Mad cow disease: why you shouldn't panic

If you're under 30 the last time mad cow disease hit the UK, you were either a wee bairn or not even born yet.

On Thursday a new case was reported to have been found in a dead cow in Wales, but authorities have said there is no threat to public health and the disease has not entered the food chain.

If you were wondering what all the fuss was about, though, let us bring you up to speed:

What is it?

Bovine spongiform encephalopathy (BSE), or mad cow disease, is a fatal neurodegenerative disease in cows that affects the brain and spinal cord by basically turning them into jelly (it's not a good way to go).

It has a long incubation period, of between two and a half to eight years. All cows can get it and the symptoms of aggression, adverse reactions to noise and touch, lethargy and decreased appetite usually manifest when the cow is around four-five years of age.

How do cows get it?

There's no known origin of the disease, but cows get it when they are fed cow meat. Fairly obviously this usually happens as a result of human error: in the UK outbreak of the 1990s, an investigation concluded that cattle were fed infected meat and bone meal, which spread the disease rapidly.

How do humans get it?

The infectious agent in BSE is a type of protein called a prion, which is not destroyed even if meat is cooked. In humans, the disease takes a form called variant Creutzfeldt-Jakob disease (vCJ), which affects the brain.

The disease is hard to diagnose until its final stages: early symptoms include depression and lack of co-ordination, and then dementia. The disease is usually fatal between 6-12 months of contraction.

By June 2014, vCJ had killed 177 people in the UK and 52 more people worldwide.

What happened in the UK in the 1980s and 1990s?

Mad cow disease was first discovered in the UK in 1986 and at the peak of the crisis in 1993, almost 1,000 new cases of BSE a week were identified.

The impact on the farming community was huge and it is thought 4.4 million animals were slaughtered during the efforts to eradicate it.

The crisis led the EU to ban exports of British beef in 1996, a restriction that was kept in place for ten years and caused much ill will between the UK and its trade neighbours.

Safeguards mean the disease is largely under control now - only one case in the UK before now has been reported since 2012.

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