that produces the prion protein.

The altered gene seems to produce misfolded prions that cause CJD. Everyone has 2 copies of the prion protein gene, but the mutated gene is dominant.

This means you only need to inherit 1 mutated gene to develop the condition. So if 1 parent has the mutated gene, there’s a 50% chance it will be passed on to their children.

As the symptoms of familial CJD don’t usually begin until a person is in their 50s, many people with the condition are unaware that their children are also at risk of inheriting this condition when they decide to start a family.

Iatrogenic CJD

Iatrogenic CJD (iCJD) is where the infection is spread from someone with CJD through medical or surgical treatment.

Most cases of iatrogenic CJD have occurred through the use of human growth hormone to treat children with restricted growth.

Between 1958 and 1985, thousands of children were treated with the hormone, which at the time was extracted from the pituitary glands (a gland at the base of the skull) of human corpses.

A minority of those children developed CJD, as the hormones they received were taken from glands infected with CJD.

Since 1985, all human growth hormone in the UK has been artificially manufactured, so there’s now no risk.

But a small number of people exposed before 1985 are still developing iCJD.

A few other cases of iCJD have occurred after people received transplants of infected dura (tissue that covers the brain) or came into contact with surgical instruments that were contaminated with CJD.

This happened because prions are tougher than viruses or bacteria, so the normal process of sterilising surgical instruments had no effect.

Once the risk was recognised, the Department of Health tightened the guidelines on organ donation and the reuse of surgical equipment. As a result, cases of iCJD are now very rare.

BSE (‘mad cow’ disease)

Bovine spongiform encephalopathy (BSE), also known as “mad cow” disease, is a relatively new disease that first occurred in the UK during the 1980s.

One theory about why BSE developed is that an older prion disease that affects sheep, called scrapie, may have mutated. 

The mutated disease may have then spread to cows that were fed meat-and-bone mix from sheep containing traces of this new mutated prion.

Is CJD contagious?

In theory, CJD can be transmitted from an affected person to others, but only through an injection or consuming infected brain or nervous tissue.

There’s no evidence that sporadic CJD is spread through ordinary day-to-day contact with those affected or by airborne droplets, blood or sexual contact. 

But in the UK, variant CJD has been transmitted on 4 occasions by blood transfusion.

90,000 Neuroscientists prevent the transformation of prions into pathogenic form for the first time

NIAID / Flickr

For the first time, neuroscientists have accurately determined the transitional conformations of the process of transformation of normal prion proteins into a pathological form.Scientists were also able to stop this process in the Petri dish using antibodies directed at the identified area of ​​the protein, from which the misfolding begins. This discovery paves the way for potential treatments for prion diseases. Article published in Proceedings of the National Academy of Sciences .

Prions are proteinaceous infectious agents coiled into a pathogenic form. Prions can initiate abnormal curling of other normal-shaped proteins they encounter.They cause a cascade of irregular convolution, form clusters and deform the cells in which they are located. Usually prions infect brain cells and cause irreversible damage in it.

The most famous prion diseases are Creutzfeldt-Jakob disease, kuru cannibal disease (“laughing death”), Gerstmann-Straussler-Scheinker syndrome, which affect humans, as well as bovine spongiform encephalopathy (“mad cow disease”) and sheep pruritus … All these diseases are neurodegenerative in nature, incurable and lead to death.

Prion diseases usually develop spontaneously and are associated with hereditary genetic mutations. In rare cases, prion proteins can be passed on through food, blood, or surgical instruments. In their healthy form, prion proteins are involved in the maintenance of myelin on peripheral nerves, as well as in calcium modulation, copper uptake, and long-term potentiation. While both the normal and pathogenic versions of the prion protein have already been described in detail, the intermediate stage of transformation has remained unexplored due to the instability of the transitional form of coagulation, which created barriers to studying its molecular structure.

A research team from Imperial College London led by Professor Máximo Sanz-Hernández studied this intermediate conformation of the protein molecule and found a place in the prion structure where it began to fold into a pathogenic form. The team worked with a mutant version of the prion protein T183A huPrP , which is found in people with hereditary prion diseases. Using nuclear magnetic resonance spectroscopy in combination with computational analysis, the researchers identified the locations of the protein molecule where conformational changes occur, as well as possible transitional conformations of the molecule.

It turned out that a mutation in the genetic sequence of carriers of hereditary prion diseases causes a slight violation of the secondary structure of the protein. This change destabilizes the protein and provokes a conformational transition between the normal and intermediate forms of the molecule. Modeling the dynamics of possible conformational transitions of the prion molecule showed that the mutant version of the protein under physiological conditions tends to accumulate in the pathogenic form T183A huPrP ^Sc .

To confirm the key role of protein intermediate conformation in the misfolding process, Maximo Sans-Hernandez’s team used monoclonal antibody POM Abs , produced by a team at the University of Zurich. These antibodies specifically bound to prion proteins in the normal conformation huPrP ^C , blocking their transition to the intermediate conformation. As a result, using antibodies, it was possible to completely prevent the formation of the pathogenic conformation of prion huPrP ^Sc in a Petri dish.

