R.Burge at bay.cc.kcl.ac.uk (Richard Burge) writes:
>In article <1994Apr18.130804.52291 at ucl.ac.uk>...
> ... spbcnsp at ucl.ac.uk (Mr Neville Steven Percy) (ME!) writes:
>>No one expected anything like the transmission of Scrapie to cows, Prion
>>diseases had never previously crossed the species barrier...
>How do you know? Are you telling me that you can definitively state that CJD,
>GSS, Kuru, Bovine, Mink and Feline Spongiform encephalopathies and all the
>others arose spontaneously in the individual species?
Well I meant it had never been known to cross the sp. barrier:
GSS is genetic.
CJD is 15% genetic, and although admittedly to say that the 'sporadic' 85% is
down to somatic mutation seems extreme, there was never any reason to
suspect a cross-species transmission.
Kuru is very much like CJD, and derives (derived, there're only about 10 cases
left, I think) from cannibalism which has now been eliminated.
TME (Transmissible Mink Enc.) and FSE (Feline Spong. Enc.) both date from after
the outbreak of BSE, rather than having ever been arisen from Scrapie-
infected sheep. Likewise all the exotic antelope diseases in Kudu and
Oryx and things.
These didn't arise in the individual species, only humans (with a very long-
lived CNS) and sheep ever seem to have acquired the spontaneous disease. All
the rest seem acceptably traceable to the infected beef/bonemeal. Either the
putative change in the agent on crossing the sp. barrier into cows made it much
more nasty, or beef is treated/distributed differently to mutton.
Nev Percy ; spbcnsp at ucl.ac.uk