What is CJD and spongiform encephalopathy?

A rare group of fatal diseases invade the brain through an agent known as a prion, causing dementia. The best known of this group is CJD, which has always been present in humans in low numbers but has been brought to public attention by the link with BSE.

Creutzfeldt-Jakob disease (CJD) is one of a small group of fatal diseases caused by an infectious agent which invades the brain and causes mental and physical collapse. The agent may exist in the body for many years before symptoms begin, but death may then result inside a year.

Different forms of the disease exist in humans and animals but all result in spongiform encephalopathy, so called because areas of the brain where cells have died appear like a sponge under a microscope. Diagnosis can only be confirmed after death by examining the brain.

There are about 50 confirmed cases of CJD a year in the UK. Some of the increase in the number of reported cases in the 1990s is due to more accurate diagnosis and raised awareness. However, there is a likely link between a new type of CJD and bovine spongiform encephalopathy (BSE) - 'mad cow disease'.

Other very rare spongiform encephalopathy diseases include:

• Gerstmann-Straussler-Scheinker disease (GSS) and fatal familial insomnia (FFS) can be inherited. There are fewer than five deaths a year in the UK.
• Kuru was common in the Fore tribe in Papua New Guinea. As part of a ritual women ate human brains and internal organs and many developed Kuru. Men ate the flesh and were at lower risk. Cannibalism stopped in the 1950s and disease has almost disappeared.

These diseases are called 'prion diseases' because the infectious agent is associated with an abnormal form of the protein PrP, known as a prion. The infectious agent, too small to see even under a powerful microscope, is extremely hardy and cannot be eradicated by normal sterilisation (although it can be very much reduced). It has even been found in ashes after incineration.

The prion takes a different form in each species but similar diseases are found in sheep (scrapie), cattle (BSE), deer, cats, mink and zoo animals. The infection has never passed from sheep to humans, but crossed to cattle from infected sheep protein in cattle feed and may now have passed to humans in beef products.

Since 1989, in the UK, action has been taken to remove from the food chain cattle brains and spinal cords, where greatest concentrations of infective agent are found. These and other measures suggest that the largest risk of transmission to people was during the 1980s. There is still controversy over whether enough has been done.

What are the symptoms?

CJD was first reported by two German doctors (Creutzfeldt and Jakob) in 1920, and usually attacks people over the age of 55. The prion may be present in the body for many years, passing to the brain through the nervous system. EEG tests may show changes in electrical activity in the brain. The cause of the prion being in the body is usually unknown.

• Early symptoms include minor lapses of memory, mood changes and loss of interest.
• Within weeks an infected person may complain of clumsiness and feeling muddled, become unsteady in walking, and exhibit slow or slurred speech. Eyesight often becomes blurred
• The disease progresses to jerky movements, shakiness, stiffness of limbs, incontinence and the loss of ability to move or speak. It is likely that the person is no longer aware of their surroundings or disabilities. Eventually the person will need full nursing care.
• People affected by CJD usually die within six months of early symptoms, often from pneumonia. In a minority of patients the disease may take two years to run its course. Very rarely the disease can last for many years.

There is no evidence that someone with CJD is in pain, provided they are well nursed and comfortable. Drugs can alleviate symptoms such as shakiness.

Can you catch CJD from an infected person?

There are no known cases of infection being passed to family members or health care professionals nursing an infected person and there is no need for precautions beyond normal good practice. Special precautions do need to be taken following a post-mortem.

Some people were infected by a corneal transplant, skin graft or growth hormone from an infected person. Surgeons also transmitted the disease through surgical instruments which had been used on the brain of an infected person. Today, no transplants are taken from infected people, growth hormone is made artificially and surgical instruments used on people with CJD are never used on other patients.

New variant CJD - the link with BSE

In 1996 a new variant of CJD was reported in ten younger people aged 19 to 41, with an average age of 29. In the early stages they became apathetic and nine of the ten were first referred for psychiatric treatment. Symptoms included muscle contractions an and loss of sensation. After death, signs of spongiform change and PrP were found in the brain.

In March 1996 the Government accepted that the most likely cause of the new variant was eating BSE-infected cattle.

The number of cases has remained small - 20 confirmed cases of the new variant in the UK as at September 1997. Some experts believe the number of cases will remain small. The most pessimistic predictions are for tens of thousands of cases a year.

Since the incubation period could be between ten and 30 years, there is not yet a firm scientific basis for predictions.

The Creutzfeldt-Jakob Disease Support Network has a helpline: 01630 673973

October 1997

Page Text supplied by The Alzheimer's Disease Society of Great Britain