Is eating meat infected with bovine TB harmful?
“Tens of thousands of diseased cattle, slaughtered after testing positive for bovine tuberculosis (bTB), are being sold for human consumption by Defra, the food and farming ministry,” reports The Sunday Times.
Following an investigation, the paper says it found that the meat is being sold to caterers and food processors by the government’s food and agriculture department, despite being banned by most supermarkets and burger chains.
It is important to note that your risk of catching TB from eating meat from an infected animal is minimal.
What is bovine TB?
Bovine tuberculosis (bTB) is an infectious disease in cattle which primarily affects the lungs. It is thought to be transmitted within herds by inhalation of infected aerosol droplets from infected cattle.
Bovine TB can affect a range of wild and domesticated mammals, including cattle, deer, pigs, and badgers. The government is planning ‘pilot’ badger culls in two areas this year to see if these will reduce bTB in cattle by limiting the spread of bTB from badgers to livestock.
Bovine TB is caused by Mycobacterium bovis bacterium, which is closely related to the bacterium that is the most common cause of TB in people (Mycobacterium tuberculosis). Like human TB, bTB primarily affects the airways and lungs.
The bTB bacteria can also infect humans and cause tuberculosis, although this is reported to be mainly through people consuming unpasteurised milk or dairy products (pasteurisation kills the Mycobacterium bovis bacteria).
Infection can also occur in people who come into close enough contact with infected animals by inhaling the bacteria-containing aerosol droplets exhaled by them – but this is thought to be rare. Humans can also be infected via direct contact with a wound, such as what might occur during slaughter.
However, transmission to humans is reported to be uncommon in the developed world. The UK’s Health Protection Agency (HPA) suggests that in the 17 years from 1994 to 2011 there were 570 reported human cases of Mycobacterium bovis infection (about 33 a year). Most of these were in people aged 45 or over, and could have been infected before milk pasteurisation and meat inspection became common in the UK.
bTB in humans is reportedly more common in the developing world. This is due to people consuming unpasteurised milk in areas where TB is not controlled, and people living closely with their livestock. A 2006 study estimated that there are 7,000 cases of bTB a year in Latin America.
What are the symptoms of bovine TB in humans?
Not everyone exposed to the Mycobacterium bovis bacterium will develop symptoms. If symptoms of bovine TB occur, they can include:
- fever
- night sweats
- persistent cough
- diarrhoea
- weight loss
- abdominal pain
As with human TB, people who have caught bTB will be given a combination of antibiotics to kill the Mycobacterium bovis bacteria.
What do the authorities say?
DEFRA states that The Sunday Times’ claim that people are at risk of contracting bovine TB through eating meat is “irresponsible scaremongering”. It says that the Food Standards Agency has confirmed that there are no known cases of people contracting TB from eating meat.
DEFRA says that all meat from cattle killed due to being infected with bovine TB must have rigorous food safety checks before it is passed as fit for consumption. Therefore, it says that any risk is extremely low, regardless of whether or how the meat is cooked.
The department also notes that the risks have been reviewed by the Food Standards Agency’s independent advisory expert panel (the Advisory Committee on the Microbiological Safety of Food) in 2002 and 2010, and by also the European Food Safety Authority.
What is done to control bovine TB currently?
DEFRA states that the risk to human health from bovine TB is very low these days, mainly due to milk pasteurisation and the early identification of cattle with TB on farms and at abattoirs.
It is running a programme which aims to reduce and ultimately eradicate bovine TB, called the Bovine TB Eradication Programme for England. One part of this is the ongoing testing of herds for bovine TB. This involves a tuberculin skin test.
Cattle in herds and areas where disease risk is highest are tested annually, and in all other areas they are tested every four years. Cows aged 42 days old or older that are being transported also need to have tested negative for TB no more than 60 days before being moved. Cows found to be infected with TB are killed in an attempt to halt the spread of the disease.
