Over Thirty Months (OTM) Rule Review

Over Thirty Months (OTM) Rule Review

The Royal Society of Edinburgh (RSE) is pleased to respond to the Food Standards Agency Review of the Over Thirty Months Rule. The Vice-President, Sir David Carter, and the Research Officer, Dr Marc Rands have compiled this response, with the assistance of a number of Fellows with expertise in this area.

While bearing in mind the considerable uncertainties which still surround BSE, the Core Stakeholder Group, set up by the Food Standards Agency, has concluded that the results of the risk analysis indicated that the additional public health benefit provided by the OTM rule was small; that the cost of maintaining the OTM Scheme and OTM rule was large; and maintaining the rule was therefore disproportionate to the level of public health protection and that a move to replacing the rule by testing OTM cattle was justified. The Food Standards Agency has worked hard, and with success, to rebuild public trust in the government in respect of food safety. BSE played a large part in the loss of this trust and any changes to the OTM Rule must be considered with extreme care. In reaching a decision about the OTM rule, the FSA Board should not restrict its considerations to the outcomes of the FSA/SEAC risk assessments, the Core Stakeholder Group’s Report, and the Regulatory Impact Assessment. It should also take into account the need to be able to persuade the public that a decision to abandon the OTM rule is in its best interest.

All of the vCJD cases examined to date are homozygous for methionine at codon 129 of the PrP gene (MM). In the general human population, MM homozygosity occurs in about 37%, valine homozygosity (VV) in 11% and heterozygosity (MY) in about 51 % of individuals. MM homozygosity is therefore thought to be a susceptibility factor for vCJD. However, Zeidler and colleagues caution that this does not necessarily indicate that MY or VV individuals will be entirely resistant to vCJD. It is possible, for example, that patients with these alternative genotypes will develop disease after a longer incubation period and perhaps with a different clinical presentation .

The specific issues identified in the consultation paper are addressed below:

Changing from the OTM rule

On 3 April 1996, the UK 30-month Slaughter Scheme ensured that all cattle aged over 30 months at slaughter would not enter the human food or animal feed chains. As time has passed, cohorts of cattle younger than 30 months will have been progressively less likely to have been exposed to infected feed, especially following the introduction of measures to recover meat and bone meal from various sites and to clean and disinfect these sites and equipment. The numbers of calves that might have been infected by maternal transmission will also have decreased; while this reduction in risk may have been enhanced by the selective cull introduced in December 1996, any effect is difficult to predict with confidence.

It is likely but far from certain that the patients who have so far developed vCJD were severely challenged with the infective agent, possibly in their teenage years, and/or that some predisposing factor or factors operated in each case. The likeliest time for such challenges to man was when BSE-infected bovine products had free access to the human food chain, i.e. in the mid-1980s and (sadly) well into the 1990s before control measures were effectively enforced. The likely incubation period of vCJD may be 5- 10 years or more. Since 1995(and awareness of vCJD in man)until May 2003 the total number of cases of definite or probable (including patients still alive) is 135. The annual numbers of deaths since 1995 are 3, 10, 10, 18, 15,28,20, 17, and 8 so far for 2003. It is to be hoped that the annual incidence is declining, but it is much too early to be sure.

The scientific analyses considered by the Core Stakeholder Group use risk assumptions that they regarded as pessimistic, and the conclusions drawn from them are appropriately precautionary. While the cost of the OTM scheme is undeniably great, not everyone would accept the contention that that the public health benefit from the application of the OTM rule in terms of lives saved is barely measurable. It is of interest that our responding Fellows took differing views on the validity of the conclusions reached by the Core Stakeholder Group.. However, on balance the majority of our responding Fellows agreed that it is timely to consider moving to a system of public health protection that relies on implementation of the rules in the EU legislation (which came into force on 1 January 2001) and replaces the OTM Scheme with testing. It is worth emphasising that some of our Fellows expressed unease about the efficiency of testing and it will be important to be able to produce robust data on efficiency if a move to testing is to be made.

However, the crucial factor in reducing the numbers of further cases in cattle is the exclusion from the animal food chain of tissues known to contain the BSE agent. As late as mid-1994, it was estimated that about half of the specified bovine offal materials being processed were not properly separated and could still have been entering rendering plants.

