You dont hear much about mad cow today, but the threat still looms.
Heres what happened to this nightmare germ.
In 1986, farmers in the UKbeganto report strange behavior among some of their cows.
Illustration: Vicky Leta
The affected bovines had trouble walking and getting up.
They also started acting increasingly nervous and sometimes violent (hence the mad moniker).
Within a few weeks to months of these symptoms emerging, the cows would die.
Soon enough, the ailment had a formal name: bovine spongiform encephalopathy, or BSE.
But prion proteins can shapeshift into a misfolded version, one that converts normal prions into more of themselves.
Over time, the exponential accumulation of these rogue proteins destroys the brain.
Usually, these diseases emerge spontaneously or through inherited mutations that make our prions prone to misfolding.
People then got infected by eating meat infused with contaminated brain and spinal cord tissue from BSE cows.
These transmission chains were aided by the fact that prions are naturally resistant to most routine forms of decontamination.
By the mid-1990s, the UK formally banned the practice, as did most every other country eventually.
And even within the UK, annual BSE cases soon dropped off a cliff.
Still, millions of BSE-infected cattle might have entered the food supply before the epidemic was recognized and contained.
But we got lucky.
Thats not to say that the BSE and vCJD outbreaks were nothingburgers.
And the knowledge weve gained from studying them has helped scientists better understand neurodegenerative conditions like Alzheimers and Parkinsons.
And while mad cow was defeated, its not gone.
Countries even today still have toreport and aggressively containthe occasional case of this form.
And other rare routes of prion transmission exist as well, such asneedle stick accidentsin the lab.
Prions remain an important public health threat in other animals, too.
To date, theres nosolid evidencethat chronic wasting disease can infect and sicken humansfor now at least.
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