Introduction | Are you familiar with the term mad cow disease? What about its human counterpart? These afflictions, collectively known as transmissible spongiform encephalopathies (TSEs), raise profound questions in the scientific community. Prions, the causative agents behind these maladies, represent a captivating area of inquiry within the field of biology due to their intrusive and lethal characteristics. Prions induce a state of neurodegeneration leading to aberrant behavior, hence the colloquial term “madness.” Yet, despite their microscopic size, prions elicit perplexity and trepidation among researchers, challenging conventional understanding of pathogenic agents and prompting intensified investigation into their mechanisms of action.
Mad Cow Disease | Bovine spongiform encephalopathy, commonly known as mad cow disease, traces its origins to the consumption of contaminated cattle feed. This progressive and invariably fatal affliction is of particular concern due to its interrelatedness with other prion diseases such as scrapie in sheep and goats, chronic wasting disease in cervids including deer, elk, and moose, and notably, Creutzfeldt-Jakob Disease, often referred to as human mad cow disease. Clinical manifestations of these prion disorders in non-human species encompass a spectrum of symptoms, ranging from behavioral aberrations to loss of coordination, weight loss, and diminished milk production. Notably, the unpredictable nature of prion propagation contributes to the variability observed in symptomatology across affected individuals.
Prions | What exactly constitutes a prion? According to researchers, it’s essentially a protein gone rogue, misfolded and wreaking havoc within the body. It is also of great interest due to its organic origin while lacking DNA. Something fascinated about prions is that scientists still do not know how to kill them! They are resistant to conventional autoclaving, and can survive severe temperatures, which defies many biological organism and tissue behavior. Despite extensive scientific inquiry, the enigmatic nature of these minuscule assailants remains largely shrouded in mystery, adding an extra layer of dread to prion-associated diseases. While efforts have yielded medications that slow the spread within the body, a definitive cure does not exist yet. Diagnosis of these maladies in humans typically involves an array of tests ranging from MRIs and spinal taps to EEGs and blood analyses, alongside comprehensive neurological and physical evaluations. However, unequivocal confirmation of prion presence necessitates the invasive measure of brain tissue biopsy, a procedure typically conducted after death — a sobering reminder of the complexities of prion pathology.
Human Variants | When it comes to prion diseases in humans, Creutzfeldt-Jakob Disease (CJD) takes center stage, though the modern-day risk no longer stems from tainted cattle meat. Surprisingly, transmission can occur through medical procedures if equipment isn’t adequately sterilized. While CJD can have hereditary roots, it can also manifest sporadically or, in the case of variant CJD, be acquired from contaminated meat. Symptoms such as rapid cognitive decline and neuromuscular dysfunction characterize its progression. As for the risk associated with consuming meat, that’s a judgment call each individual must make. Statistically speaking, the likelihood of encountering an infected serving in today’s world is minuscule, estimated at a mere 1 to 10 billion chance. Additionally, the demographic skew towards individuals aged 50 to 75 adds another layer of complexity. Mitigating risk involves stringent sterilization of medical equipment, refraining from organ or tissue donation if infected, and opting for solid beef over ground, purportedly a safer choice regarding prion contamination. Despite these precautions, widespread panic is unwarranted. Since 1996, only four cases of variant CJD have been reported in the United States. Moreover, it’s worth noting that CJD isn’t transmissible between individuals and isn’t linked to cow milk consumption, as the infective prion tissue isn’t bloodborne or airborne.
Other Prion Diseases | You may have also come across the tale of fatal insomnia, a hereditary affliction notorious for inducing death through prolonged sleeplessness. This condition falls under the umbrella of prion diseases, as it shares the underlying mechanism of misfolded proteins in the brain driving its progression. Another haunting example is Kuru, colloquially known as the “laughing sickness,” which gained infamy within New Guinean culture. Historically, Kuru spread through the ritualistic consumption of deceased tribe members’ brains, undertaken as a means of honoring and preserving their memory. Tragically, this practice inadvertently facilitated the transmission of brain prions, disrupting the central nervous system of those partaking in the ritual. #
References #
Prion Diseases. Johns Hopkins Medicine [Internet]. Accessed 2024. https://www.hopkinsmedicine.org/health/conditions-and-diseases/prion-diseases#:~:text=Prion%20diseases%20occur%20when%20normal,changes%2C%20and%20difficulties%20with%20movement. Mad Cow Disease (Bovine Spongiform Encephalopathy). Johns Hopkins Medicine [Internet]. Accessed 2024. https://www.hopkinsmedicine.org/health/conditions-and-diseases/bse-mad-cow-disease-and-vcjd#:~:text=Mad%20cow%20disease%2C%20or%20bovine,diseases%20caused%20by%20a%20prion. Bovine Spongiform Encephalopathy (BSE). Animal and Plant Health Inspection Service, U.S. Department of Agriculture [Internet]. Accessed 2024. https://www.aphis.usda.gov/aphis/ourfocus/animalhealth/animal-disease-information/cattle-disease-information/cattle-bse/cattle-bse#:~:text=Affected%20animals%20may%20display%20changes,or%20vaccine%20to%20prevent%20BSE.
- The story of Kuru from New Guinean tribes comes from a book titled “The Tale of the Dueling Neurosurgeons” by Sam Kean. I will write about this book more in the future because I highly recommend it!