The DEFRA Progress Report of June 2002 indicated that 18 BSE cases had been identified in Great Britain in cattle born after 1 August 1996 when controls were extended and enforced The Report stressed that .."there are no human health implications ...as the animals involved ...were over 30 months of age (and) have all been excluded ...(and) any surviving offspring traced and excluded from human consumption...". Of particular concern to some of our Fellows, the DEFRA Progress Report of December 2002 states that BSE has been confirmed in 33 animals born after 1 August 1996 and that as of January 2003 an animal born in November 1998 is so far the latest-born animal to develop BSE, presumably as a result of contamination of animal feed. These facts taken in conjunction with reports (Meat Hygiene Service) of non-compliance with Specified Risk Material (SRM) and continuing unsatisfactory reports following visits by the State Veterinary Service to a small number premises handling SRM, mean that vigilance cannot be relaxed. Concern is underpinned by reports that approximately 12 suspect cases of BSE in British cattle are still being reported each week.

It is essential that the necessary resources should continue to be provided to underpin surveillance of BSE, CJD and scrapie and the relevant research and advisory services must be sustained over the next two decades. It is also imperative that control measures are rigorously enforced in the UK and abroad.

The options

In order to build and retain public confidence in the regulatory system, and in British beef, any alternative to the OTM Rule should be introduced only after great care and with great circumspection. Opinion surveys show that the British public continues to have great interest in and residual concerns about BSE and vCJD, particularly as cases of the vCJD are expected to continue to appear because of the long incubation period. The OTM scheme has been described many times as an essential part of the belt-and-braces approach to public protection in place since 1996, but as outlined above, the scheme has not eradicated BSE from British cattle or removed all concerns about the enforcement of existing regulations.

Any change cannot be contemplated until safeguards to ensure effective enforcement are demonstrably in place and the Core Group’s implementation provisos have been met. While some of our Fellows do not feel that we are yet in a position to relax or remove the OTM Rule, most of our respondents take the view that change can now be contemplated. If change is introduced, the most precautionary of the proposed alternatives should be followed, namely to allow cattle born after a specified date into the food supply. It would be preferable to use a birth date option of October 1999, rather than August 1996, (because of its clear association with improved traceability, tagging and robustness of the cattle passport scheme) and allow a year for the British Cattle Movement Scheme (BCMS) to be properly implemented. While we appreciate the immense financial cost to society of maintaining the OTM rule, we can foresee formidable difficulty with public acceptance of an economic argument for the introduction of alternative schemes, We understand the utility of the VPF (value per fatality) but would urge caution in its application to an emotive subject such as vCJD.

Enforcement and Implementation

For cattle, the individual cattle passports and the movement recording system (BCMS), which was introduced in 1998, proved effective and valuable. However, the present ear tagging system is not foolproof, and susceptible to fraud. A system of inserting microchips or electronic devices that cannot be tampered with would go some way toaddress this.

Further risk reduction measures

The only area not covered in the report relates to the need for a validated diagnostic test for BSE in cattle going to market. In the absence of such a test, precautionary measures have to be rigorously implemented.
In addition, the potential for dorsal root ganglia to remain when the vertebral column is removed should be investigated further and OTM casualty cattle should be excluded from the food chain.


In conclusion, most of our responding Fellows agree that it is timely to consider replacing the OTM Rule with testing. It must be emphasised that some of our respondents do not consider that conditions are yet in place to allow relaxation or replacement of the OTM Scheme. If testing is adopted it will be imperative to ensure that control measures are rigorously enforced in the UK and abroad, and to postpone change until safeguards are demonstrably in place to ensure effective enforcement and satisfy the implementation provisos of the Core Group. If the OTM Rule is to be replaced the preferred option would be to restrict access to the food supply to cattle born after October 1999 because of the demonstrable link to improved traceability, tagging and robustness of the British Cattle Movements Service cattle passport scheme introduced in 1998. The validity of the October 1999 deadline would of course require review if a cow born after October 1999 were to be shown to be another case of BSE. If the OTM rule is replaced it will be advisable to allow a year for the scheme to be properly implemented and so help allay National Farming Union fears that the market could be overloaded with beef.

Additional Information

In responding to this consultation the Society would like to draw attention to the following Royal Society of Edinburgh publications which are of relevance to this subject: The Scottish Executive's Interim Response to the Findings of the Phillips Report of the BSE Inquiry (May 2001); Inquiry into Foot and Mouth Disease in Scotland (July 2002) and Preparing an Animal Health and Welfare Strategy for Great Britain (April 2003). Copies of this response and of the above publications are available from the Research Officer, Dr Marc Rands or from the RSE web site: www.royalsoced.org.uk.


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