The mechanism of blocking the formation of an intermediate form of a mutant protein by POM1 antibodies, which prevented the formation of pathogenic prions T183A huPrP *

Máximo Sanz-Hernández et al. / PNAS, 2021

Despite the fact that in their current form, the antibodies used are too large in size to pass into the brain, this is the first study to demonstrate that it is in principle possible to disrupt the mechanism of formation of a pathological form of prions.The details of the molecular transformations of prions discovered by Maximo Sans-Hernandez and his team will help advance the development of drugs against deadly diseases associated with them.

Previously, scientists were able to successfully slow down the course of prion scrapie disease in mice using targeted antisense therapy – a method of blocking protein synthesis at the stage of messenger RNA.

Ilya Gridnev

90,000 Brain parasites: scientists have found new evidence of the danger of prions

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Brain parasites: scientists have found new evidence of the danger of prions

Brain parasites: scientists have found new evidence of the danger of prions – RIA Novosti, 17.01.2019

Brain parasites: scientists have found new evidence of the danger of prions

Most cases of mad cow disease in humans have been identified in the UK. Some of the British, scientists believe, are genetically predisposed to this disease … RIA Novosti, 17.01.2019

2019-01-17T08: 00

2019-01-17T08: 00

2019-01-17T11: 22

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MOSCOW, 17 Jan – RIA Novosti, Tatiana Pichugina. Most cases of mad cow disease in humans are found in the UK. Some of the British, scientists believe, are genetically predisposed to this disease. It is believed to be caused by prions, which are structurally disturbed proteins that act like an infection. Despite serious research, the nature of prions is still unclear. Europe is scared In 1995 in the UK, two adolescents were diagnosed with a very rare form of spongiform encephalopathy, or Creutzfeldt-Jakob disease.In March 1996, ten cases were already recorded. The patients suffered from pain, mental and neurodegenerative disorders, and soon died. The disease was associated with the spread of a new form of mad cow disease – an infectious disease that affects cattle, sheep, and deer. Speculation about whether the virus can be transmitted from pets to humans has been around for a long time. Laboratory experiments have shown that there is an interspecies barrier preventing this, however, judging by the outbreak of the mid-1990s, this was not enough.The spread of the disease caused a wide public outcry in the world, talking about the health crisis in the European Union and the gap in knowledge regarding the causes of mad cow disease. Large-scale research began, but even thirty years later, scientists cannot clearly answer the key question – what are the risks of contracting prion diseases when eating meat from raised animals. Terrible prions Proteins are the main building blocks of living organisms. They are synthesized in cells according to the information contained in the DNA.In order to perform their functions, protein molecules are curled and packaged in a certain way. Violation of these processes poisons the body and can cause disease. A class of such pathogenic proteins, for the synthesis of which errors in the PRNP gene are responsible, are called prions. According to one of the most common hypotheses, it is prions that cause various forms of spongiform encephalopathy in animals and humans. They are able to infect healthy proteins and multiply using a kind of “seeds” of polymer chains. Due to their irregular structure, they stick together and form plaques in the brain, disrupting the functioning of neurons.As a result, the brain gradually stops working normally and dies. Prion diseases are very rare in humans. Today, 231 cases are known in the world, and 178 of them are among the residents of Great Britain. After the peak of 2001-2002, their number is decreasing. The patients were found to have a mutation in the 129th codon of the 20th chromosome, which indicates a genetic predisposition to this disease. There is evidence that one in two thousand in the UK population has this mutation. Scientists believe that these people can suddenly develop the disease after seven to ten years of the incubation period.Or its carriers may never get sick, but infect others through donation of blood and organs, such as the retina. This route of spread of the disease is now being actively studied. Aging and improper proteins In recent years, new forms of prion diseases have been discovered in animals and humans. For example, they have been identified in camels and cats, and have proven that they can be infected with monkeys. In 1992, the prion nature of a very rare hereditary disease – fatal familial insomnia – was discovered. The disease manifests itself in adults, a person loses sleep, sees hallucinations, and then dies.The reason is also a mutation in the PRNP gene, which turns a normal protein into a prion. Scientists have found that the protein for which the PRNP gene is responsible has several forms, only one of which is toxic. Experiments on mice have shown that normal prions appear already in the brain of the embryo and accompany it during development. In adults, they are found in the heart and skeletal muscles, in immune cells. Good prions play a role in cell affinity, signal transduction across cell membranes, and in the metabolism of copper ions, possibly serving as neuroprotective agents.Incorrectly structured proteins (beta-amyloids) accompany incurable age-related disorders, including Alzheimer’s, Parkinson’s, Huntington’s, dementia. Recently, scientists have begun to seriously consider the hypothesis that beta-amyloids accumulate and spread in the body as well as pathogenic prions. Despite active searches, it is still not known why prions and beta-amyloids arise in the body, they are the cause of brain disorders, or vice versa. The diseases associated with them are still incurable.

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MOSCOW, 17 January – RIA Novosti, Tatyana Pichugina. Most cases of mad cow disease in humans have been reported in the UK.Some of the British, scientists believe, are genetically predisposed to this disease. It is believed to be caused by prions, which are structurally disturbed proteins that act like an infection. Despite serious research, the nature of prions is still unclear.

