Volume 5: Animal Health, 1989-96
4b. Implementation, enforcement and monitoring of the animal SBO ban: discussion
The effectiveness of the ban
The significance of the BABs

4.595 When the animal SBO ban was introduced, the ruminant feed ban (RFB) was already in place. It was forbidden to feed any ruminant protein to cattle, so there should have been no question of cattle feed including any ingredient derived from bovine tissue. The SBO ban was introduced in order to address the risk that non-ruminant animals might be infected with BSE as a result of eating infective tissue derived from an animal infected with the disease.

4.596 The ban aimed to ensure that animals generally were protected against the risk that cattle tissues might be capable of transmitting BSE orally. Humans were already protected against this risk by the human SBO ban. Now bovine tissues which might carry sufficient infectivity to give rise to a risk of transmission would be excluded from animal feed. The evidence set out in this chapter shows that this aim was not achieved.

4.597 Had pigs or poultry or other non-ruminant animals proved susceptible to oral transmission of BSE, the success of the animal SBO ban would have been gauged by the extent to which such animals succumbed to the disease. Happily, these animals have not proved susceptible to oral transmission. The failure of the animal SBO ban has been demonstrated in an unexpected fashion - by the birth of BABs (victims of BSE born after the RFB came into force). Of significance in the present context are those BABs born after the animal SBO ban came into force.

The significance of the BABs

4.598 The Inquiry has been particularly concerned with the implementation of the animal SBO ban in relation to the SBO that was sent to renderers. This is because there were shortcomings in the implementation of the ban in this area which had serious consequences. Those consequences were not the infection of the animals that the SBO ban had been designed to protect. So far as we are aware, no non-ruminant farm animal has been infected with BSE as a result of the inclusion in its feed of meat and bone meal (MBM) contaminated by SBO.

4.599 What occurred was something that had not been foreseen when the animal SBO ban was introduced. Animal feed for non-ruminants, which contained ruminant protein, contaminated feed for ruminants, which should not have contained this protein. Some of the protein contained the BSE agent, and the contaminated feed transmitted BSE to some of the cattle to which it was fed.

4.600 This cross-contamination occurred in feedmills which produced feed both for ruminant and non-ruminant animals. It may also have occurred in transit and on farms where farmers mixed their own feed for their animals, or where the same equipment was used when handling feed for different types of animals. The ruminant protein that contaminated the cattle feed was MBM, produced and sold by renderers for incorporation in feed for non-ruminants. Had the animal SBO ban operated as intended, this MBM would not have been derived from material that included SBO and would not have been potentially infective.

4.601 The statistics of the BABs, and more particularly those born after the animal SBO ban came into force, give some indication of the extent to which infective material was being incorporated by renderers in the MBM which they were producing. Over 11,000 BABs were born after 25 September 1990 when the animal SBO ban came into force.

4.602 These figures are a startling indictment of the efficacy of the animal SBO ban. MAFF's epidemiologists concluded that only a small proportion of BABs can have resulted from maternal transmission. Most of them resulted from cross-contamination of cattle feed with feed prepared for non-ruminant animals (see vol. 2: Science).

4.603 The scale of infection is the more remarkable, when one considers the following facts:

1. For every cow which lived to develop clinical symptoms several must have been infected, but slaughtered before the symptoms developed.
2. The contaminant matter will have been subject to the rendering process, and thus:
   1. to a degree of inactivation
   2. to dilution with non-infective material.
3. The contaminant matter will have been further diluted by incorporation, as a result of cross-contamination, into ruminant feed containing no animal protein.

4.604 A further remarkable feature is that almost all the infective material must have originated from subclinical animals. The evidence considered in vol. 6: Human Health, 1989-96, Chapter 2 indicates that few animals showing clinical symptoms will have escaped compulsory slaughter and destruction. The wisdom of the human SBO ban is clear.