EVEN animals that don鈥檛 become ill after being infected with the 鈥減rions鈥�
thought to cause BSE, scrapie and similar diseases can have enough of the
proteins in their tissues to infect others, new research confirms. The finding
raises again the possibility that animals such as pigs and chickens, which ate
feed thought to be tainted with BSE prions, could harbour the infection
(This Week, 6 April 1996, p 5).
Richard Race and Bruce Chesebro of the National Institute of Allergy and
Infectious Diseases in Hamilton, Montana, infected mice with a strain of hamster
scrapie thought not to cross this species barrier. The mice didn鈥檛 get ill. But
tissue from their brains and spleens gave hamsters scrapie if it was injected
into these animals鈥� brains (Nature, vol 392, p 770).
Britain鈥檚 Spongiform Encephalopathy Advisory Committee (SEAC) is concerned
about hidden reservoirs of BSE. 鈥淚t鈥檚 something that I鈥檝e been worried about for
some time,鈥� says John Collinge of St Mary鈥檚 Hospital, London, a SEAC member.
Typically, only one or two cows in a herd get ill when all have eaten the same
feed. Potentially, many of the others could be silently harbouring the
infection.
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A spokesman for Britain鈥檚 agriculture ministry says that plans to survey the
brains of healthy slaughtered cattle for BSE prions are being discussed. But
there are no current plans to see whether tissues from pigs and chickens can
transmit BSE to cows.