ARCHIVE: BSE: Disease control & eradication - the feed ban - born after the July 1988 ban (BAB) cases

[back to The feed ban]

The July 1988 ban on feeding ruminant proteins to ruminants (e.g. cattle, sheep, goats and deer) in Great Britain, significantly reduced the risk of BSE infection. There was a marked decrease in the number of confirmed BSE cases born after the July 1988 ban (BAB cases) although the long incubation period delayed the impact on BSE cases by approximately five years. Investigations of the initial BAB cases indicated that the most likely source of infection in these cases was the continued use of feed manufactured before the 1988 ban.

Reasons for BAB cases

By autumn 1994 the decline in the epidemic was occurring more slowly in the north and east of England in which the proportion of pigs relative to cattle was highest. At that time pig and poultry feed could legitimately contain ruminant meat and bone meal (MBM) and there was an increased risk of cross contamination of cattle feed with MBM in these areas. Samples of cattle feed taken in August 1994 were found to contain ruminant MBM, demonstrating that such cross-contamination could occur. A 1994 case-control study looked at possible causes of BSE in BAB animals concluding that a food borne source of infection was the most likely explanation.

The continued presence of BSE infectivity in MBM suggested failings in the Specified Risk Material (formerly Specified Bovine Offals (SBO)) controls. The most likely source of this problem came from the practice of splitting bovine skulls. Brain was disposed as SBO and the skull was rendered to MBM, but brain tissue sometimes remained in the skull, allowing infectivity to enter MBM. Other SBO may have been inadequately separated from non-SBO material, providing another potential route of infection. Subsequent research has shown that some of the rendering systems in use until December 1994 had little effect on BSE.

Prevention of Cross Contamination

In August 1995, the controls on the handling of SBO were strengthened further to protect animal health. They required that the whole skull (except the tongue) be disposed of as SBO and that rendering plants use dedicated lines for processing SBO. In April 1996 the use of mammalian MBM was banned in all feed for livestock, fish and equine animals. This was not as a result of fears of BSE in non-ruminant species but to remove any possible risk of cross-contamination of cattle rations with MBM in feed intended for other species. A Voluntary Feed Recall Scheme, in June 1996, offered free collection and disposal of residual stocks of feed. From 1 August 1996 it became an offence (except in very tightly defined and controlled circumstances) to hold mammalian MBM on farms or in feed mills and premises where livestock feed is used, produced, prepared or stored.

BSE: Disease Control & Eradication - The Feed Ban - Born After the Reinforced Ban (BARB) Cases

1 August 1996 is regarded as the date the reinforced feed ban became effective. BSE cases born after July 1996 are referred to as born after the reinforced ban (BARB) cases.

Incidence

Details for cases in animals born after the reinforced feed ban of August 1996, that have been confirmed in Great Britain and in Northern Ireland, are available on the Veterinary Laboratories Agency website (PDF 300 KB).

Reasons for BARB Cases

Animal Health carries out a detailed epidemiological investigation into all BARB cases in Great Britain. One possible reason for BARB cases is the contamination of cattle feed ingredients with mammalian MBM handled, stored and transported outside the UK, prior to the 2001 EU-wide ban feeding of processed animal protein (PAP) to all farmed animals. Newer Member States may not have implemented full BSE controls until after January 2001.There is also evidence from epidemiological investigations into BARB cases that some cases result from the persistence of infection in feed stores.

In 2004, Professor William Hill FRS of the University of Edinburgh carried out an independent review of BARB cases in the UK. Professor Hill concluded that the UK controls in place to eliminate BSE in cattle were soundly based and confirmed that the elimination of food-borne sources was key to the eradication of BSE. He recommended that risk-based controls and monitoring should be maintained on animals and feed.

The report is available (PDF 177 KB) and the Defra response is available here (PDF 55KB).

Multiple Cases and the South West Wales Cluster

A small number of herds have generated more than one BARB case (PDF 50KB). Most of these natal herds are located in South West/ West England or South West Wales. These findings suggest a common feed source during the first 12 months of life in the affected herds. Reports of the investigations into herds generating the cluster of BARB cases in South West Wales and into herds experiencing multiple BARB cases are available below:

Persistence of the BSE Agent in Feed Stores

Investigations into herds experiencing multiple BARB cases indicate that some of these cases might have resulted from the persistence of infection in farm feed bins. We believe that the current risk of BSE infection to cattle as a result of the persistence of the BSE agent in farm feed bins, from feed produced before either the 1996 UK feed ban or the 2001 EU feed ban, is extremely low. Nevertheless we recommend that cattle keepers clean out feed bins routinely and very thoroughly, particularly those feed bins which were in use before August 1996 and have not been cleaned out since. This is especially important for herds which have experienced homebred BARB cases or multiple BARB cases. Specialist contractors and/or equipment may be required to clean the inside of feed bins.

Position in Other Member States

Several other EU Member States have had one or more BSE cases confirmed in cattle born after the 2001 EU-wide feed ban.

 

Page last modified: 3 September 2010
Page last reviewed: 10 September, 2006