THE BSE food scandal just won鈥檛 go away. New evidence again raises the possibility that the disease may have spread among Europe鈥檚 sheep flocks.
Sheep develop a disease similar to BSE (mad cow disease) if they eat infected cattle tissue. Now Sue Bellworthy and colleagues at the UK鈥檚 Veterinary Laboratories Agency (VLA) have shown that BSE can also be inherited in sheep. They report that two ewes experimentally infected with BSE in 2000 gave birth to lambs in 2003 that died of BSE this year (The Veterinary Record, vol 157, p 206). It is the first confirmation of 鈥渧ertical鈥� transmission from mother to lamb before or during birth 鈥� something suspected but never proved in cattle.
Feeding cattle remains to sheep was banned in the European Union in 1994, and any sheep infected that way should have died by now. But the new finding means that BSE could have passed to future generations. And because BSE symptoms in sheep resemble the common, related disease called scrapie, 鈥渕ad鈥� sheep could have remained undiagnosed.
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In the UK nearly 2700 sheep that appeared to have scrapie have been tested for BSE. None has shown clear-cut BSE, though two are being tested further. 鈥淰ertical transmission would be limited to one family line which would die out as animals succumb to BSE or are eaten, says Danny Matthews, a BSE expert at the VLA.
But can sheep transmit BSE horizontally to other animals? There is no evidence yet this has happened, but if it can, it could have made the difference between the disease dying out and spreading far more widely.
