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Prions

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Re: Prions

#121

Post by dnautics »

hajile wrote: post #120
dnautics wrote: post #59

Earlier quoted context omitted.

Cwd is essentially the same as bse and cjd and scrapie. It's actually the one that you have to worry about the least. For unknown reasons, there is not species crossover between deer and cow/sheep/humans (I was briefly investigating the molecular mechanisms for this but finished my phd before getting results). As for why the grazing animals can spread prion, my guess is that the prion protein is highly concentrated i…

The CDC disagrees with your assessment. Do you have any sources about this? According to the CDC, CWD is spread NOT just through saliva, but also feces, blood, urine, etc. In addition, it CAN spread to Squirrel monkeys. The long-term affects on macaques is still being established (on of the reasons kuru took so long to discover was that it took decades for the monkey to develop symptoms). If exposure is dangerous to…

So I should have disclaimed that my information is as of 2009, which is the last time I touched this stuff, but that site said there was not successful transmission into monkeys in another experiment by the lab. I mean these experiments are extreme, high dose boluses of material straight into the brain. If at least one experiment failed to do that into monkeys that says something, even if they managed to get it in a later one, unless there was some revelation that they had done it wrong the first time.

Re: Prions

#122

Post by mannerheim »

whatshisface wrote: post #67
xenadu02 wrote: post #44

Earlier quoted context omitted.

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 re…

> The USDA prohibits anyone from testing their cows Huh? Why would they prohibit testing?

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...

Re: Prions

#123

Post by Metacelsus »

The article is completely wrong about the prion mechanism.

>The prion’s structure is corruptive because it is not a copy but a mirror image of the protein, flipped in the opposite direction. In technical terms, some groups of prions have the opposite chirality—Greek for “handedness”—of their normal cousin proteins. The prion is doubly corruptive because it does not keep its inversion to itself: when it encounters its mirror image—a normal protein—it convinces that image to flip, to change chiralities and join the prion group.

The amino acids don't change their chirality, only the protein's secondary structure.

Re: Prions

#125

Post by danaris »

derekp7 wrote: post #47
beiller wrote: post #19

Earlier quoted context omitted.

If it was more deadly it would spread less quickly. That's how diseases work from my vague university memories of an epidemiology course. They are on a spectrum of deadly to contagious.

What actually causes this though? For example, take something like HIV that takes a long time to show symptoms, but have an airborne version of it. Do the things that make viruses airborne also keep them from having a long gestation period and also highly lethal?

(Not an immunologist/virologist/biologist of any stripe. The following is my rough layman's understanding of the answer to this question. Would love to be corrected by someone with more formal knowledge of the subject.)

My understanding is that the main reason is a biological application of the principle of parsimony: Evolutionarily, organisms don't generally evolve lots of different things all at once. Thus, if you have a novel variant of a virus, it is highly likely to be mostly like existing variants, but with a very small number of changes.

Basically, you can think of it as the virus having to hit a particular threshold of a mutation direction that increases transmissibility to become widely-spread, but also has to hit a particular threshold of a mutation direction that increases lethality in order to become very dangerous.

As soon as it hits that transmissibility threshold, that is the version of the virus that's going to spread, and hitting both those thresholds at the same time is going to be incredibly rare.

What's much more likely (and genuinely concerning) is the possibility that a virus that has already become highly transmissible evolves more in the "lethality" direction and goes from being a widespread nuisance to being a deadly pandemic. The longer we let something like COVID remain widespread, as I understand it, the more likely we are to see a variant emerge that retains its high transmissibility but also gains a higher lethality. However, as we can see from the fact that the bodies are not piling up in the streets, even after nearly a year and a half of a pandemic form of a particular virus, it's by no means guaranteed that something like that will happen, even at a small scale.

Re: Prions

#126

Post by ficklepickle »

bb123 wrote: post #101
Scandiravian wrote: post #55

Earlier quoted context omitted.

I think there's better arguments than a risk of prion disease for cutting beef (or meat in general) from your diet - not sure if your comment is meant as a joke that I'm not catching, so I'll hold out on going into details unless you're interested :-)

Not meant as joke. I'm aware that there are lots of good reasons for not eating beef, I was wondering if prion exposure risk is one of them, as the meat/no-meat argument is one I try to revaluate regularly as new info comes to light. I eat beef once or twice a week as I have found it hard to get sufficient iron, protein, b12 and enough calories in general without it (and other meats). That and it tastes good, but I'm…

I take a liquid supplement called Floradix for b12/iron. It is made from yeast and vegetables. I'm prone to anemia and it has been immensely helpful.

Re: Prions

#127

Post by mannerheim »

incrudible wrote: post #87
xenadu02 wrote: post #44

Earlier quoted context omitted.

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 re…

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-resi…

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

Re: Prions

#128

Post by kijin »

Mordisquitos wrote: post #20
adrianN wrote: post #17

Earlier quoted context omitted.

Luckily humans can survive quite well without any meat at all.

So can deer.

Unlike deer, at least some humans are capable of not pooping and drooling on other people's food.

Re: Prions

#129

Post by sparker72678 »

If the issue is a protein folding the wrong way, and inducing that fold into nearby proteins, why doesn't this just happen spontaneously in humans?

Re: Prions

#130

Post by oxymoran »

Scandiravian wrote: post #40
canadianfella wrote: post #5

I’m surprised these haven’t been weaponized by terrorists.

I think the timescale is too long for it to be an effective tool for terrorists Terrorism is first and foremost a propaganda strategy to destabilise the political system in the target country and recruit new members to the organisations cause Since prions take decades to progress, a terrorist attack using such a weapon, would probably not create the shock and outrage, that makes headlines

It would be the perfect timetable for an adversarial country looking to become the next superpower to use as a bio weapon though.
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