TB in meat

Tuesday 10 February 2004

This paper updates the Board on recent developments in relation to the risks associated with TB in meat, in particular the results of FSA-funded research, and further advice from both ACMSF and EFSA.

Issue

1. TB in cattle continues to be a growing animal health problem for DEFRA and the farming community, and with potential implications for food safety and public health too.

Background

2. In September 2000, the ACMSF was asked by the FSA to review the possible human health risks associated with the consumption of meat from cattle with evidence of Mycobacterium bovis infection, including animals with no post mortem evidence of disease which had reacted positively or inconclusively to the tuberculin test. The Committee was also asked to advise on the adequacy of current control measures.

3. The ACMSF assessed the risk to consumers from eating meat from M. bovis-infected cattle following Meat Hygiene Service assessment and action at abattoirs as very low. However, ACMSF made a number of recommendations designed to improve hygiene procedures in slaughterhouses, and to bring UK meat inspection requirements fully into line with EU legislation.

4. In addition, two risk management options were suggested by ACMSF to the FSA as a means of reducing the very small potential risk still further. First, it was suggested that meat from reactor cattle with visible local lesions, or from cattle found to have localised tuberculous lesions on routine post mortem inspection, should no longer be permitted to be sold as fresh meat even though the area containing any lesions had been removed but should instead be required to be heat treated and go for manufacture.

5. A second option proposed for consideration was that carcasses from reactor cattle with no visible lesions (NVL) should be required to be held in cold storage pending receipt of culture results. Those carcasses microbiologically-confirmed as M. bovis-positive would be either partially or wholly condemned.

6. In December 2001 the FSA Board noted the outcome of the ACMSF review and agreed that the Agency should change abattoir practice to align with EU requirements. In addition the Board noted that the heat treatment option was then currently under consideration by the European Commission and thus decided to await the outcome of deliberations in Brussels. Those deliberations concluded that a decision on heat treatment should await a risk assessment being made by the European Food Safety Authority.

Abattoir Practice

7. In line with ACMSF’s recommendation to change abattoir practices and to bring UK meat inspection requirements fully into line with EU legislation, revised and up-dated instructions on the handling and inspection of reactor, inconclusive reactor and direct contact cattle were issued to MHS staff in October 2002, following discussion and agreement with DEFRA. The instructions make clear that where post mortem inspection reveals localised tuberculous lesions in more than one organ or area of the carcase, then the whole carcase and its offal and blood should be declared unfit for human consumption. Where, however, tuberculous lesions are found only in a single organ or part of the carcase, the instructions require the removal of the affected organ or part of the carcase as unfit for human consumption. In addition, to minimise the opportunity for cross-contamination of ‘clean’ animals, all reactor / inconclusive reactor / direct contact animals must now be processed at the end of the day, following which the slaughterhall must be subject to full cleansing and disinfection.

On-farm situation

8. In recent years the level of bovine TB in British cattle has continued to rise, despite efforts to contain the disease. In 1996 the numbers of animals reacting positively to the tuberculin test and subsequently compulsorily slaughtered by the Agriculture Departments was just over 3,100. By 2000 this figure had risen to a little over 7,000, and in 2002 the number was almost 20,000, although the latter figure was somewhat higher than it might otherwise have been, following a drop in TB reactor slaughterings in 2001 on account of FMD. Nevertheless, in the 10 months to October 2003, some 17,000 reactors have been compulsorily slaughtered. It should be noted however that the majority of reactor animals are more than 30 months old and are therefore excluded from the food chain by virtue of the OTM rule.

FSA funded research

9. Following the ACMSF review, the FSA commissioned a study to investigate whether M. bovis was present in the edible tissues of salvaged carcasses from cattle which had reacted positively to the tuberculin test or showed evidence of M. bovis infection at post mortem meat inspection. The Agency study was carried out on the carcases of cattle aged over 30 months that had reacted to the tuberculin test. None of these cattle entered the food chain, but, if they had been less than 30 months old, those that had no visible lesions (NVL) or only a single visible lesion would have been considered fit for human consumption.

10. A total of 143 reactors were sampled and two sets of lymph nodes from each animal were cultured for M. bovis. One set consisted of the lymph nodes draining the major muscle masses of the carcase and the liver, and the other those draining the head and lungs. Muscle itself was not sampled as the literature confirmed it would be very unlikely to yield positive results in the relatively small number of carcases sampled. A total of 19 of 110 NVL animals (ie 17%) were positive. From 5 (4.5%) of these M. bovis was cultured from the lymph nodes draining the carcase and liver, which remain attached to carcases and offal when they are sold for human consumption. One of 25 (4%) of VL animals with a single lesion, and 1 of 18 (5.5%) VL animals with two or more lesions, yielded M. bovis from lymph nodes draining the carcase and liver.

Further opinion of ACMSF

11. ACMSF based its original recommendations on the assumption that up to 10% of NVL carcases would be culture positive. As noted above, the FSA research showed that some 17% of such carcases were positive. ACMSF considered the results of this further work in September 2003. It concluded that the results did not alter the outcome of its previous risk assessment, since this was based on the epidemiology of infection in humans and was not affected therefore by demonstration of a slightly higher occurrence of M. bovis in carcases than had been originally assumed. The Committee did however agree that fresh attention should be drawn to its previous recommendations to maintain enhanced surveillance and to alert the FSA to any significant indications that eating meat from M. bovis infected cattle constituted a health risk. It also agreed to recommend to the Agency that it should review its decisions on the heat treatment option and the proportionality of the cold storage option.

Opinion of EFSA

12. As mentioned in paragraph 6, the European Commission and Member States agreed that a decision on whether or not meat from reactor animals with no or just a single lesion suspicious of tuberculosis should be heat treated should be deferred, pending a risk assessment being carried out by EFSA.

13. That assessment was adopted in November 2003, and took account of the results of the FSA funded research. EFSA concluded that taking account of the low prevalence of M. bovis in the human population, there was no evidence available to suggest that additional restrictions on the use of beef from tuberculin reactor cattle would contribute to the prevention of human cases of tuberculosis due to M. bovis. Any change to EU rules in the short term, or scope for Member States to act unilaterally in this area eg to require heat treatment of meat from TB reactor animals, would therefore appear unlikely. Moreover, the EFSA opinion supports the Board's previous view that it was not proportionate to require suspect carcases to be held in cold storage pending receipt of culture results.

Board action required

14. The Board is invited to:

• note the changes made to abattoir and meat inspection practices;
• note that both ACMSF and EFSA have concluded that the risks to public health through the consumption of meat from TB reactor animals are very low; and
• note that EFSA is not recommending any changes to existing meat hygiene controls.