The basics of mad cow disease
What is mad cow disease?
Mad cow disease is the common name given to bovine spongiform encephalopathy or BSE.
BSE only affects cattle, but there is a human form of the disease called variant Creutzfeldt-Jakob disease or vCJD.
vCJD is believed to be caused by eating beef products contaminated with central nervous system tissue, such as brain and spinal cord, from cattle infected with mad cow disease. For this reason, there are strict controls in place with regards to cattle, to prevent BSE entering the human food chain and safeguard the public from vCJD. In the UK these controls include requirements that all materials from animal carcasses that could be infected with BSE are destroyed, routine testing of all cattle over 30 months old, a ban on feeding farm animals on meat and bone meal and a ban on mechanically recovered meat.
Cases of vCJD are rare, with 177 recorded cases of variant CJD in the UK since the condition was discovered.
What are the symptoms of vCJD?
The disease can affect all age groups and is very hard to diagnose until it has nearly run its course. In the early stages of vCJD people have symptoms related to the nervous system, like depression and loss of coordination. Later in the illness, dementia develops. But only in advanced stages of the disease can brain abnormalities be detected by MRI (magnetic resonance imaging). vCJD is fatal, usually within 13 months of the onset of symptoms.
Is it possible to get vCJD from eating food purchased in the UK?
It is extremely unlikely that this would happen. The strict controls in place since 1996, the testing and prohibiting of high-risk animals from entering the food supply, as well as the removal of high risk materials from the food supply, helps provide reassurances that BSE is not a risk to consumers.
Can you get vCJD from drinking milk from an infected cow?
Milk and milk products are not believed to pose any risk for transmitting mad cow disease to humans. Experiments have shown that milk from mad cow-infected cows has not caused infections.
Does cooking food kill the prion that causes mad cow disease?
Common methods to eliminate disease-causing organisms in food, like heat, do not affect prions. Also, prions only seem to live in nervous system tissue.
What other types of CJD are there?
Sporadic CJD is caused by faulty genes. It is the most common type of CJD, although it is still very rare.
Familial CJD is a very rare form of CJD caused by an inherited gene mutation or abnormality. Symptoms of familial CJD are not usually seen until someone is in their 50s.
Iatrogenic CJD occurs when the CJD infection is spread from someone with CJD through medical or surgical treatment. Most cases of this form of CJD were due to children of restricted growth being given human growth hormone treatment.
Is CJD contagious?
CJD can be transmitted from an affected person to others through an injection or eating infected brain or nervous tissue. Variant CJD has been transmitted on four occasions in the UK by blood transfusions.
There is no evidence that sporadic CJD can be caught from everyday contact with people who have the condition or by airborne droplets, blood or sexual contact.