杏吧原创

FIRST it was beef, now it is lamb. The fallout from the BSE health scare
seems set to taint the entire British meat industry.

Last week, to quell fears that people might be at risk of contracting
Creutzfeldt-Jakob disease (CJD) from sheep, agriculture minister Douglas Hogg
proposed a ban on the sale of sheep鈥檚 brains. His move followed the
discovery by
scientists in Edinburgh that BSE can be transmitted from cows to
sheep鈥攅ither by injecting infected cow brain tissue into the animals
or by
forcing them to eat the material.

Anyone who has followed the BSE story from the early days will see that we
have come full circle. In the late 1980s and early 90s, the then agriculture
minister John Gummer had a soothing message for anyone concerned that BSE might
cross the species barrier and infect humans who ate beef products.
Epidemiologists at Gummer鈥檚 ministry had concluded that BSE arose when cattle
were fed the remains of sheep suffering from scrapie, a disease similar to BSE
that has been endemic in the British flock for more than 200 years. For
generations, people have eaten lamb without going down with CJD, Gummer
reminded
us, so BSE is unlikely to be dangerous. But as a precaution, the consumption of
cow brains and certain other bovine offals was banned.

Now Hogg tells us that while BSE can be passed from cows to sheep under
experimental conditions, there is no evidence that BSE has actually turned
up in
the British flock. 鈥淭here is no direct threat to human health,鈥� he announced
last week, only 鈥渁 theoretical risk鈥�.

Clearly, the official view now is that BSE is different from scrapie. For if
BSE is merely scrapie in cows, as Gummer earlier suggested, the disease is
already present in British sheep. The revised view is much more
reasonable: some
scientists believe that BSE has nothing to do with scrapie
(This Week, 13 April, p 4).

Once again, however, the government is putting its own spin on scanty
scientific knowledge. It is true that there is no evidence that British sheep
are affected by BSE. But if small numbers of them were, we probably wouldn鈥檛
have noticed. The only reliable way of distinguishing BSE from scrapie is to
examine its incubation period and effect on the brains of lab mice.

The facts are that we don鈥檛 know where BSE came from and we can鈥檛 be sure
whether it has spread from cows to sheep. The likelihood of contracting
CJD from
sheep offal is probably extremely low鈥攊n Britain, after all, few people
eat sheep鈥檚 brains. But to state categorically that sheep pose no threat to
human health is as misguided as the earlier message that BSE is merely our old
friend scrapie.