1.   Animals contract the infection by eating feed that has been supplemented by the tissues of other infected animals.

2.   That a chicken eating poisoned feed in Belgium could foul wedding cakes in Singapore is yet another reminder of how borderless the global economy has become.

3.   But cows can catch the illness by eating feed made from the parts of infected cows or certain other animals.

4.   But scientists now fear sheep could get BSE from eating feed containing tainted cattle organs.

5.   Many scientists believe cattle got BSE from eating feed containing the ground up remains of sheep infected with the brain-wasting disease scrapie.

6.   Scientists suspect cattle first developed BSE after eating feed containing ground-up organs from sheep suffering from a similar disease called scrapie.

7.   Scientists believe cattle got the disease from eating feed enriched with sheep protein, including organs and nerve tissue.

8.   Scrapie is not believed to pose risks to humans, but scientists now fear sheep could get BSE from eating feed containing tainted cattle organs.

9.   Scientists believe that cattle became infected from eating feed enriched with ground up organs and nerve tissue from sheep.

10.   Scientists suspect cattle first developed BSE after eating feed that contained ground-up organs from sheep suffering from a similar disease called scrapie.