Sir: We are told that BSE is a form of scrapie that entered the cattle population through feed contaminated with infected sheep offal. If this is the case, then obviously the disease can cross between species and, therefore, potentially infect humans. The difficulty with this hypothesis is that there is no need to postulate cattle as an intermediate step. Scrapie has been endemic among the sheep population for generations, and if it were going to cross species with any ease, then we should have heard much more about mad sheep disease in the past, and the incidence of Creutzfeldt- Jakob disease would be much greater.
The question that this generates can be phrased in two ways. If it is safe to eat sheep, then why should it not be safe to eat cattle? Alternatively, if there is a risk involved in eating cattle, why is the risk not even greater in eating sheep?