Bovine encephalopathy

Martin Leach leach at mbcrr.harvard.edu
Thu Apr 14 10:20:50 EST 1994


In article <766323432snz at chatham.demon.co.uk>, ohgs at chatham.demon.co.uk
(Oliver Sparrow) wrote:

> BST is much in the news in the aftermath of the German ban on beef imports
> from the UK. I - and I suspect other readers - would welcome views on this
> disorder. 

It's nasty.

It has become an orthodoxy that BST is the consequence of an 
> infectious agent which is somehow passed through the food chain, notably 
> when ruminants eat food made from the bodies of animals which were themselves
> infected with BSE.
> 

If i believe correctly - scrapie is prevalent in old sheep (approx 40%).
Scapie which is in fact prion is the causitive agent. I have heard various
stories regarding how BSE suddenly exploded in england. It all starts off
with the chernobyl explosion. After the explosion radioactive dust etc..
drifted across europe and some landed over england, especially over the
sheep-farming areas. When tested these sheep contained unacceptable levels
of radioactivity to allow them for human consumption - as the british
public consume relatively large amounts of lamb meat. Instead of
slaughtering most of the sheep they were allowed to grow old and a very
large population of old sheep now inhabited UK. As 40% of old sheep usally
get scrapie anyhow, this now meant that there was a larger number of
scrapie infected sheep. Also around this time the extraction procedure for
making bonemeal (cow-feed supplement) was changed (according to Stan
Pruisner). The result being that scrapie infected material was rife in the
bonemeal feed, and given to cattle. The scrapie manifested as BSE in the
cows.




> I am aware of no systematic technique by which BSE can be deliberately 
> transmitted from an infected animal to another. Cows so innoculated show
> pathologies at the same rate as cows innoculated from controls. Strict
> controls on the re-cycling of animal protein into foodstuffs have been in 
> place for some years, yet the epidemic continues.

To test transmissibility of BSE infected material experiments performed
include:

intraocular injections of brain homogenate into eg. marmosets. This has
been performed by Ridley and Baker (i used to work in the same dept.
Psychiatry at th CRC in harrow for the MRC).

I have even seen a fax of a paper showing that BSE was transmitted to mice
by feeding them brain homogenate.

If i believe correctly, the afterbirth of animals born from BSE infected
animals contains high amounts of prion????(correct me) - this is eaten by
many animals.

> 
> From a position of some ignorance, may I make the following observations? 
> The disease is largely confined to dairy cattle and to their cross-bred
> offspring. The UK has spent thirty years systematically breeding its herds
> for high yields, using bulls which can sire tens of thousands of offspring,
> often incestuously. As virtually all race horses can trace their ancestry 
> to three stallions in the eighteenth century, so virtually all dairy cattle
> are the offspring of a few bulls, themselves drawn from a common background.
> 
> Might we, therefore, be seeing a disorder which has a genetic aetiology
> rather than something caused by a mysterious infectious agent (or
> environmental factor, such as organophosphorus dips and warble fly sprays, 
> as has been suggested)? 

I am not sure if a mutation in the prion gene has been found in cattle or
sheep.

The implications are considerable: a genetic BST
> could have no effect on those who eat meat from sick animals. One could 
> eliminate it within a generation. One can easily test for this: the 
> individual gentic records of all UK dairy cows are stored centrally and 
> it would be simple to test this view.
> 

Very nasty disease.
As is CJD and GSS.

See the channel 4 documentary - a couple of years ago. (You can see me
setting up PCR's etc... ;)


Martin Leach
-- 

.....          Martin Leach                Email:leach at mbcrr.harvard.edu 
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