Europe is scared

In 1995 in the UK, two adolescents were diagnosed with a very rare form of spongiform encephalopathy, or Creutzfeldt-Jakob disease. In March 1996, ten cases were already recorded.The patients suffered from pain, mental and neurodegenerative disorders, and soon died.

The disease was associated with the spread of a new form of mad cow disease – an infectious disease that affects cattle, sheep, and deer. Speculation about whether the virus can be transmitted from pets to humans has been around for a long time. Laboratory experiments have shown that there is an interspecies barrier preventing this, however, judging by the outbreak of the mid-1990s, this was not enough.

The spread of the disease caused a wide public outcry in the world, talking about the health crisis in the European Union and the gap in knowledge regarding the causes of mad cow disease.Large-scale studies began, but thirty years later, scientists cannot clearly answer the key question – what are the risks of contracting prion diseases when eating meat from raised animals.

23 November 2018, 07:09 They are synthesized in cells according to the information contained in the DNA. In order to perform their functions, protein molecules are curled and packaged in a certain way.Violation of these processes poisons the body and can cause disease. A class of such pathogenic proteins, for the synthesis of which errors in the PRNP gene are responsible, are called prions.

According to one of the most common hypotheses, it is prions that cause various forms of spongiform encephalopathy in animals and humans. They are able to infect healthy proteins and multiply using a kind of “seeds” of polymer chains. Due to their irregular structure, they stick together and form plaques in the brain, disrupting the functioning of neurons.As a result, the brain gradually stops working normally and dies. Prion diseases are very rare in humans. Today, 231 cases are known in the world, and 178 of them are among the residents of Great Britain. After the peak of 2001-2002, their number is decreasing.

The patients were found to have a mutation in the 129th codon of the 20th chromosome, which indicates a genetic predisposition to this disease. There is evidence that one in two thousand in the UK population has this mutation. Scientists believe that these people can suddenly develop the disease after seven to ten years of the incubation period.Or its carriers may never get sick, but infect others through donation of blood and organs, such as the retina. This route of spread of the disease is now being actively studied.

Aging and malformed proteins

In recent years, new forms of prion diseases have been discovered in animals and humans. For example, they have been identified in camels and cats, and have proven that they can be infected with monkeys.

In 1992, the prion nature of a very rare hereditary disease – fatal familial insomnia – was discovered.The disease manifests itself in adults, a person loses sleep, sees hallucinations, and then dies. The reason is also a mutation in the PRNP gene, which turns a normal protein into a prion.

Scientists have found that the protein for which the PRNP gene is responsible has several forms, only one of which is toxic. Experiments on mice have shown that normal prions appear already in the brain of the embryo and accompany it during development. In adults, they are found in the heart and skeletal muscles, in immune cells.

Good prions play a role in cell affinity, signal transduction across cell membranes, and in the metabolism of copper ions, possibly as neuroprotective agents.

Proteins of irregular structure (beta-amyloids) accompany incurable age-related disorders, including Alzheimer’s, Parkinson’s, Huntington’s, dementia. Recently, scientists have begun to seriously consider the hypothesis that beta-amyloids accumulate and spread in the body as well as pathogenic prions.

Despite active searches, it is still not known why prions and beta-amyloids appear in the body, they are the cause of brain malfunction, or vice versa.The diseases associated with them are still incurable.

13 January 2017, 13:06

Mad cow disease and prion diseases

I.A. Zavalishin
Professor, Doctor of Medical Sciences
I.E. Shitikova
Candidate of Medical Sciences
Scientific Center of Neurology, Russian Academy of Medical Sciences

Prion diseases are a group of neurodegenerative diseases in humans and animals, etiologically associated with a special infectious protein – prion.These diseases are characterized by a severe progressive course and inevitable death.

About 10 years ago, interest in prion diseases in the world sharply increased due to the registration of a new, especially severe and early variant of Creutzfeldt-Jakob disease, which appeared during the epidemic of the so-called bovine spongiform encephalopathy in England. The maximum incidence of animals – up to 37 thousand heads – fell on 1992. In total, over the period from 1985 to 1996, 170 thousand head of livestock were affected.In addition, during the same period, besides cows, spongiform encephalopathy was reported in five species of London Zoo antelopes, domestic cats, other animals and cows outside Britain.

In the spring of 1996, the registration of a new variant of the previously known but extremely rare Creutzfeldt-Jakob disease (the incidence in the world is 1 case per 1 million people per year) and the associated “mad cow disease” literally shook the economic and political circles of England. This variant of the disease appeared in 1995, with individual cases reported in France and Italy.The disease made its debut at a young age, which is atypical for this disease, known since the 1920s, and in the process of morphological examination of the brain of deceased patients, changes were revealed similar to those in bovine spongiform encephalopathy.

And now a little history …
For the first time the term “spongy (spongy, spongy) encephalopathy” was used in 1957 by the Icelandic scientist B. Sigurdsson when describing diseases of sheep on the island of Iceland, which differed from all known diseases by four signs: unusually long (up to several years) incubation period; slowly progressing (months and years) nature of the course; unusual damage to organs and tissues; inevitable death.B. Sigurdsson united such diseases under the general name “slow infections”.

