Bern convention on the conservation of European wildlife and natural habitats - Tuberculosis in cattle and badgers
Report by the United Kingdom government
Introduction
1. At the 19th meeting of Standing Committee of the Bern Convention held in Strasbourg from 29 November to 3 December 1999, the UK Government agreed to provide annual reports to the Committee covering all aspects of its strategy and programme to control bovine TB in cattle, including the badger culling trial and its efforts to examine and develop alternative solutions. In particular, the reports were to address the rate of progress with the culling trial and other measures, including vaccines; the number of badgers killed and the impact on local populations; and progress with research into the impact of the trial on other fauna and flora.
2. This paper provides the annual report for the 20th Standing Committee meeting to be held from 27 November to 1 December 2000, and follows on from the detailed report given in its previous paper, T-PVS(99)40.
Background - The incidence of TB in cattle in Great Britain
3. The incidence of TB in cattle in Great Britain continues to rise. The trend is illustrated by Table 1 which gives statistics for the number of confirmed new TB incidents in cattle herds and the number of cattle compulsorily slaughtered under EU legislation as TB reactors or contacts:-
Table 1: TB in cattle 1997 - 2000
| Number of herds with new confirmed TB outbreaks | Number of cattle slaughtered as TB reactors/contacts |
|
|---|---|---|
| 1997 | 515 |
3760 |
| 1998 | 740 |
6083 |
| 1999 | 879 |
6890 |
| 2000 | 502 (to May) |
4018 |
4. During 1999 the number of confirmed tuberculosis incidents in cattle herds rose by 19% over 1998, to a total of 879. This represents 2.4% of all tests carried out in unrestricted cattle herds, compared to 2.2% in 1998. In 1999 a total of 2,880,410 cattle were tuberculin tested in 42,656 herds in Great Britain. The testing disclosed 6,023 reactors, which were compulsorily slaughtered along with 867 animals considered to have been in close contact with infected reactors.
5. Although it is too early to compare the 1999 TB statistics with equivalent figures for 2000, provisional figures for January to May 2000 indicate that in the three month period ending May 2000, the number of confirmed new incidents as a percentage of tests on unrestricted cattle herds was between 2.4% and 2.6%. This compares to 2.3% in the same period a year earlier. The graph at Annex 1 shows the underlying trend in the herd incidence of confirmed TB from July 1995 to May 2000.
6. The continuing increase in TB in cattle and evidence of its geographical spread is of major concern to farmers and to the UK Government and reinforces the UK Government's determination to find a sustainable, science-based solution to the problem.
Progress with the Government's strategy
7. The background to the UK's Government's strategy and its evolution from the scientific review carried out by Professor Sir John Krebs in 1997 is set out in paper T-PVS(99)40 presented to the Standing Committee's 19th meeting last year. The five points of the strategy are:
- minimising the risks to public health.
- continuing with regular cattle testing, slaughter of reactors and movement restrictions as required under EU legislation; and considering whether these arrangements can be strengthened.
- development of a vaccine for cattle TB.
- further research to understand better how infection is transmitted.
- carrying out the badger culling trial recommended by the Krebs and Bourne Committees to find out what contribution badgers make to TB in cattle and whether badger culling is effective in reducing TB in cattle.
8. The Independent Scientific Group under Professor John Bourne has developed a wide-ranging epidemiological investigation into TB in both cattle and wildlife, of which the badger culling trial is one part. An extensive package of research has been put in place by the UK Government on the Group's advice, to run in parallel to the trial. The work of the ISG, and its holistic approach towards finding a sustainable basis for future cattle TB control policies, is set out in its Second Report: "An Epidemiological Investigation into Bovine Tuberculosis" published in February 2000. Hard copies have been made available to the Secretariat and can be supplied on request.
9. The following paragraphs summarise progress with the major elements of the UK Government's strategy.
Public Health
10. The Chief Medical Officer and Chief Veterinary Officer reviewed progress on the public health aspects of Mycobacterium bovis TB in January 2000. They confirmed that the levels of infection in humans remain low (about 40 cases per year) and that the management of risk to human health through pasteurisation of milk, cooking of meat and advice on occupational exposure remains appropriate. Advice has been issued to Local Authorities on heat treatment of milk from infected herds, to Consultants in Communicable Disease Control on screening of people in contact with infected cattle and will shortly issue to owners of abattoirs which receive reactor cattle.
