Prions: testable? traceable?

[epepke]

Originally posted by garys_2k Anyway, I've been eating turkey-based cold cuts for years (and I'm sure they use equally appetizing extraction techniques for that), and I'm not aware of any bird-based prion diseases so far.

Trouble is that there have been a number of cases of serious contamination in turkey-processing plants recently.

Personally, I don't worry about it. The change of getting a prion-based disease, even if you're British, is so many orders of magnitude lower than the chance of choking to death that it might as well be zero.

 

[Prester John]

Anyway you're all worrying about the wrong thing. Its your blood supply you need to worry about. There a a chance that prions ( which are the current best theory for TSE's) are transmissable in blood donations. Add in the difficulty in detecting them. Mix in a little many blood donors have recieved blood donations. What have you got, a real big problem!
1) If you can test, do you test all donors, what if they don't want to know they may have a progresivly fatal disease. Even if we detect the prion portein we do not know that disease will follow. Insufficient information. Very large ethical issues
2) So you exclude all donors who have recieved blood donations. Wow, bang goes the blood supply, or at least a large portion of it. If you offer the screening test, people may avoid donating because they do not want to know. Again big loss to blood supply.
3)Who cares ? Well there is a lot of work being done to reduce the hospitals need for blood, but it is still a large requirement that saves many lives.

One of the biggest problems is that we simply do not know enough abouts TSE's.

 

[RichardR]

Anyway you're all worrying about the wrong thing. Its your blood supply you need to worry about. There a a chance that prions ( which are the current best theory for TSE's) are transmissable in blood donations. Add in the difficulty in detecting them. Mix in a little many blood donors have recieved blood donations. What have you got, a real big problem!
1) If you can test, do you test all donors, what if they don't want to know they may have a progresivly fatal disease. Even if we detect the prion portein we do not know that disease will follow. Insufficient information. Very large ethical issues
2) So you exclude all donors who have recieved blood donations. Wow, bang goes the blood supply, or at least a large portion of it. If you offer the screening test, people may avoid donating because they do not want to know. Again big loss to blood supply.
3)Who cares ? Well there is a lot of work being done to reduce the hospitals need for blood, but it is still a large requirement that saves many lives.

One of the biggest problems is that we simply do not know enough abouts TSE's.

Actually, I was just about to ask about this.

Is there any hard evidence the CJD can be spread by blood transfusion? I always thought you got it only by eating the brains and spinal cord. See this "Scientist" article http://www.the-scientist.com/yr2001/oct/opin_011001.html

(The) plan to restrict the (blood) donor population is based not on hard, scientific evidence but on two unsupported fears: that thousands of Europeans are in a preclinical, undiagnosed state in the development of nvCJD and that nvCJD is transmitted by blood.

...

Restricting the donor base in this manner would reduce the available supply of blood by 10 percent over the whole country with major coastal metropolitan areas being hardest hit. Therefore, the blood banks of New York and other cities will not be replenished by blood supplied by other parts of the United States. According to the New York Blood Center, if blood from European sources is deemed unacceptable for American recipients and no other source of blood is found, 200 of the thousands of life-saving transfusions per day will not occur in the greater New York area. By trying to protect Americans from blood-borne illness, the FDA will withhold lifesaving treatment from those who could otherwise be saved by blood that is almost assuredly safe.

...

Regardless of the hardships placed on US blood banks, if it were proven that nvCJD could be transmitted via blood, then removing any donor potentially infected would be reasonable. However, no hard evidence exists that nvCJD can be transmitted by blood. There is abundant evidence supporting the conclusion that classical CJD, a closely related disease to nvCJD that is transmitted by contaminated surgical instruments or tissue grafts, is not transmitted by blood transfusions. Also, no hemophiliacs in the United Kingdom or elsewhere have contracted nvCJD, suggesting that there is little increased risk from accepting blood donations in the development of nvCJD. The blood factors that hemophiliacs receive are heat treated to reduce the risk of iatrogenic spread of infectious disease. However, prions are extremely stable under conditions that destroy most proteins such as heat treatment; therefore, the fact that no hemophiliacs have developed nvCJD is significant. Furthermore, a few patients are known to have accepted blood from individuals who later developed nvCJD and all of these patients remain healthy.