Three years later, kuru was described for the first time – a previously unknown disease that occurs among savages with the habits of ritual cannibalism on the island of New Guinea, manifested by impaired coordination of movements and tremors. The clinical and pathological symptoms of kuru in humans were similar to those in sheep’s disease, known since 1700 – scrapie. In 1966, Gaidushek proved the infectious nature of kuru on monkeys (chimpanzees).In 1967, researchers published data according to which the following were found in the brain of chimpanzee chimpanzees infected with the kuru virus: “sponginess” of the gray matter of the brain, an increase in the number of auxiliary cells (astroglia), the death of neurons in several parts of the brain. These morphological signs (with certain variations) are characteristic of all prion diseases of humans and animals.

Subsequently, spongiform encephalopathy was discovered in people suffering from Creutzfeldt-Jakob disease, Gerstmann-Streussler syndrome, and fatal familial insomnia.At the end of the last century, WHO experts predicted the possibility of a significant epidemic of a new variant of Creutzfeldt-Jakob disease in the next 10 years. But in the last 5 years, fortunately, there has been a clear tendency towards a decrease in the increase in the disease.

By 2005, however, about 140 cases of the new variant of Creutzfeldt-Jakob disease had been reported in England, France and Italy. The disease is characterized by an earlier than usual onset. The age of the patients varied from 16 to 40 years, at the onset of the disease, mental disorders in the form of anxiety, depression, and changes in behavior were noted as clinical manifestations; after weeks and months, neurological disorders were added.In the later stages, as in other prion diseases, memory impairment, dementia, muscle twitching, increased muscle tone; the disease ends in death within 0.5-2 years. In Russia, there is no data on the emergence of a new variant of Creutzfeld-Jakob disease, although the usual Creutzfeld-Jakob disease with late onset of symptoms occurs with the same frequency as in other countries.

A big mystery and, accordingly, of interest is the fact that some variants of prion diseases can be infectious in nature (for example, caused by a dura mater transplant or the use of tissue extracts containing growth hormone and gonadotropin), others are hereditary, and still others are in no way related to either heredity or infectious transmission.

In all cases, the culprit of the disease is its own defective protein – prion protein, which turns into an infectious analogue – prion. The prion, as it were, “forces” the surrounding normal prion protein molecules to take a pathological form, and this process has the character of a chain reaction. As Professor Stanley Prusiner aptly put it, “Dr. Jekyll is turning into Mr. Hyde.” A defective prion protein has abnormal properties and is contagious and fatal to any nearby neurons.

Professor S. Pruziner received the 1997 Nobel Prize in Physiology or Medicine for his proof of the existence of a new biological infectious agent – a prion that does not contain DNA or RNA, capable of carrying information and crossing the species barrier.

Currently, the diagnostic criteria for prion diseases have been unified, and work is underway to identify and study them. The advances in molecular biology in recent years give hope for a deeper understanding of the cause of the disease and the mechanisms of pathological transformation of the prion protein, and, most importantly, for finding effective means to treat these deadly diseases.The preliminary results of experimental studies on cell cultures are very encouraging, and it is possible that some “anti-prion” compounds may become the object of the first clinical trials in the next 5 years.

© The Nerves magazine, 2007, # 2

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Prion diseases – new data / Jeep Treo | Scientific discoveries and technical innovations from Germany | DW

More recently, newspapers, radio and television spoke about mad cow disease in cattle and the so-called new form of Kreuzfeldt-Jakob disease in humans, which is believed to be associated with eating the meat of infected animals.Experts predicted a massive epidemic comparable in scale to the AIDS epidemic, and perhaps even more dire in consequences. Since then, this topic has gradually disappeared, although there are no objective grounds for this: from time to time, in one or another European country, a sick animal is found, and a new form of Kreuzfeldt-Jakob disease has already claimed the lives of 140 people … However, the lack of hype in the media does not mean that scientists have lost interest in the problem.On the contrary, research is in full swing and is yielding very interesting results. Before talking about them, I will briefly recall what these neurodegenerative diseases are, leading to the gradual destruction of the brain and death. Their main feature is that they are not caused by traditional pathogens – bacteria, fungi or viruses – but by the so-called prions, that is, infectious proteins. These abnormal proteins, having the same amino acid composition as the normal ones that are constantly present in a healthy body, differ from them only in that their molecules have a different spatial organization.When infectious prions enter the body, a kind of chain reaction begins, during which normal prions are transformed into abnormal ones. It is believed that the now banned practice of using meat and bone meal as a protein supplement for cattle feed, which may well have contained the remains of sick animals, caused the mad cow disease epidemic. And the consumption of meat – primarily the brain and entrails – of infected cows is fraught with a new form of Kreuzfeldt-Jakob disease for humans.Professor Adriano Aguzzi, head of the laboratory for the study of prion diseases at the Institute of Neuropathology at the University of Zurich, one of the leading experts in this field not only in Switzerland, but worldwide, says:

For many years now my laboratory studies the ways of propagation of prion infection in the body from the periphery to the brain.

Aguzzi better than anyone else imagine what kind of destruction this terrible infection causes in the brain of patients:

This idea alone makes me lose my appetite.

