What's the Beef? A Deeper Understanding of Mad Cow Disease

What is Mad Cow Disease and How is it Caused?

Mad cow disease, or bovine spongiform encephalopathy, is a disease that impacts the brain of a cow. It is a progressive neurological condition, which means that it impacts both the brain and spinal cord, and it becomes worse over time. Mad cow is not caused by a virus or bacteria, but by a misfolded protein known as a prion.  Signs and symptoms include:

• change in demeanor and behavior

• uncoordinated movements

• difficulty walking and standing

• weight loss

• spongy appearance of the brain from destruction of brain tissue

  
  

Prions 

Although innocuous sounding, all documented cases of prion disease have led to death within one year. Prions do not contain RNA or DNA; therefore, the cow’s body is unable to detect the infectious agent and employ an immune response. The misfolded protein initiates a chain reaction, causing other proteins in the brain to change their shape as well. The accumulation of prions clump with normal proteins, furthering the domino affect and causing irreversible, fatal damage to the brain.  The mechanism by which prion diseases are able to spread without any genetic material is not well understood, but it is hypothesized that once a single change in protein conformation occurs, new proteins of the same type are induced, thus contributing to the aforementioned chain reaction. Despite extensive research, there is not yet evidence to suggest the involvement of nucleic acids.  Additionally, prion diseases are found to remain infectious after being exposed to reagents that kill nucleic acids, further supporting this theory.  Magnetic resonance imaging (MRI) has allowed researchers to hypothesize that the mutations that cause prion disease destabilize protein structure by flipping its configuration into an unstable one, accumulating in the brain and causing programmed cell death.

Mad Cow Disease in Humans

Whilst mad cow disease mainly impacts cows, it can be spread to humans through consumption of contaminated meat; therefore, it is a notable risk factor amongst meat eaters living in regions where the disease is prevalent.  When observed in humans, mad cow is known as Creutzfeldt-Jakob disease.  Because it is neurodegenerative, symptoms largely target control of movement as well as development of problems with memory, such as dementia. The incubation period can span many years before prion accumulation reaches a high enough level to cause neurological symptoms.  Once symptoms begin, progression is rapid.  There is no cure or treatment, leading to death within a year.

Global Impact of Mad Cow

In the 1980s, a major outbreak of a deadly disease amongst cattle began in the United Kingdom and Ireland. Feeding animals with possibly infected product was then banned by the government, but the disease had already begun to spread into the supply chain for human consumption. In 1993, 1000 cases of infected cattle were reported per week. The first case off Creutzfeldt-Jakob disease, which was contracted from consumption of infected meat, was recorded in 1996.  Because there is no way to detect the presence of prions in the bloodstream, people living in high-risk areas were not eligible to donate blood until the ban was lifted in 2022. All prion diseases are fatal as there is no known cure or treatment, and any living thing infected with a prion disease will die of it. The only preventative measure is to avoid consumption of infected meat. More research needs to be done to determine with certainty the mechanism by which prion diseases occur and spread. 

Citations

“Donor Gives Blood after ‘Mad Cow’ Deferral Lifted.” American Red Cross, 27 Jan. 2023, https://www.redcross.org/local/ohio/northern-ohio/about-us/news-and-events/news/donor-gives-after-deferral-lifted.html.

“Mad Cow Disease in Humans: Diagnosis, Symptoms, Causes & Contagious.” eMedicineHealth, https://www.emedicinehealth.com/mad_cow_disease_and_variant_creutzfeldt-jakob/article_em.htm. Accessed 22 July 2025.

Medicine, Center for Veterinary. “All About BSE (Mad Cow Disease).” FDA, June 2024, https://www.fda.gov/animal-veterinary/animal-health-literacy/all-about-bse-mad-cow-disease.

“Prion Disease.” Cleveland Clinic, https://my.clevelandclinic.org/health/diseases/prion-disease. Accessed 22 July 2025.

Prion Diseases. 28 Feb. 2025, https://www.hopkinsmedicine.org/health/conditions-and-diseases/prion-diseases.

“The Deadly Effects of Mad Cow Disease in People.” Verywell Health, https://www.verywellhealth.com/mad-cow-disease-in-humans-2860865. Accessed 22 July 2025.

Vallabh, Sonia. “My Quest to Cure Prion Disease-Before It’s Too Late.” Youtube, 3 June 2024, https://www.youtube.com/watch?v=04PmEJaYKd0.

“What Is a Prion?” Scientific American, https://www.scientificamerican.com/article/what-is-a-prion-specifica/. Accessed 22 July 2025.

Assessed and Endorsed by the MedReport Medical Review Board