Controlling TB in cattle
11. The cornerstone of the UK Government's TB policy is the system of regular cattle testing, slaughter of cattle which react to the tuberculin test and herd movement restrictions laid down in EU legislation. Herds are tested at one, two, three or four yearly intervals, according to the incidence of TB in the area concerned. In 1999, 2,880,410 tests were carried out on cattle. Animals which have moved out of restricted herds are traced and tested for TB to find and deal with any situations where TB has spread through the movement of cattle. In addition, all cattle submitted to abattoirs are examined for signs of tuberculosis and where TB is found the originating herd is traced and tested. In total, cattle control measures are expected to cost about £20 million in financial year 2000/2001, out of the Government's total spending on TB of over £31 million.
12. In September 1999 the UK Government set up a TB Forum, comprising representatives of farming, veterinary and conservation groups, to consider possible new measures to tackle TB in cattle. The Forum has discussed a number of proposals for changes to the present cattle controls and others are still under consideration. So far the following proposals are being taken forward:
- restrictions on cattle movements between the two stages of the tuberculin test
- imposition of movement restrictions if herds are not tested by the due date
- isolation of the M.bovis organism in any mammalian tissue to be reportable
- better information for cattle purchasers about the TB status of cattle.
- feasibility study into the use of the gamma-interferon blood test to detect TB in cattle.
13. In December 1999 the UK Government appointed an independent panel of experts to look into the effects of cattle husbandry on bovine tuberculosis. The Husbandry Panel was chaired by Dr Clive Phillips of the University of Cambridge Department of Veterinary Medicine, and included a dairy farmer, a zoologist and a veterinarian. The Panel took evidence from a large number of interested parties and reviewed the available literature on the subject. Its report was published on 16 May 2000 and is available at the UK MAFF TB website.
14. The Panel's recommendations identified a number of husbandry measures farmers might take to reduce the risk of infection to their cattle, while making clear that the transmission routes for bovine TB are not fully understood. The Government is examining these recommendations in consultation with the Independent Scientific Group and the TB Forum so as to assess which are likely to be effective against TB and practical for farmers. Many of the findings confirm the advice already contained in the Government's advisory leaflets, issued in 1999, but the Government will consider what more can be done to encourage farmers to adopt better husbandry measures in respect of cattle TB.
The research programme
15. A wide ranging programme of Government-funded research on bovine tuberculosis is in place. A variety of research institutions are involved in the programme, which draws on expertise at national and international level. Research spending (excluding the badger trial) is due to rise from £4 million to £5 million in 2001/2, mainly due to additional research on pathogenesis, transmission and diagnosis of tuberculosis in cattle. A list of current research projects is at Annex 2.
(i) Research to better understand the disease in cattle and wildlife
16. A comprehensive epidemiological questionnaire (TB99) is being used on all cattle farms on which a confirmed TB outbreak has occurred since January 1999. In badger culling trial areas, every suspect outbreak, whether confirmed or not, triggers the TB99 survey and farms with no recent TB are also surveyed. Results from the questionnaires will give a comprehensive picture of TB outbreaks in Great Britain and provide valuable information on the factors which may predispose farms to suffer TB outbreaks. Emerging findings are likely to be available in 2001.
17. During 2000 on the advice of the Independent Scientific Group the UK Government initiated a research programme to investigate the pathogenesis and transmission of tuberculosis in cattle. This programme involves laboratory experiments and field studies. The aim is to obtain a clearer understanding of how and at what stage of infection transmission of M.bovis occurs between cattle, and to improve knowledge of the immune responses detected by diagnostic tests so that testing procedures can be improved. This work is of fundamental importance in advancing control of the disease.
18. M. bovis isolates from cattle and wildlife are being studied with a range of novel molecular strain typing methods. These findings, together with those from projects using GIS and mathematical modelling, will add to the understanding of the epidemiology of the disease.
19. A programme to collect badgers killed as a result of road traffic accidents will re-commence in October 2000. A sample of such carcases will be collected in seven counties of south west and west England and examined for TB. This information may be helpful in understanding the underlying prevalence of TB in badgers.
20. Another major area of the UK Government research programme involves studying potential wildlife reservoirs of M.bovis other than badgers. One project involves live clinical sampling of a range of wild mammalian species and is comparing culture with PCR methods. The second is a carcase survey using pathological findings and culture of tissue for M.bovis. Results from this work are not yet available.
