Wait, you can get CJD from eating brains? I knew about kuru and mad cow but never heard about CJD getting passed that way.
I just kinda figured eating brains wasn't much different than eating other organ meat, like chicken livers or gizzards or chitlins or whatever.
Confusingly, there are two neurodegenerative diseases which affect humans and are called CJD. Both are caused by prions. The first, which is usually just called
Creutzfeldt Jakob disease, is usually sporadic but can be inherited in families. Basically, you get unlucky and a typo in your DNA causes a protein to be made in the wrong shape. The bad protein builds up in your brain, you lose all of your cognitive and physical abilities over the course of a few months, and then you die.
The other type, called
variant Creutzfeldt Jakob disease, or vCJD, which is also caused by a prion. In this case, though, the prion isn't produced by your own body - it came from somewhere else. This is the type you can get from eating nervous system tissue (so, spinal cord, meninges, not just brain). Prions in general are poorly understood but it is believed that the prion that causes vCJD in people is
identical to the one that causes bovine spongiform encephalopathy (BSE), or "mad cow disease". Basically, you eat a sausage containing a misshapen protein, it takes up residence and builds up in your brain, you lose all of your cognitive and physical abilities over the course of a few months, and then you die. Survival time for the variant type is around one year and is slightly longer than that of classical CJD.
There was an
outbreak of vCJD in the UK in the 1980s and 1990s, which led to the discovery that it was caused by the same prion that gives cows BSE. Now, there are very stringent testing protocols and animal husbandry guidelines to
prevent cows with BSE from entering the food chain. This outbreak is the rationale behind some countries' forbidding some people who lived in Bongland from donating blood or blood products.
To add to the confusion, there were
cases of
classical CJD being transmitted via organ, cornea, and dura transplantation, blood and blood product transfusion, EEG electrodes, and improperly sterilized surgical instruments, although no new incidences of this means of transmission have been reported since the mid-70s. The physical characteristics of the misfolded protein which causes these diseases make them very, very hardy, and they can survive even autoclave sterilization.
Regardless of type or manner of transmission, the disease is rapidly progressive and always fatal. Here's a
chart comparing the respective clinical presentations of classical CJD and vCJD, for the curious.
From the example of
vCJD and BSE, we know that prion diseases can be transferred from animals to humans. Since we don't understand why this happens, it's safest to avoid eating nervous system tissue, including brain and spinal cord, from any animal. In addition to BSE, transmissible spongiform encephalopathies (TSE) caused by prions have been observed in
elk, deer, and caribou,
sheep and goats,
mink,
cats,
ungulates including American bison and various exotic antelope species, and
camels.
Prions are absolutely terrifying. Brains aren't that tasty, anyway.
Oh, and the human prion diseases have incredibly long incubation periods, with some patients not having symptoms until 10 or more years after infection. You could have it and not know. Cheers!
