HL Deb 15 July 1996 vol 574 cc46-7WA
The Countess of Mar

asked Her Majesty's Government:

Whether there has been demonstrated a causal relationship between scrapie infected feed and BSE by exposing a test herd of cattle under controlled conditions to the infected feed; and if so, what were the results; and, if not, why not.

Lord Lucas

Calves have been fed brain from clinical BSE cases in a number of studies, and the challenged cattle have developed BSE. The experiments used unprocessed brain rather than animal feed as a source of infection but demonstrated quite clearly that cattle can develop BSE by being fed infected material.

Experiments in the USA have shown that inoculation of scrapie infected material into cattle causes clinical signs and lesions that appear not to be identical to those of BSE. There are a large number of different scrapie strains, and those in the USA may not be the same as in the United Kingdom. The experiment described does not prove either way whether BSE originated from scrapie or not. There are at least four possible hypotheses:

  1. (a) that BSE originated from a particular strain of scrapie found in British sheep (and possibly not found in the USA) which was particularly well suited to causing disease in cattle once exposure occurred through contaminated feed;
  2. (b) that BSE was caused by a scrapie strain which adapted to cattle;
  3. (c) that BSE is unrelated to scrapie and has been a cattle agent for a long time, occurring at a very low level which either never caused clinical disease of caused clinical disease so rarely that it was not recognised until changes in rendering practices resulted in greater exposure of cattle to the agent in feed.
  4. (d) that BSE arose from a mutant strain of scrapie which infected cattle more readily than most strains—this does not fit the epidemiological data.

An experiment similar to that conducted in the US has not been undertaken in the United Kingdom because it was not judged to be of sufficiently high priority in relation to other research objectives. Although interesting, the result would not have given useful information in relation to the control of the disease.