But it can pass the infection to another species, which then falls sick. There has been, for example, no visible outbreak of TSEs, the group of diseases that include BSE, in pigs and chickens. Researchers working for Britain's Ministry of Agriculture, Fisheries and Food have failed to cause disease in pigs and chickens by giving them BSE-contaminated feed. This may mean such meat is safe. Crucially, however, no one has reported putting tissue from pigs or chickens that ate BSE-contaminated feed back into cows or other animals, to show if they are nonetheless infectious.
Sheep are another matter.
When they eat BSE-contaminated feed, they develop a disease clinically similar to the sheep disease scrapie. So these sheep still have BSE, which, unlike scrapie, is a potential human pathogen. Scrapie is common in much of Europe. We would not realise such sheep were dangerous, so people could be eating animals that are infected but not yet sick. It has taken a while for researchers to realise the risk.