21. The report of the independent Husbandry Panel (see paragraphs 13-14 above) also included recommendations on areas for future research, such as examining the genetic base of disease resistance of cattle, quantifying the nature and extent of badger visitation of farm buildings and feedstores, and further investigations on the epidemiology of the disease. The UK Government is considering these recommendations in liaison with the Independent Scientific Group, the TB Forum and other interested parties.
(ii) Vaccine Development
22. Significant progress has been made in the TB vaccine research programme. The major focus of the programme involves the development of a cattle vaccine, although the option of a vaccine for badgers is being retained. The initial approach of developing vaccine candidates is similar irrespective of the target species. A report on work in the period July 1999 to June 2000 has recently been published and is available from the UK MAFF TB website.
23. At present the programme is focussing mainly on developing new candidate vaccines, and assessing them in laboratory small animal models and in cattle. Their performance is to be compared with BCG vaccination. An advantage of working on cattle vaccines is that candidates which show promise in laboratory small animals can then be tested in the natural host species before progressing to clinical trials. Differential diagnostic tests for cattle using peptide antigens which can distinguish vaccinated animals are also being developed in an effort to address the problem of induced tuberculin test sensitivity. In addition, a project on M.bovis genome sequencing and analysis is expected to provide inputs into the vaccine development programme.
24. The UK Government is also undertaking research on the development of potential TB vaccines for badgers. Work is continuing to develop a blood test for TB in badgers which would allow vaccines to be tested in cattle and badgers. Careful consideration would need to be given to the practicality of delivering a TB vaccine to badgers.
25. UK researchers are working in collaboration with leading experts on TB vaccines in other countries, notably in New Zealand and the Republic of Ireland. There is also specific coordination with the WHO/NIH vaccine screening programme for human tuberculosis, by which promising candidates generated in that programme will be forwarded for testing against M.bovis.
The badger culling trial
26. The objectives of the trial are to establish what contribution badgers make to TB in cattle and whether culling them reduces TB in cattle herds. The key features of the trial design were set out in T-PVS(99)40. In summary, these are:
- The trial will take place in ten areas, known as "triplets" because in each case there are three treatment areas each of about 100km². These are proactive culling (where as many badgers as possible are removed, subject to welfare constraints); reactive culling (where badgers having access to farmland implicated in a TB outbreak in cattle are removed); and no culling (survey only).
- Trial areas account for considerably less than 1% of the total area of Great Britain (about 4% of the South West region). No culling is permitted outside trial areas.
- A closed season operates from 1 February to 30 April.
- The method of capture used is cage traps followed by shooting at close range.
(i) Progress with the trial
27. As at 1 September 2000, eight of the ten trial areas have been put in place, with the two remaining areas due to be announced at the end of September. Culling operations have so far begun in five of the eight areas. The number of badgers killed in the trial so far since culling began in December 1998 is as follows:
| Triplet | Number of badgers culled | |
|---|---|---|
| Proactive area | Reactive area |
|
| Gloucester/Hereford | 55 |
25 |
| Devon/Cornwall | 323 |
73 |
| East Cornwall | 246 |
178 |
| North Wiltshire | 602 |
- |
| West Cornwall | 451 |
- |
| Total (as at 25 August 2000) | 1677 |
276 |
This amounts to 1953 badgers at 25 August 2000. The estimated number of lactating sows was 51. For comparison, the badger population of Great Britain is estimated at over 300,000 and annual road traffic casualties amongst badgers at about 50,000. At this stage, the estimate made by Professor Krebs, that about 12,500 badgers might be killed in the trial as a whole, looks unlikely to be exceeded.
28. Participation in the trial by landowners is voluntary and so far the level of cooperation has been high. The Second Report of the Independent Scientific Group showed participation rates of over 80% in the first three trial areas and levels in subsequent areas have been similar. There has been some interference with trial operations by protesters opposed to badger culling, mainly in the form of damage to cage traps and other equipment. However, action by the police and by Government field staff has limited the extent of this disruption and the trial is designed to allow for such factors. The Independent Scientific Group has confirmed to the UK Government that the trial remains on course to produce valid results by the end of 2004, and possibly as early as the end of 2002 if there is a strong association between badgers and TB in cattle.
(ii) Impact on local populations
29. As stated in last year's report, it is estimated that about 20% of the badgers which are available to be trapped in the "proactive" culling areas will be left after the initial trapping. This 80% capture efficiency takes account of the use of cage traps, and limitation of trapping to a 12 day period. Surveys carried out after culling in four of the five areas proactively culled so far are consistent with this estimate of 80%. In one area, Gloucester/Hereford, the capture rate was lower, possibly due to the fact that the field operations took place in January, when badgers are less active. There may also have been a lower population there due to the number of official culling operations in the area concerned in the past.