The scientist believes that not everyone has fully realized the danger looming over humanity:

Mad cow disease marks probably the most serious crisis caused by an error in assessing the consequences of the introduction of new technologies over the past 50 years. This is not just another crisis – this is an unprecedented catastrophe.

It is all the more important to find out how the spread of prion infection in the body occurs. Aguzzi and his colleagues set out to trace all the stages on the path of prions from the stomach, where they get with the meat of infected animals, to the brain, where they cause fatal destruction of the nervous tissue.According to the scientist, the patient’s own immune system not only does not suppress the infection, but plays an important role in its spread: having overcome the stomach wall, prions accumulate in special immune cells:

There are so-called follicular dendritic cells – they are located in the lymph glands and in the spleen, and in the tonsils, and around the intestines. Well, these cells accumulate abnormal prions like a sponge.

And then what? Scientists have found the answer to this question only a few days ago:

As a result of many years of research, we managed to find out that the pathogen first accumulates in the lymph glands and multiplies there.But until now it was not clear what happens next: the lymph glands are not directly connected with the nervous system. However, there are peripheral, so-called sympathetic nerve endings – there is nothing nice about them in this case – that penetrate both the lymph glands and the spleen.

Through these nerve endings, prions enter the brain. However, if their penetration from the stomach into the lymphatic system occurs quickly, then for months, or even years, practically nothing happens at all.According to Aguzzi, the fact is that prions simply cannot cover the distance separating immune cells from nerve cells:

We performed such a manipulation, as a result of which the distance between follicular dendritic cells and nerve cells decreased. Using genetic engineering techniques, we brought follicular dendritic cells closer to nerve cells, and then artificially infected mice with pathogenic prions, and it turned out that now the infection spreads much faster.From this, we concluded that the distance between the nerves and follicular dendritic cells is the limiting factor that determines the speed of the process of damage to the nervous system.

In the case of mice, the rapid spread of infection means that the prions do not reach the nervous system 8 months after infection, but only one month later. At the same time, the distance between follicular dendritic cells and nerve endings decreased by only a few tenths of a millimeter.In humans, the count must go, apparently, by millimeters, which, perhaps, explains the extremely long incubation period.

Today we proceed from the assumption that after prions enter the body, it takes years before they reach the brain. Therefore, it is extremely important for us to know all these relationships in detail in order to understand whether we can do something to prevent the disease in an already infected person. This, in fact, is the purpose of all our research!

In the meantime, Aguzzi is trying to understand the mechanism of overcoming this critical distance by prions.Either some unknown substances-mediators play a role here, or some mediator cells help. As part of these studies, Swiss scientists have already managed to significantly increase the sensitivity of tests for infectious prions. Aguzzi and his colleagues have developed biochemical methods that artificially increase the concentration of prions in a sample. This increased the sensitivity of the tests by several thousand times. Scientists used their development to analyze tissue samples from 36 patients who died between 1996 and 2002 from the so-called classic form of Creutzfeldt-Jakob disease, which affects an average of one in a million elderly people aged 60-65. years:

And it turned out that if you carefully examine tissue samples using the most sensitive methods of analysis, then in almost a third of cases of sporadic Creutzfeldt-Jakob disease, abnormal prions are found in the spleen and in another third of cases in skeletal muscles.

So, in ten out of 36 patients, prions were found in the spleen, in eight – in muscle tissue, in three – both there and there. True, the concentration of these proteins in peripheral organs turned out to be about a thousand times less than in the brain. It seems that the new form of Creutzfeldt-Jakob disease also differs from the classical one in the way that the infection does in the body: in the first case, abnormal prions from the stomach through the lymphatic system enter the nervous system and affect the brain, in the second case, abnormal prions, transforming from normal prions in the brain are now found to spread throughout the body.A number of conclusions follow from this. For example, this: not only neurosurgeons, but also general surgeons should pay increased attention to the problem of sterilizing instruments in order to prevent accidental transmission of infection. Another conclusion is the possibility of creating a reliable intravital diagnosis of prion diseases based on biopsy of muscle tissue or lymph nodes. Using highly sensitive methods of analysis, Professor Aguzzi intends to find out how many people are infected with prions from “mad cows”:

Today, Switzerland has three times the incidence of Creutzfeldt-Jakob disease than any other country in the world.And we do not understand what lies behind this phenomenon – whether mad cow disease, or something else – but we are very alarmed. And I need to know how many people in Switzerland are actually infected: say, 3 people or 5 percent of the population – this is a huge difference. But the fact of the matter is that we do not know this. Therefore, we have now begun collecting and examining tonsil tissue samples from all tonsillectomy surgeries performed in Switzerland.

By themselves, the tonsils are not directly related to Creutzfeldt-Jakob disease, however, the sensitive method of analysis developed by Aguzzi made it possible to detect infectious prions in patients who died from this disease, and therefore tissue samples from a large number of people will make it possible to realistically assess the probability mass epidemic.However, Professor Aguzzi emphasizes that this method is not suitable for a large-scale examination of cows:

It cannot be automated. It is already very sensitive, but we have one technician who needs 2 full working days to process a dozen samples. It is clear that testing tens of thousands of cows in this way is a completely unrealistic task.

