Jonathan Leake at the Sunday Times tells us that tens of thousands of cattle (Bos primigenius), slaughtered after testing positive for bovine tuberculosis (bTB), are being sold for human consumption in Britain. Mr Leake says this is being done by the Department for Environment Food and Rural Affairs (DEFRA).
DEFRA says that Mr Leake’s story is ‘irresponsible scaremongering’. DEFRA says that the Food Standards Agency (FSA) ‘has confirmed there are no known cases where someone has contracted TB from eating meat. All meat from cattle slaughtered due to bovine TB must undergo rigorous food safety checks before the meat is passed as fit for consumption. As a result, the risk is extremely low, regardless of whether or how the meat is cooked.’
Do we trust DEFRA and the FSA on this? I’m inclined to trust. But our beef, meat processing and retail industries suffered ‘Horsegate’ only a few months ago. Some people don’t trust products labelled ‘beef’ now.
Here’s a new reason for doubt, perhaps. If you buy beef in Britain, do you want to know whether the animal had bTB? After all, animals can be certified fit for human consumption if they’ve had trivial diseases. Is bTB trivial? No, it’s not trivial for the animal or for the farmer. It might not be trivial for the consumer, either.
In people, tuberculosis (TB) is usually caused by a bacterium called Mycobacterium tuberculosis. But we can get ill also from a closely related bacterium, Mycobacterium bovis. That’s bTB. In other words, bTB is zoonotic. It can infect both animals and people.
Here’s some science. In 2005 Ricardo de la Rua-Domenech at DEFRA presented a peer-reviewed (that means, we hope, unbiased) review of evidence about the UK incidence, risks, control measures and zoonotic aspects of bTB.
Dr de la Rua-Domenech says, ‘Human infection with M. bovis in the UK has been largely controlled through pasteurization of cows’ milk and systematic culling of cattle reacting to compulsory tuberculin tests… Most cases of zoonotic TB diagnosed in the UK are attributed to (i) reactivation of long-standing latent infections acquired before widespread adoption of milk pasteurization, or (ii) M. bovis infections contracted abroad.’
He concludes, ‘Given the increasing numbers of cattle herds being affected each year, physicians and other public health professionals must remember that zoonotic TB is not just a disease of the past. A significant risk of M. bovis infection remains in certain segments of the UK population in the form of (i) continuing on-farm consumption of unpasteurized cows’ milk, (ii) retail sales by approved establishments of unpasteurized milk and dairy products and (iii) occupational exposure to infectious aerosols from tuberculous animals and their carcases.’
All right, we’ve got the message about pasteurisation. Is there a risk from meat too? Perhaps not, unless you chew on a TB-raddled lung. Which you’re not going to do. Are you? Even if you wanted to do that, it wouldn’t make it past the meat inspectors. Carcase parts with TB lesions aren’t allowed onto butchers’ shelves.
But here’s the rub. If the lesions are only in a few parts of the carcase, those parts are cut off and the rest can be sold as food.
The Health Protection Agency (HPA, part of Public Health England) says that meat inspections are good enough to protect us from bTB. ‘Meat is highly unlikely to be a source of infection in Great Britain, as the routine TB testing programme means that cattle with TB are generally identified at an early stage of infection and cases of advanced disease with TB lesions in the muscle and bone tissue are very rare. Furthermore, carcasses containing signs of TB are completely or part condemned during meat inspection in the abattoir. Any TB bacteria that might still be present in or on the meat would be killed by normal cooking.’
Due to the concerns about bTB in beef, meat from animals which have tested positive has been banned from several supermarkets. But it’s still being served in schools, hospitals and the military.
You can see more under my ‘tuberculosis’ tag. If the concern about TB-infected cattle turns into a food scare, I’ll tell you what news I find.