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Can bovine TB spread to humans?

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The simple answer is 'yes', but it is not very likely. Currently less than 1% of cases of TB in humans are caused by bTB and a significant proportion of these are in humans over 70 years old (reactivation of ancient infections) or immigrants from developing countries. With modern living conditions, better sanitation and the widespread use of pasteurisation/cooking, the risk is extremely low. The Health Protection Agency has confirmed that the risk to humans is negligible (so small or unimportant as to be not worth considering). It is interesting to note that around 60% of the human population are in areas where bovine TB is either only partially controlled or not controlled at all (ref 1).

There are three ways humans can get bovine tuberculosis:
    * by breathing or inhaling air contaminated with the bacteria after an infected animal or infected person coughs or sneezes very close by. However, cattle owners and TB testers on farms take no precautions when in contact with cattle, wear no masks and do not contract the disease. They do, however, suffer physical injuries because of the high health and safety risks involved with cattle handling
    * by drinking unpasteurised milk from an infected cow or eating raw or undercooked meat from an infected animal.
    * by handling infected meat in the dressing and processing of animal carcasses, especially if hands aren't washed carefully prior to consuming food. There is very little risk that an individual would contract bovine tuberculosis by this method borne out by the fact that even abattoir workers and vets very rarely contract the disease.

Some websites choose to publish unsubstantiated animal to human transmission figures but they provide no evidence to substantiate their claims. In fact it is extremely rare to contract bovine TB from contact with farm animals or products from farm animals.

The Food Standards Agency confirm meat is safe; 'Where a carcass shows evidence of localised TB, the lesions are cut out and the rest of the carcass is passed as fit for human consumption.' In fact the carcasses are even sold back into the food chain by DEFRA in an attempt to recover some of their costs.

An FSA spokesman said 'there had not been a single documented case of someone developing human TB after eating infected meat'.

TB is no longer the human health problem it once was, particularly now virtually all milk is pasteurised and meat is cooked (pasteurisation and cooking kills off any TB bacteria). This is a fact that is very rarely mentioned in any public debate, government report or official paper on the subject. Bovine TB may be a 'zoonosis' (ref 2), but figures reveal that, despite the alleged increase in bovine TB in cattle and other animals in some areas of the UK, still under 1% of all confirmed cases of TB in humans is due to M. bovine (the human form), so the spread to humans is extremely rare (refs. 2 & 3). Even the Health Protection Agency says the risks from bovine TB are ‚'negligible', (ref. 4). The dictionary definition of ‚'negligible'‚ is ‚"so small, trifling, unimportant that it may safely be neglected or disregarded‚". If this is the case then should we be asking whether the whole TB issue is being blown up out of all proportion?

In the paper (Ref. 5) by the Professors Paul and David Torgerson, 'Public health and bovine tuberculosis: what’s all the fuss about?' it states that: 'In the UK, cattle-to-human transmission is negligible. 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.' It goes on to say that; 'Before milk pasteurisation, M. bovis was isolated from 8% of churn samples and almost all 3000-gallon tankers suggesting widespread exposure to bTB. Even then most did not get the diease. Since milk pasteurisation was generally introduced in the UK in the early 1960s, bTB has declined drastically.'

‘Public Health and bovine tuberculosis – what’s all the fuss about?’ is a very well researched and referenced article, which concludes that bTB control in cattle is irrelevant as a public health policy and there is little evidence either for a positive cost benefit in terms of animal health of bTB control. It suggests that such evidence is required; otherwise there is little justification for the large sums of money spent on bTB control in the UK. It states that in reality cattle-to-human transmission is negligible. 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. It goes on to say that there is little evidence for a positive cost benefit in terms animal health of bTB control.

As mentioned earlier, the government is so confident that bovine TB is not a health problem regarding meat for human consumption that carcasses from certain slaughtered reactors and inconclusive reactors are sold back into the food chain once any visual lesions have been removed. Interestingly many cattle slaughtered as bTB reactors show no signs of disease during life, at slaughter or following tissue culture. The govrenment advises this is not because they do not have bTB but the lesions are probably too small to pick up, so meat for human consumption could include lesions. However, cooking should destroy any bacteria. It is interesting to note that plenty of meat is also imported into the UK from countries where TB is endemic.

The current UK bovine TB policy and associated media hype is causing unnecessary concern and confusion among the public. It is having a detrimental effect on the farming industry, costing the taxpayer millions and causing severe problems for many farmers and cattle owners.Testing of cattle carries more human health risk from injury than the disease it is testing for. There are also animal welfare issues involved.

Is the existing policy therefore archaic and flawed? Is it time for a very radical re-think and change of direction? We believe it is.

Ref. 1. O Cosivi, JMGrange, CJ Duborn, MC Raviglione, T Fujikura, D Cousins, RA Robinson, HF Huchzermeyer, I de Kantor, FK Meslin, 1998 'Zoonotic tuberculosis due to Mycobacterium bovis in developing countries'.

Ref. 2. Zoonoses Monitoring

Ref. 3. In 2007, there were 279 cases of confirmed TB in the South West region and of those two were confirmed as the bovine strain. The current risk posed by bovine TB to human health in the UK is considered negligible. Bovine TB, like any other strain of TB, is treatable with a six-month course of antibiotics which must be completed in order for the treatment to be effective.

Ref. 4. Health Protection Agency

Ref. 5 ‘Public Health and bovine tuberculosis – what’s all the fuss about?’, by Paul R Torgerson and David J Torgenson can be read at http://www.zora.uzh.ch/47412/

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