At the same time, early diagnosis is extremely important, since only it will allow, possibly, to stop the spread of prions in the body.According to Aguzzi, if the disease has somehow manifested itself, it’s too late to do anything:

After that, no effective therapy is possible, too much tissue is destroyed. Something else can be done as long as there are no clinical symptoms.

However, today Aguzzi is no longer so categorical. He was forced to reconsider his views by the results of a study by British scientists published the other day. Until now, doctors imagined the mechanism of brain tissue degeneration as follows: due to their abnormal spatial structure, infectious prions are perceived by the cell as something foreign, the cell inactivates these proteins, they become insoluble and form some threads or lumps that no longer have any function, they simply fill the cell space.And these non-functional proteins, accumulating, kill the cell. That is, ulceration of the brain tissue, its transformation into a kind of sponge – that’s why the disease is called “spongiform encephalopathy” – can be considered a kind of consequence of the accumulation of protein waste, and this process is irreversible. But Dr. Giovanna Mallucci of King’s College London questioned this hypothesis. She modified the genome of the experimental mice, as if having built a timer into it so that normal prions were synthesized in the body of these transgenic animals not throughout their lives, but only up to 12 weeks of age.

We infected these mice shortly after they were born. As long as there were healthy prion proteins in their nervous system, the disease developed as usual: inflammation grew, abnormal proteins clumped together, forming shapeless lumps, and were deposited in the cells of the brain tissue, typical holes appeared in the brain. But when healthy prions disappeared from the nervous system, the experimental mice not only did not die within the next two weeks, as happened with the animals from the control group, but, on the contrary, recovered: the development of the disease stopped and even reversed, the brain tissue gradually recovered, no holes became.

Professor Aguzzi does not hide his admiration for the work of a colleague:

The experiments she conducted are truly brilliant, truly fantastic work. Just unbelieveble! First of all, I was surprised that the symptoms that had already taken place disappeared. This is amazing. And secondly, this means that if you turn off the synthesis of normal prions, then the abnormal ones are powerless to cause damage to the body. And this is already a very, very promising start.

Abnormal prions continue to accumulate in the brains of transgenic mice, but no longer lead to fatal consequences typical of this disease.Giovanna Mallucci says:

This means that the poison for nerve cells is not the infectious prions themselves, but only the process of converting normal prions into abnormal ones. It is this process of protein transformation that destroys brain tissue.

So specialists working on the creation of drugs for the treatment of prion diseases and directing all their efforts to find ways to remove accumulations of infectious prions from the brain should take a closer look at healthy prions, especially since it is still unknown what function they perform in the body.But one way or another, Professor Aguzzi is sure:

Mad cow disease will keep us occupied for many years to come, we cannot get rid of it so quickly. Unfortunately, this is the reality.

Automotive heading

An unusual conceptual development was demonstrated at the auto show in Tokyo by the American company “Jeep”. The Jeep Treo represents a new stage in the development of conceptual urban mobile vehicles developed by DaimlerChrysler.

The novelty is intended for young active townspeople and destroys all ideas related to the size and maneuverability of Jeep cars. After all, “Treo” has rather modest dimensions – its length is a little more than three meters, and its width and height are a little more than one and a half meters. The novelty is designed for three passengers, and although the car looks small outwardly, the interior is very spacious and comfortable.

The Treo has two high-mounted spar fenders at the rear.They have red parking lights and a very handy mountain bike rack. The tailgate opens like a hatchback and provides easy access to the trunk.

Only the branded radiator grille gives out the Jeep brand.

The fact is that the designers decided to look at the traditional elements of the brand in a new way. An example is a disproportionately wide, convex windshield. It creates a spacious feeling, which is enhanced by the glass roof over the head of the rear passenger.

The Jeep Treo salon is simple and convenient – the steering column, pedals, speedometer and other instruments are made in one module, which can be instantly rebuilt for “right” or “left” steering wheel. It is also unusual that this particular module, and not the seat, is adjusted to the dimensions of a particular driver. The second – removable – module contains a satellite navigation system, a touch screen and climate control.

The lightweight seats are made of a translucent carbon fiber frame, and the rear seats can be folded down completely flat.Another feature of the car is the 19-inch wheels, which are strongly removed from the body.

Permanent all-wheel drive of the novelty is provided by a hybrid power plant with two electric motors for the front and rear axles. Electricity is provided by a fuel cell that does not emit harmful gases.

According to representatives of the DaimlerChrysler concern, there is no question of mass production of the car. The Jeep Treo is a purely conceptual development for testing new technological solutions that may soon appear on production models.

Spongiform encephalopathy: prions and viruses in one team | Scientific discoveries and technical innovations from Germany | DW

A person has many enemies, but the most dangerous and merciless of them are so small that they cannot be seen with the naked eye. These are pathogenic microorganisms. Everyone knows about pathogenic bacteria, protozoa and viruses. And the fact that fungal infections – mycoses – can be just as dangerous for human health and even life, were probably heard by many, especially since bacteria, viruses and fungi as causative agents of diseases have been known for a very long time.However, there is a very special, extremely unusual class of pathogens, the very existence of which no one even suspected two decades ago.