I offer this article without comment. I have no idea if he is right – is it junk science or is "CJD can spread by blood" junk science?

 

[Prester John]

There is a study currently ongoing in sheep, whereby sheep have been infected with TSE (via the oral route i believe) and then blood from these infected sheep is transfused to healthy sheep. At least 1 of the transfused sheep has developed the TSE. As i said the study is ongoing and the protocol may be open to crtitism, i cannot recall all the details. New scientist carried an article on it i think. There is also a possible human transmission case:

vCJD death linked to blood transfusion

http://www.newscientist.com/news/news.jsp?id=ns99994498

which i found from this page

http://www.newscientist.com/news/search/dosearch.jsp?advsearch=CJD&searchtype=all&x=25&y=7

which contains a number of interesting articles

 

[Rolfe]

One person in Britain recently died from CJD, and it turned out that he had previously had a blood transfusion from someone who, while healthy at the time of donation, himself had subsequently died of CJD.

It's still possible this could be pure coincidence, but they're talking about banning everyone who has ever had a blood transfusion themselves from donating blood. Not sure of the point - might be more rational to ban everyone who ate beef after whenever it was in the 1980s from giving blood, but oops, we wouldn't have any blood then, would we?

They also said they'd be contacting everyone else who'd had blood from that donor. My first thought was, that's daft - you can't do anything for them, so why give them a nervous breakdown over what in any case is still a hypothetical risk? Then I thought, if they're boxing really clever, the way to handle this might be to make that announcement, then tell nobody. Who knows?

The total death toll from vCJD is still low - well under 200. In a population of over 60 million, most of whom probably eat beef. Deaths from food poisoning are undoubtedly way higher. By the way - 80% of poultry meat is contaminated with Campylobacter jejuni, and doesn't a lot of seafood have too much mercury, and maybe maybe it would be better if we just all starved to death...?

Rolfe.

 

[SteveGrenard]

CWD in wild Cervids Reported

from:

Canadian Press , 17 Dec 2003


<http://www.cp.org/english/hp.htm>


4 new cases of chronic wasting disease in the province has Saskatchewan
Environment pondering what to do next.

Yesterday, the provincial environment department confirmed that 4 mule deer
shot near Swift Current during the first half of November tested positive for
the disease. That brings the total to 11 cases [since fall 2003] and 23
since testing began.

There is no evidence of exactly where the disease originated in the
province or whether it can spread from cervids to other species.

Val Geist, of the University of Calgary, says chronic wasting disease (CWD)
is closely related to mad cow disease and should be taken more seriously.
Geist suggests [that is] because urbanites aren't particularly concerned with what's going on in the wild.


note from T Garland, DVM to me in an e-mail:

CWD existed in parts of Colorado
and Wyoming for 40-50 years, and there is no evidence of its
transmissibility to other species.

SG note:

So CWD is not just found in farm raised cervids but in asome areas in wild cervids as well. Somebody here mentioned that the feed to blame for BSE is sometimes diverted to feed wild deer and elk, more of which are being farm raised today than ever before.
Fifty years ago farm raised and fed deer and elk were probably a rarity.

 

[Prester John]

They also said they'd be contacting everyone else who'd had blood from that donor.

We have to do that. A duty of care is owed to people who may have contracted a TSE from a blood transfusion. Whether or not they want to know is a different matter. Some people will, others will not, its part of the difficulty of this whole subject.

As for baning people who have recieved transfusions. If TSE's are transmissable by transfusion, then those who have recieved blood transfusions are in a higher risk category than those who have not recieved transfusions. Blood safety is taken to a very high level, eg Risk of Hepatitis B from Blood transfusion is 1/500,000, but work is still being done to reduce it futher. There is a high public expectatation for the safety of the blood supply, and there is a potential very costly legal case every time something slips thro' (UK yes!).

As for wild TSE's in the america's, as far i i know they have always been there, probably always will, just not been acknowledged until recently. All those hunters who been shooting and eating stuff better watch out