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Public Health and Bovine Tuberculosis: What's All The Fuss About?

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Paul R. Torgerson and David J. Torgerson believe policy needs to change. They are authors of the report published in November 2009, Public Health and Bovine Tuberculosis: What's All The Fuss About? In their report they propose that bTB control in cattle is irrelevant as a public health policy. They provide evidence to confirm that cattle-to-human transmission is negligible. They also state that aerosol transmission, the only probable route of human acquisition, occurs at inconsequential levels when milk is pasteurised, even when bTB is highly endemic in cattle. Furthermore, they believe there is little evidence for a positive cost benefit in terms of animal health of bTB control. Such evidence is required; otherwise, there is little justification for the large sums of public money spent on bTB control in the UK.

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The skin test has many problems so why is a vaccine not yet being used to control the spread of bovine TB?
“The best prospect for control of TB in the British herd is to develop a cattle vaccine” – Krebs Report (1997).

According to Defra (www.defra.gov.uk/foodfarm/farmanimal/diseases/atoz/tb/research/vaccine.htm) Developing a TB vaccine for badgers and cattle is a long-term goal and a substantial part of the Defra research programme focuses on this. Total investment (since 1998) in vaccine development reached more than £17.8 million by the end of March 2008. Over £5.5 million was invested in cattle and badger vaccine research in 2007/2008. We are told that real progress has been made yet a vaccination for cattle is STILL not available as efforts have, instead, been concentrated on a vaccine for badgers.

'Options for vaccinating cattle against bovine tuberculosis' published by Defra, indicate that cattle vaccination is a viable option for the control of bTB. (Ref. 2)

Bacteria which causes TB is always in the environment and all animals are susceptible – not just cattle and, so it is highly unlikely it will ever be eradicated. The TB policy and the nightmare of testing is becoming increasingly difficult for those who keep cattle therefore vaccination would seem to be the most logical course of action.

Despite a compulsory TB testing regime for cattle over the last 50 years with huge amounts of taxpayers’ money spent on research, testing and associated costs, official statistics claim that it is still spreading. In fact, bovine TB is apparently now ‘endemic’ in the South West of England, the West Midlands and Wales’ . Interestingly, physical clinical symptoms of TB are still very rarely seen in any animal.

The bovine TB status of an area is based on the results of the intradermal tuberculin (skin) test and the number of animals slaughtered as reactors and inconclusive reactors. However, there is a great deal of debate regarding the reliability of the existing skin test. Indeed it is clear that the test and slaughter policy is killing many cattle that are unlikely to be infectious and which do not have the disease. A significant percentage of reactors and inconclusive reactors, slaughtered under the existing system, reveal no evidence at all of bovine TB on post mortem (either lesions or after tissue culture). DEFRA attempts to convince everybody that all cattle slaughtered under the policy posed a risk, whether or not lesions are found or tissue culture is positive, yet they give no scientific evidence to add plausibility to such claims. It is likely many of these animals would never have developed any symptoms, would not become infectious and would have continued to lead a healthy life.

Bacteria which causes TB is always in the environment and all animals are susceptible – not just cattle and, so it is highly unlikely it will ever be eradicated. Perhaps we should therefore aim to control it. The TB policy and the nightmare of testing is becoming increasingly difficult for all those who keep cattle therefore vaccination would seem to be the most logical course of action. Surely if we can and have controlled the human form of TB without killing and culling, why can't we do the same with bovine TB? It is accepted that the BCG vaccination is not perfect and will not give perfect protection but it is likely to be comparable, in terms of efficacy, with the existing procedure and give sufficient control of the disease.

The total spent (since 1998) on vaccine development for the UK has reached more than £23 million. In 2008, Hilary Benn committed a further £20 million to be spent on vaccine development with the aim of strengthening the prospects of successfully developing a usable vaccine. The only licensed vaccine for bTB is Bacillus Calmette-Guerin (BCG). This is inexpensive and rated as one of the safest vaccines ever developed. In humans and cattle it has moderate efficacy, providing partial protection against M bovis (Ref 1.) ) It reduces risk of infection by 50% and death by 70%, so would appear to be as effective as the existing skin test policy is. The only problem is that vaccinated animals show up as positive reactors when tested.However, unfortunately, at the moment vaccination for cattle would be illegal under European law! The reason why EU legislation currently prohibits the use of bovine tuberculosis vaccines is because injectable vaccine for bovine tuberculosis in cattle interferes with the current tuberculin skin test and any vaccinated animal would show up as a reactor! However, the UK could seek a derogation from EU law, especially as exports are such a minute part of the cattle trade. It would also seem that the UK government is currently reluctant to approach the EU to discuss changes until they are satisfied that it satisfies the necessary criteria, whatever that may be! (question in the House of Lords). This is inexcusable after so much money has been spent and a vaccination programme should be made available without further delay and trials could commence now, perhaps using herds which are kept for reasons other than commercial.

The DEFRA report, 'Options for vaccinating cattle against bovine tuberculosis' (Ref.2), by the Veterinary Team bTB Programme, Food and Farming Group, June 2007 (last updated 12 July 2007), said that cattle vaccination has potential benefits to reduce prevalence, incidence and spread of bTB in the cattle population. It goes on to say that vaccination could help prevent breakdowns by preventing herds becoming infected by any source - wildlife or cattle, and could also reduce the severity of a herd breakdown. However, vaccination that is less than 100% effective will not guarantee all cattle are fully protected from infection and therefore vaccination alone cannot be used to define disease free status. BCG was suggested as the lead vaccine candidate in the short to medium term.

DEFRA has now revealed, in the latest consultation document, Bovine Tuberculosis: the Government's approach to tackling the disease and consultation on a badger control policy' (September 2010), that a vaccination for cattle will be available in 2012 (with the DIVA test). The BCG vaccine will not give 100% protection (estimates range from 50 -70%) and is not perfect - but then neither is the existing skin (or blood) test (estimates range from 70%). Vaccination could therefore be used as the basis for a successful control, rather than eradication, policy. It will be easier for farmers and cheaper in the long term too as cattle would no longer have to be slaughtered needlessly (with subsequent compensation costs) just because they are reactors or unconfirmed reactors to an unreliable skin or blood test.

However, the stumbling block is now the EU procedures, which, we are told, will not be completed until 2015! This is not good enough and derogation should be sought NOW so a vaccination programme can be started for cattle as a matter of urgency (already successful in trials in Ethiopia where they cannot afford to keep culling cattle needlessly). If cattle are vaccinated there may then be no need to tackle wildlife reservoirs, thereby saving these costs too. In these times of severe financial restraint and public cuts affecting so many people, the onus is on our politicians to choose affordable options. The Government has persistently failed to adequately justify the need for such an expensive, archaic and draconian bovine TB policy, either on the grounds of human or animal health or even on economic grounds.

The skin test poses real health and safety risks for farmers. In April 2010 an Irish farmer (from Moyne, North Longford), was injured whilst his cattle were being tested for bTB. He was pronounced dead when he reached hospital. About one third of fatalities on farms involve livestock. Change is needed - and now!

Ref. 1 BM Buddle, GW de Lisle, A Pfeffer and FE Aldwell, 1995 'Immunological responses and protection against Mycobacterium bovis in calves vaccinated with a low dose of BCG'.

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