BSE (Mad Cow Disease) and Variant Creutzfeldt-Jakob Disease (vCJD): Causes, Risks, and Prevention

Understand how BSE (mad cow disease) and vCJD affect humans and animals, the risks, symptoms, transmission, and prevention strategies.

By Medha deb

Created on Oct 3, 2025

Understand how BSE (mad cow disease) and vCJD affect humans and animals, the risks, symptoms, transmission, and prevention strategies.

BSE (Mad Cow Disease) and Variant Creutzfeldt-Jakob Disease (vCJD)

Bovine Spongiform Encephalopathy (BSE), widely known as mad cow disease, is a fatal neurodegenerative disease that mainly affects cattle. Its emergence and spread have raised major public health concerns due to its transmission risk to humans, where it causes the deadly variant Creutzfeldt-Jakob Disease (vCJD).

What Is BSE (Mad Cow Disease)?

BSE is a progressive and always fatal brain disease in cattle, first identified in the United Kingdom in the mid-1980s. The disorder causes the brain tissue to develop a spongy appearance, resulting in neurological symptoms and ultimately death. Unlike many infectious diseases, BSE is not caused by bacteria or viruses, but by an abnormal form of a naturally occurring protein known as a prion .

Prions are misfolded proteins that can induce other normal proteins in the brain to also misfold, causing a chain reaction of damage .
BSE is classified as a transmissible spongiform encephalopathy (TSE) due to the holes that develop in the brain, resembling a sponge.

The incubation period (the time from infection to appearance of symptoms) in cattle is long—usually four to six years. Once symptoms appear, death typically follows within weeks to months .

Symptoms of BSE in Cattle

Cows infected with BSE may exhibit a range of neurological and behavioral symptoms. Early in the disease, signs may be subtle, but they worsen as the disease progresses.

Abnormal behavior, including nervousness or aggression
Difficulty walking or standing (ataxia)
Irregular posture and incoordination
Weight loss, despite maintaining appetite
Decreased milk production

Typically, affected cattle will deteriorate rapidly after symptoms appear and will die within several weeks or months .

Causes and Transmission of BSE

BSE is not inherited and does not spread directly from cow to cow in the general environment. The main transmission route has been through contaminated feed:

During the height of the BSE epidemic, cattle were often fed meat-and-bone meal (MBM) made from the remains of other cattle or sheep, some of which carried the infectious prion .
This resulted in prion-contaminated feed passing from animal to animal.
Cows do not contract BSE by direct contact with infected animals or by living together in the same herd .

After the cause was identified, regulations were implemented to ban feeding ruminant-derived materials to cattle, which significantly reduced incidence .

BSE Outbreaks and Public Health Impact

BSE was first identified in 1986 in the UK and reached its peak in 1993, with about 1,000 new cases reported per week. Over 184,000 cases were recorded in the UK by the end of 2015, but strict safety measures led to a dramatic reduction .

Country	Cases Reported	Comments
United Kingdom	184,000+ (1986–2015)	Peak in 1993 (1,000/week). Major outbreak site.
United States	6 (as of 2018)	Extremely low prevalence.
Canada	20	Low prevalence.
Worldwide	Few cases reported annually	Nearly eradicated due to control measures.

BSE outbreaks were most severe in countries using contaminated feed practices. It is estimated that millions of potentially infected cows entered the food chain before control measures were enacted .

Variant Creutzfeldt-Jakob Disease (vCJD) in Humans

vCJD is a rare, fatal human disease caused by consuming products contaminated with the BSE prion. It is distinct from the classic Creutzfeldt-Jakob disease (CJD), which is not linked to the BSE outbreak and typically arises without known cause.

First identified in 1996 in the UK during the mad cow epidemic .
Strong scientific evidence supports that vCJD is caused by eating beef products contaminated with the nervous system tissue (brain, spinal cord) of BSE-infected cattle .
Human-to-human transmission is extremely rare but can theoretically occur through contaminated surgical instruments or tissue transplantation.