30. Estimates of badger recolonisation of proactively culled areas have been made using a simple badger population model, based on previous work (Anderson & Trewhella 1985). The assumption made is that culling efficiency is 80% in year 1 and likely to be lower in subsequent years to account for the expected increase in trap-shy badgers. The number of badgers caught during the second year's culling operations in the Devon/Cornwall trial area is consistent with an immigration estimate of 25%.
31. It is apparent from these estimates of culling efficiency and recolonisation that local badger populations will remain viable even after five years of the trial. There will be a significant depression of the badger population in the proactive areas, which will enable the Independent Scientific Group to advise the UK Government on whether badger culling results in a reduction in TB in the local cattle herds. But local eradication of badgers will not occur.
32. External audit of the badger culling trial is ongoing and is looking in particular at surveying for badgers and the humaneness of dispatch. The auditors first reports are due to be published shortly along with the UK Government response and will be available on the UK MAFF TB website.
(iii) Impact on other fauna and flora
33. A five year research project examining the ecological consequences of badger removal is in its second year. Pre and post cull surveys are to be carried out on four selected triplet areas of the trial. Factors to be examined include estimation of fox, rabbit and hare densities based on nocturnal surveys, targeted studies of hedgehogs and the breeding success of ground nesting birds. These are combined with dietary studies of foxes and badgers to provide measures of changes in prey taken and prey numbers in response to the badger culling trial. These data will be used to assess the ecological consequences of the trial and to produce a food web model of the major predator and prey species. Work to date has concentrated on pre-cull surveys, so that at present no information on effects are available. The main effects of badgers on flora include their role as seed dispersers and effects of trampling and nutrient deposition around the setts and latrines. With the exception of trampling, it is considered that other effects of badger removal on flora are unlikely to be apparent within the five year timescale of the work.
Conclusions
34. The UK Government is making progress on all elements of its strategy to tackle TB in cattle. The main focus remains on the regular testing of cattle herds and the associated controls, which will account for about £20 million of the £31 million budget this year. In addition, there is a comprehensive research programme, overseen by the Independent Scientific Group, which contributes to a better understanding of the epidemiology of the disease in cattle and wildlife. This includes work on vaccines, on cattle pathogenesis, on disease transmission, on cattle husbandry, and on other wildlife species, as well as the badger culling trial.
35. The Independent Scientific Group has confirmed that the trial remains on course to provide valid conclusions about the contribution badgers make to TB in cattle and whether badger culling reduces TB in cattle herds. Progress with the trial so far, presented in this report, demonstrates that the number of badgers being culled in trial areas does not threaten the viability of local badger populations. The original estimate that the trial would remove 12,500 badgers in all, out of the total population in Great Britain of 300,000, looks unlikely to be exceeded.
36. The UK Government is firmly committed to the protection of its native badger populations. Its objective is to find a sustainable solution to the problem of TB in cattle which allows healthy cattle and badgers to coexist.
37. We would be happy to receive from other countries any constructive new ideas or research findings relevant to our strategy.
Ministry of Agriculture, Fisheries and Food
London
September 2000
References
1. An Epidemiological Investigation into Bovine Tuberculosis - Second Report of the Independent Scientific Group on Cattle TB (December 1999).
2. TB and cattle husbandry
(191 KB) - Report of the independent Husbandry Panel (May 2000).
3. MAFF tuberculosis vaccines for animals research programme - Report by the Programme Advisor for the period July 1999 to June 2000 (August 2000).
4. Anderson, R.M and Trewhella, W. (1985) "Population dynamics of the badger (Meles meles) and the epidemiology of bovine tuberculosis (Mycobacterium bovis)". Phil. Trans. R. Soc. London.
5. "Tuberculosis in Cattle and Badgers" - Submission by the United Kingdom Government to the 19th Meeting of the Standing Committee to the Bern Convention (T-PVS(99)40 - August 1999).
6. TB Website of the UK Ministry of Agriculture Fisheries and Food: www.maff.gov.uk/animalh/tb.
Annexes
1. Underlying trend in TB incidence.
2. List
of current TB research projects.
Page last modified:
20 December 2005
Page published: 5 February 2003