[incrudible]

I remember that in the 90s, when "mad cow disease" was dominating the headlines, it was predicted that there would be an exponential increase in cases, decades down the line. The same point about prions being virtually indestructible was being made, the same concerns about surgical equipment and blood donations were raised.

Suffice it to say, the prion disaster did not materialize, so I'm skeptical about the same story being repeated almost verbatim today. My guess is that prions aren't all that contagious after all, especially after basic food preparation measures.

[ipython]

The concerns about blood donations continue to this day. A few years ago I went to a blood bank event not even thinking about vCJD and was turned away because I happened to live in Europe for more than 6 months in the early 90s.

It is a bit unnerving to know you may or may not have a disease that there is no test for, and symptoms may not appear until decades later.

[813594]

You might want to check again to see if you’re eligible now. They ended some of these restrictions on blood donation in the summer of 2020.

[ipython]

Thanks! It appears that the new restrictions no longer apply to me. I’ll be off to give blood later this month.

[incrudible]

...out of "an abundance of caution".

> It is a bit unnerving to know you may or may not have a disease that there is no test for, and symptoms may not appear until decades later.

That's true for many neurodegenerative diseases. If that's unnerving to you, better stay away from WebMD...

[hajile]

Who knows. I'll give you an interesting thought.

There is NO single, conclusive test for Alzheimer's disease. The symptoms are almost identical to CJD (human mad cow) with the biggest differentiator being time from diagnosis to death. Even Amyloid-beta plaque buildup is often (though not always) noted in CJD patients [0][2]. Likewise the other Alzheimer's marker tau protein is also elevated in CJD patients [3]. I'd note that we don't actually know that CJD must progress over 1-2 years rather than a decade -- it is an observational assumption.

Between 15-30% of Alzheimer's diagnosed patients also don't have the normal Alzheimer's brain symptom (presumably amyloid buildup) either. Alzheimer's as cause of death was 17.6% in 2000, but is now 37.3% in 2020.[1] Because CJD is defined as killing quickly, it isn't even checked for in such cases (a kind of self-fulfilling prophecy if the diagnosis criteria aren't actually accurate). It doesn't help that cleanup of a contaminated area is time consuming and costly (not to mention potential negative press and panic).

This isn't a new idea, but perhaps those fears were somewhat true, but have been buried under our lack of knowledge of protein diseases.

[0] https://pubmed.ncbi.nlm.nih.gov/3092727/

[1] https://alz-journals.onlinelibrary.wiley.com/doi/full/10.100...

[2] https://pubmed.ncbi.nlm.nih.gov/12891683/

[3] https://pubmed.ncbi.nlm.nih.gov/20881758/

[incrudible]

> The symptoms are almost identical to CJD (human mad cow) with the biggest differentiator being time from diagnosis to death.

Ordinary CJD has a much lower median age of death (68 years) than Alzheimer's (88 years), but vCJD (the form that is believed to be caused by contaminated food) has a median age of death of only 28 years.

https://en.wikipedia.org/wiki/Creutzfeldt%E2%80%93Jakob_dise...

A surge in young or middle-aged dementia cases would likely not have fallen under the radar.

> Between 15-30% of Alzheimer's diagnosed patients also don't have the normal Alzheimer's brain symptom (presumably amyloid buildup) either. Alzheimer's as cause of death was 17.6% in 2000, but is now 37.3% in 2020.[1]

You have mistaken the rate of deaths (per 100,000) for the percentage. When judging this increase, one must consider that in the same timeframe, the mean age of the population has risen by 10% and life expectancy increased by more than two years.

[hajile]

> You have mistaken the rate of deaths (per 100,000) for the percentage. When judging this increase, one must consider that in the same timeframe, the mean age of the population has risen by 10% and life expectancy increased by more than two years.

Sorry, knew what I meant, but messed up what I typed. In any case, doubling the death rate per 100k is still much greater than the 10% age and 2-3% lifespan increase would indicate. Alzheimer's mortality had increased 16x between 79 and 91 (from a mere 857 to 13,768 in 1991[0]. The previous study I quoted above put the 2018 mortality at 122,019. Alzheimer's is now the 6th leading cause of death and continues to rise at a rapid rate.

> Ordinary CJD has a much lower median age of death (68 years) than Alzheimer's (88 years), but vCJD (the form that is believed to be caused by contaminated food) has a median age of death of only 28 years.

This is the crux of the problem.

We have experimental knowledge about this from kuru. The last patient displayed symptomatic kuru some 5 decades after the cannibalistic practices had stopped.

Do only young people eat meat? If all age groups eat meat at equivalent rates and infection rates in cattle are constant (believed to be around 1 in a million IIRC), then the median age should be the population median age PLUS a shift for however long it takes to become symptomatic.

Linkage is also important. How do we know that CJD and vCJD are different? We made that distinction arbitrarily and don't have evidence that "normal" CJD is not caused by external sources. Official vCJD cases are around 200 over the past 30 years, so there isn't exactly huge amounts of data to pull from either.