Symptoms of vCJD

Psychiatric symptoms such as depression, anxiety, or personality changes
Progressive neurological symptoms: unsteadiness, difficulty walking, involuntary movements
Memory loss and confusion
Eventually, patients become unable to move or speak, and death follows within about a year of symptom onset .

As of 2024, 233 confirmed vCJD cases have been reported worldwide .

How BSE and vCJD are Diagnosed

BSE and vCJD cannot be reliably diagnosed until symptoms appear, and there is currently no test for live cattle or people before the onset of advanced disease.

BSE in cattle: Diagnosis is made through examination of brain tissue after death .
vCJD in humans: Diagnosis is based on symptoms, MRI imaging, tonsil biopsy, and confirmation after death by examining brain tissue under the microscope .
Both BSE and vCJD result in characteristic spongy changes (vacuoles) in brain tissue.

Risk of Transmission to Humans

The main risk factor for vCJD is the ingestion of beef products containing nerve tissue from BSE-infected cattle .
There is no evidence that BSE can be transmitted by milk or milk products.
The infectious prion is not destroyed by standard cooking temperatures — even well-cooked beef can remain infectious if prion-containing tissues are present .

Regulatory and Preventative Measures

Following the identification of BSE, robust regulations and surveillance programs were implemented worldwide to protect both animal and human health.

Feed bans: The use of ruminant-derived protein (meat-and-bone meal) in cattle feed is strictly prohibited .
Age restrictions: In the UK and EU, cattle older than 30 months are excluded from the food and animal feed supply, or must be rigorously tested .
Specified Risk Material (SRM) removal: High-risk tissues (like brain and spinal cord) are removed from slaughtered cattle for human consumption .
Surveillance: Regular testing of at-risk or older cattle for BSE.
Traceability: Strict animal tracking and reporting systems to quickly identify and isolate any outbreaks.

Current Status of BSE and vCJD

Due to these stringent measures:

The incidence of new BSE cases in cattle has sharply declined; the disease is now considered almost eradicated in most countries.
New human cases of vCJD have also greatly diminished. Fewer than five new global vCJD cases are reported annually in recent years .

However, because prion diseases have very long incubation periods, ongoing surveillance and prevention efforts remain essential.

Frequently Asked Questions (FAQs)

Q: What causes BSE (mad cow disease)?

A: BSE is caused by prions, which are abnormal proteins that trigger disease without genetic material. These prions originated in cattle that consumed feed containing contaminated animal remains .

Q: Can humans get mad cow disease?

A: Humans do not get BSE, but can develop variant Creutzfeldt-Jakob Disease (vCJD) by consuming beef products contaminated with BSE prions .

Q: How do I know if beef is safe to eat?

A: Modern food regulations prohibit high-risk tissues from entering the food supply. The risk of vCJD from eating beef is now extremely low due to strict controls and monitoring in place since the late 1990s .

Q: Can cooking destroy the prion that causes BSE?

A: No. Prions are not destroyed by conventional cooking temperatures or procedures .

Q: What are the symptoms of vCJD in humans?

A: Symptoms start with behavioral and psychiatric changes (depression, anxiety), advance to impaired coordination and movement, mental deterioration, and eventually death .

Q: Is there a cure for BSE or vCJD?

A: There is currently no cure or effective treatment for either BSE in cattle or vCJD in humans . Prevention through regulation and surveillance is the best protection.

Key Takeaways

BSE (mad cow disease) is a fatal neurodegenerative disease in cattle caused by prions.
Humans can develop vCJD by consuming contaminated beef products.
Symptoms include neurological and psychiatric deterioration, inevitably leading to death.
Stringent animal feed bans, food safety regulations, and surveillance programs have nearly eradicated BSE and vCJD.
No cure exists for either disease; prevention is the primary defense.

Additional Resources

Centers for Disease Control and Prevention (CDC): BSE and vCJD information page
U.S. Department of Agriculture (USDA): BSE surveillance and regulations
World Health Organization (WHO): Food safety and animal health advisories

References

Author

medha deb

Medha Deb is an editor with a master's degree in Applied Linguistics from the University of Hyderabad. She believes that her qualification has helped her develop a deep understanding of language and its application in various contexts.

Read full bio of medha deb