We are talking about prions – anomalous infectious proteins, for the discovery of which the American Stanley Prusiner was awarded the Nobel Prize in 1997. Prions cause in animals and humans severe, currently incurable diseases of the central nervous system – spongiform encephalopathy. Mad cow disease in cattle, scrapie in sheep and goats, a number of similar diseases in cats and rodents, as well as kuru and Kreuzfeldt-Jakob syndrome in humans – all these are, albeit different, but closely related neurodegenerative diseases caused by prions.

“Slow viruses” turned out to be pathogenic proteins

For a long time it was believed that the causative agents of these diseases are viruses, and since the incubation period of such diseases is calculated in years, these hypothetical viruses were called slow. But the “slow viruses” had other features as well. So, if ordinary viral infections cause the body’s immune response (inflammation, fever, production of antibodies and interferon), then the body did not react to “slow viruses”.In addition, all known viruses consist of a nucleic acid (DNA or RNA) enclosed in a protein membrane, and it is possible to destroy nucleic acid and thereby inactivate viruses by boiling, exposure to formaldehyde, ultraviolet or ionizing radiation, but in the fight against “slow viruses” all these funds proved to be ineffective. Finally, ordinary viruses, although extremely small, are still visible through an electron microscope. But scientists could not identify or even discern “slow viruses”.Instead, they found infectious proteins.

Protein molecules are characterized by primary, secondary, tertiary, and sometimes quaternary structures. The primary structure reflects the sequence of amino acid residues that make up this molecule. Secondary structure is a conformation, a way of twisting a molecule in space (for example, a spiral). Tertiary structure is the spatial configuration of an already twisted molecule (say, the same spiral, but also curved). Well, a quaternary structure can be formed due to the interaction between molecules, it is characteristic only of some proteins, for example, hemoglobin.

A change in conformation makes a protein pathogenic and infectious

Each protein has its own unchanged structure, by which the cell identifies it. A protein with a structure unfamiliar to the cell is foreign to it and is subject to inactivation. So, it turned out that in the body of all mammals, including humans, there is a certain group of proteins that can exist in two forms – normal and abnormal. While such a protein is in its normal form (it is called the alpha conformation), it dissolves well in biological fluids and is able to perform its proper function.

So far, however, scientists do not know which one. However, occasionally this protein, for some unknown reason, takes an abnormal shape – it is called the beta conformation. This “wrong” protein is called a prion. That is, it is the body’s own protein, which has acquired pathogenic properties due to a change in conformation. Actually, both the alpha and beta conformation of the prion protein is a helix, but the abnormal protein molecule has about 10 percent fewer bent regions than the normal protein molecule.As a result, the abnormal protein forms insoluble aggregates that only fill the cell space, but do not perform any functions.

Accumulating, these harmful proteins destroy the nervous system of the body over time. But prions are not only pathogenic, but also infectious proteins: when faced with their normal counterparts, they transform them into their own conformation, as it were, infect. Prions behave in the same way in a foreign organism: once in a foreign organism, they can cause the appearance of beta-conformations of normal proteins encoded by the same gene as themselves.And this process is practically irreversible.

Prion infection activates endogenous retroviruses

Much in this picture still requires in-depth research, but the prion nature of spongiform encephalopathy itself is not in doubt today. Scientists at the Leibniz Institute for Animal Research in Zoos and Wildlife in Berlin do not dispute it either. However, they believe that viruses are also involved in the development of this disease, but not those that attack the body from the outside, but those that are already integrated into it.These are the so-called endogenous retroviruses. Once introduced in the process of evolution into the organism of an animal or a person, they forever remained in the DNA of its cells and turned into a new genetic element of its genome.

Most of these inclusions do not perform any function – at least these functions are unknown to science – and form what is often called useless, or junk DNA. Professor Alex Greenwood, an American virologist at the Berlin Zoo and Wildlife Research Institute, explains: “Endogenous retroviruses account for up to ten percent of the hereditary material in mammals.If we bear in mind that the actual human genes make up only 2-3 percent of the genome, we can say that we are not so much humans as viruses. ”

In experiments on mice, Professor Greenwood and his colleagues found that the increased activity of endogenous retroviruses in the genome causes symptoms similar to those of spongiform encephalopathy. To test the hypothesis of such a relationship, the Berlin researchers contacted the staff of the German Primate Center in Göttingen, which is studying Creutzfeldt-Jakob disease in macaques.”We compared the activity of genes in the brains of healthy animals and animals infected with prions,” says Professor Greenwood.

Today, spongiform encephalopathy is considered incurable, since doctors do not have any means of fighting prions. But if endogenous viruses do play a key role in the development of this disease, this could make a difference, since drugs that effectively suppress retroviruses already exist.

Author: Vladimir Fradkin
Editor: Efim Shuman

How to detect a hidden threat – analytical portal POLIT.RU

Two groups of researchers have proposed an effective method for detecting asymptomatic carriers of prion diseases by blood analysis.

The epidemic of mad cow disease (bovine spongiform encephalopathy) has caused more than two hundred deaths in Europe. Proteins of an abnormal shape (prions) responsible for this disease, entering the human body with cow meat, cause a similar disease in him (Creutzfeldt-Jakob disease).Doctors cannot save a person from illness. As a rule, after the first symptoms of the disease appear (progressive dementia, hallucinations, epileptic seizures), the patient does not live for 13-14 months. More details about mad cow disease, Creutzfeldt-Jakob disease and other diseases of this type can be found in the special essay “How to Uncover the Secrets of Prions”.