If CJD really did explode in the 80s-90s, then you would expect the older generation to become symptomatic at an older age than would be typical if the disease were common in the decades before.

There seems to be a connection with being vegetarian/vegan and alzheimer's but how much is due to not eating meat and how much is due to overall healthy lifestyle is hard to determine.

Something weird is going on with Alzheimer's disease and the legit explosion in cases over the last 30 years (both per capita and as cause of death in the elderly) give reason to wonder what weirdness is going on.

[0] https://www.cdc.gov/nchs/data/series/sr_20/sr20_028.pdf

[chasil]

Here is another major difference:

"We know that the β-A4 amyloid of Alzheimer’s disease also derives from a normal host protein that in diseased people accumulates in the brain, but it does not have the ability to transmit disease to a healthy person. Why this difference?"

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1114482/

[xenadu02]

We have no idea if US Beef is infected. The USDA prohibits anyone from testing their cows and ended their spot-testing program (which was a joke).

So unlike Europe we never reckoned with the problem and don't know if it is currently spreading. For human exposure we would not yet be far enough along to know if the US Beef supply either is or was contaminated.

Personally I have basically stopped eating beef for this reason.

[incrudible]

It is estimated that hundreds of thousands of infected cattle entered the food chain in the 1980s. The total number of cases of vCJD is at less than 250 as of 2018.

Feeding practices that led to BSE have changed, the USDA is still testing for BSE, and if the disease was spreading, we'd probably notice it at some point.

Personally, I'd be far more worried about cattle farming practices spawning some sort of super-resistant flesh-eating bacteria than anything related to BSE.

[mannerheim]

Also worth noting that only four of those cases occurred in the US, and none of those have been traced to US beef; in each of these cases, the patients had spent a significant time living outside of the US (and two of the patients lived in the UK, whose cows were known for having BSE).

https://www.cdc.gov/prions/vcjd/vcjd-reported.html

[whatshisface]

>The USDA prohibits anyone from testing their cows

Huh? Why would they prohibit testing?

[mannerheim]

The USDA does test a sample of cows, but prohibits companies from doing testing on their own cows probably because the tests would likely be inaccurate and provide an unwarranted impression of safety:

> NOT A FOOD SAFETY TEST

> BSE tests are not conducted on cuts of meat, but involve taking samples from the brain of a dead animal to see if the infectious agent is present. We know that the earliest point at which current tests can accurately detect BSE is 2-to-3 months before the animal begins to show symptoms. The time between initial infection and the appearance of symptoms is about 5 years. Since most cattle that go to slaughter in the United States are both young and clinically normal, testing all slaughter cattle for BSE might offer misleading assurances of safety to the public.

> ...

> Why doesn't USDA test every animal at slaughter?

> There is currently no test to detect the disease in a live animal. BSE is confirmed by taking samples from the brain of an animal and testing to see if the infectious agent - the abnormal form of the prion protein - is present. The earliest point at which current tests can accurately detect BSE is 2 to 3 months before the animal begins to show symptoms, and the time between initial infection and the appearance of symptoms is about 5 years. Therefore, there is a long period of time during which current tests would not be able to detect the disease in an infected animal.

> Since most cattle are slaughtered in the United States at a young age, they are in that period where tests would not be able to detect the disease if present. Testing all slaughter cattle for BSE could produce an exceedingly high rate of false negative test results and offer misleading assurances of the presence or absence of disease.

> Simply put, the most effective way to detect BSE is not to test all animals, which could lead to false security, but to test those animals most likely to have the disease, which is the basis of USDA's current program.

The ban might not be warranted (I don't believe it is myself), but it is important to be aware that testing for BSE may not be accurate at the time most cows are slaughtered.

https://www.usda.gov/topics/animals/bse-surveillance-informa...

[pm90]

Because businesses don’t want to bear the loss (financial and likely reputational) of finding out that their beef contains prions.

[whatshisface]

Thereby combining all of the potential isolated, individually bad disasters into one enormous fully-correlated watershed moment when all companies are simultaneously found to be selling prion-containing beef...

[ggreer]

If US beef was contaminated, wouldn’t there be thousands of cases of vCJD[1] by now?

1. https://en.wikipedia.org/wiki/Variant_Creutzfeldt–Jakob_dise...

[imglorp]

Yes there could be. It remains latent for years after consuming the infected meat. Guess we'll find out! ¯\_(ツ)_/¯

[ggreer]

We did find out. The US has had a total of 4 cases of vCJD, all of which were contracted overseas.[1] For comparison, the UK has had over 170 cases.[2]

1. https://www.cdc.gov/prions/vcjd/vcjd-reported.html

2. See table 3 in the PDF on this page: https://www.termedia.pl/Review-article-r-n-r-nVariant-Creutz...

[mannerheim]

It isn't really possible to prepare beef in a way to eliminate prions; you have to just make sure the beef you're preparing doesn't have them.

[incrudible]

I'm aware that prions are hard to destroy, but that's a different question as to whether they are contagious. A lot of contaminated beef did enter the food chain, yet the expected surge in vCJD did not occur. I would expect cooking to have some impact here, but that's just a guess.