Mad Cow Diseases and Milk

hlr at aber.ac.uk hlr at aber.ac.uk
Thu Mar 28 09:05:05 EST 1996

In article <961928121920 at ibm3090.bham.ac.uk> GREENA at UK.AC.BHAM.IBM3090 writes:

>Any recommendations of readable review articles on BSE/JCD?  Would
>have to be understandable by physiology/biochem graduate I'm afraid.

Lacey's book "Mad Cow Disease" (1994) Cypsella Press is good. When quoting 
this before I have had comments saying that his outlook is biased, but most of 
what we hear has a pro-government bias so if you read from a variety of 
sources things should even out. There are a few web sites with useful stuff, 
they've recently been mentioned on the group - mail me if you need the URL's

>>>Can it also be passed via milk?
>>The answer is as yet unknown. Experiments have been done where milk has been
>>injected into mice to see if they develop symptoms but as far as I know none
>>have. HOWEVER, these experiments involved injecting only 1 or 2 microlitres
>>into a mouse (only one injection per mouse) and the prion may be there at
>>lower concentrations than would be detected by this method.

>What does the dose/response curve look like? Does the above imply a "safe

No idea whether this has been done.

>So if bovine blood is infectious, how is it that muscle tissue isn't?

If an animal can be infected by eating prion protein (true) and the prion gets 
to the brain (true) then it presumably goes via the blood (not proven but a 
few of us have raised this point on this group and noone has suggested any 
alternative route). I don't think anyone has managed to infect mice or 
whatever with cow or sheep blood but mink and human blood are infectious - see 
Lacey's book.

The government have made the claim that muscle is safe. By the reported 
drop in beef sales they obviously haven't convinced many people  - myself 
included. I'm happy to believe that the highest levels of infective tissue are 
in the brain, spinal cord and retina, but that doesn't convince me that 
consuming every other part is safe.

If BSE originated from sheep scrapie and if it occurs in the same range of 
tissues (2 big if's) then it is worth noting that sheep scrapie infectivity 
has been found in brain, spinal cord, peripheral nerve, lymph node, spleen, 
gut, liver, thymus and bone marrow.

It is relatively easy to avoid beef in the diet (if you remember that pork 
sausages can contain a certain %age of beef!!), avoiding milk is more 
difficult and avoiding gelatine is almost impossible (it is used in cosmetics 
and medicines as well as foods). 

Now my question(s):
Gelatine is made from bones but is it just bones that end up in the pot or 
other stuff too? I suppose the bone marrow goes in anyway? If infected 
material ended up in the pot would the prion protein be purified along with 
the gelatine? How pure is food-grade gelatine anyway?

|          Dr Hazel Marie Davey   hlr at aber.ac.uk         |
|Sefydliad y Gwyddorau Biolegol*Inst. Biological Sciences|
|Prifysgol Cymru               *      University of Wales|
|        ABERYSTWYTH, Dyfed, CYMRU / WALES SY23 3DA      |
|            http://pcfcfh.dbs.aber.ac.uk/index.htm      |

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