It is also known that prions can be in the body for a long time while the symptoms of the disease have not yet appeared. The duration of the asymptomatic period is unpredictable, with a maximum recorded period of 50 years.Therefore, thousands of Europeans may be carriers of Creutzfeldt-Jakob disease. In 2004, it was finally proved that such people can transmit the disease to others through donated blood. Examination of tissue from removed appendixes and tonsils shows that in the UK, abnormal proteins are present in one in two thousand people. Four cases of infection with Creutzfeldt-Jakob disease have already been recorded after a blood transfusion from an infected donor.

In 2002, the United States first imposed restrictions on blood donation due to prion diseases.Medical institutions have been banned from accepting donated blood from people who spent three or more months in the UK between 1980 and 1996, or six months or more in some other European countries. This measure reduced the number of blood donors by 7%. Now the ban has been somewhat relaxed. Blood is not accepted from persons who have spent five or more years in European countries (except for the former USSR) since 1980, but a three-month stay in the UK has been preserved as an obstacle to donation. Similar regulations apply in Australia, New Zealand, Canada, France, Germany, Denmark, Switzerland, Poland and the Czech Republic.For some countries, this turned out to be a difficult measure. For example, in New Zealand, 10% of active donors became unusable in an instant.

It is difficult to check donated blood, as the number of prions in it is extremely small. Scientists have long been looking for a way to detect the presence of prions in the blood, and now two research groups have achieved their first success.

They have developed methods for detecting prions in blood that have shown high accuracy on a small number of samples from infected individuals and control groups.Both methods are based on culturing prions along with normal proteins and then activating them using sound waves. As a result, large clumps of abnormal proteins are formed, each of which stimulates the transformation of the structure in its neighbors. In this case, the reaction rate grows exponentially.

Neuroscientist Claudio Soto of the University of Texas McGovern School of Medicine and colleagues used the blood of 19 patients with the so-called classic Creutzfeldt-Jakob disease (sCJD) to test their method of analysis.These patients did not become infected with prions through cow meat or other external sources, their proteins themselves took on an abnormal structure. The exact causes of sCJD are unknown, in some cases the disease is caused by an inherited mutation, sometimes the mutation occurs spontaneously. Typically, sCJD affects people over the age of 50. In addition to blood samples from patients with sCJD, Soto and colleagues collected 137 control samples from healthy individuals. As a result, the test gave a positive result on all 19 samples containing prions, and never worked in the control group.

In another study, microbiologist Daisy Bougard from the University of Montpellier used a similar prion stimulation technique, but she and her colleagues previously extracted prions from samples by capturing them in magnetic nanoparticles. The technique made it possible to identify the blood of 18 patients with the classic form of Creutzfeldt-Jakob disease from 256 samples. She also found prions in two blood samples donated by sCJD patients before they showed their first symptoms.

Biochemist Jonathan Wadsworth, who studies prion diseases at University College London, calls the two studies long-awaited and promising. But Wadsworth also notes an ethical problem that will inevitably arise with the use of such tests. The doctor will have to inform the person that he has a serious, incurable disease, although we cannot yet determine for sure how specific these tests are and whether they give false positive results. Two million blood donors donate blood in the UK every year.And even a small number of false diagnoses can, according to Wadsworth, drastically reduce their number. At the same time, it is also impossible to refuse a blood test, as this would endanger thousands of lives.

Both research teams report that they intend to test their methods on more samples. The articles of the American and French teams are published on the website of the scientific journal Science Translational Medicine.

90,000 Infectious prion proteins detected for the first time in bacteria

Hello, Marina Astvatsaturyan is at the microphone! Until now, prions, infectious agents that cause degenerative brain diseases such as mad cow disease or Kreuzfeldt-Jakob disease, have been identified only in eukaryotes, that is, organisms whose cells contain a nucleus – these are plants, animals, yeast.The latest issue of Science published data indicating that a certain bacterial protein can behave like a prion that changes the conformation of other proteins. We are talking about a protein site in the bacterium of the causative agent of botulism Clostridium botulinum, which exhibits the properties of prions when transferred into the cells of yeast or E. coli bacteria. Prions are proteins whose primary structure allows them to fold in different ways. The prion version of a protein implies that its configuration, which, entering new cells, causes a change in the normal form of similar proteins to the prion, acting like an infectious agent.Prions were discovered in the 1980s as causative agents of fatal brain diseases – transmissible spongiform encephalopathies. Since then, pathologically folded proteins have been found in mammals, insects, plants and fungi, and not all prions have been found to be harmful to the host cell. The listed classes and kingdoms encompass eukaryotic organisms, which can be both unicellular and multicellular, but their cells are distinguished by a formed nucleus. In the study now being described, authors from Harvard Medical School in Boston, Massachusetts, using a special program tuned to recognize prion-forming proteins in yeast, analyzed about 60,000 bacterial genomes, focusing on a specific region of the bacterial protein.