BSE and CJD

Tom Thatcher ttha at uhura.cc.rochester.edu
Thu Mar 21 08:46:11 EST 1996


In <4iptm2$1d0 at clus2.ulcc.ac.uk> dcurtis at hgmp.mrc.ac.uk (Dave Curtis) writes:

>So, who's got an opinion on the relationship between CJD and BSE? 

>Till today, the mainstream British scientific opinion has been that
>there could possibly be a relationship but on balance one couldn't say
>one way or the other. The British Medical Journal recently published a
>number of opinions and it was clear there was no consensus, nor a
>basis for one. However suddenly today we hear that ten cases of CJD
>were "probably" related to BSE.  If there can be an aetiological
>relationship then that's pretty important - one scientist was
>presenting the view that these would be cases from right the start of
>the BSE epidemic, when very few cows were infected. He said there
>could be as many as a million cases, which I suppose is theoretically
>possible but sounds pretty unlikely to me. Are we seeing the start of
>a major epidemic (pandemic?)? The AIDS of the next millenium?

Well, the article I read (in the US) said that some committe had looked 
at 10 cases of CJD that were unusual in the age of onset, and decided that
BSE could not be rules out (I don't think the article used the word 
"probably").  The interesting thing about this disease the the way the
host range works.  For example, brain matter from a scrapie infected sheep
can infect cows and mice but not guinea pigs, but if you pass sheep scrapie
through a mouse then it is infective in guinea pigs.  (I just made this
specific example up but the concept is correct.)  And don't forget about
Kuru, a CJD-like disease found in New Guinea tribes that practice ritual
canabalism.  And isn't CJD transmitted by pituitary extracts in humans?

Bottom line: Humans *are* susceptible to brain-prion disease transmitted
by eating infected brain matter.  The unknowns are, brains from which
species are infective?  and is non-brain tissue infective?  My semi-informed
guess is that muscle meat (steak, etc.) does not contain the prion
and is non-infective.  

How many Brits have eaten cows brains?  Not many, unless it goes into
sausage (egad).  Can cow prions infect human brains?  Unknown at this
point, and impossible to determine experimentally because of the host
transmissibility problem.
 
-- 
Tom Thatcher                          | You can give a PC to a Homo habilis,
University of Rochester Cancer Center | and he'll use it, but he'll use it
ttha at uhura.cc.rochester.edu           | to crack nuts.



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