IF THERE is one categorical pronouncement you can safely make about prion
diseases like BSE or CJD, it is that one should not make categorical
pronouncements. “British beef is safe” and “there is no BSE in Germany” come to
mind. Now there are two more: “scrapie is safe”, and “people don’t catch
sporadic CJD”. Scrapie is the most widespread prion disease, infecting untold
numbers of sheep worldwide. Sporadic CJD is the old-fashioned pre-BSE kind that
is supposed to happen spontaneously in unlucky people. But a surprise
observation in France suggests some sCJD cases—though by no means
all—may be linked to scrapie after all
(see p 4).
For years, British authorities asserted that BSE was harmless because it was
a form of scrapie. In fact, the only evidence scrapie is safe is some
broad-brush epidemiology, good as far as it goes but unable to reveal occasional
risks for some people from some sheep. Alarm bells should have rung in 1980 when
researchers gave monkeys scrapie by feeding them infected brains. But that
research, like so much other work on prion diseases, was never followed up. We
still have little idea what BSE does in pigs and chickens. The Queniborough vCJD outbreak
(see p 5)
would be easier to understand if we knew how much brain we
must eat to be infected. As for scrapie, it shouldn’t take a chance finding to
tell us that there may be dangerous sheep out there.
