ACROSS Edinburgh, teams of scientists are searching for answers to one of the most deadly and frightening diseases to hit the UK in recent years - variant Creutzfeldt-Jakob disease (vCJD).
The National CJD Surveillance Unit at Edinburgh University is not only counting cases of the disease, thought to be caused by having eaten Bovine Spongiform Encephalopathy (BSE)-contaminated meat, but is also looking for clues as to how it can be sto
pped. Now experts from around the world are meeting in Edinburgh at Prion2007 to discuss vCJD and related diseases, and how they might be tackled.
Professor James Ironside, a professor of clinical neuropathology at the Edinburgh unit, is one of those investigating prion diseases - those caused by abnormal proteins in the brain. He says that after the crisis of "mad cow disease" and subsequent vCJD infections in humans, the UK had a "special relationship" with such diseases.
Ironside says this means we should remain wary of new threats to humans from animals, including from scrapie - a prion disease mainly affecting sheep.
"There's a feeling in many areas that BSE is over and it's extinct," says Ironside. "It's not quite extinct in the UK, but there is a feeling we don't need to bother about these things any more. But, as with any other diseases, the more you look, the more you find, and recently there have been new forms of BSE and new forms of scrapie identified in animals in the UK and Europe. They have found a form of atypical scrapie. It actually turns out to be probably more widely distributed than the typical form of scrapie.
"The idea that this problem is over is not completely true. There are still unresolved questions that we need to find out about."
Ironside says a lot of time and effort has been put into scrapie in sheep, and trying to reduce its incidence, and that these efforts have worked. But, he adds: "That was all set in place before these atypical forms were identified, so in a way it's a completely different disease and we have to bear that in mind without being scaremongering."
Ironside says there is still debate about whether BSE came as the spontaneous result of cows eating feed made from animal remains, or if it originated from a type of scrapie. He says that while there is no evidence of it so far, atypical scrapie has the potential to be transmissible to humans and this prospect is currently being studied.
"You can study its transmission characteristics in mice," Ironside says. "We will have to see how these diseases go. One problem with these diseases is that although we do have models of infection, the incubation periods tend to be lengthy. Even in mice, incubation periods can be a year or two years and that is not uncommon."
Ironside says he is still stunned that cattle were fed the remains of other animals, thus allowing BSE to pass to humans in the form of vCJD. And he adds there are still good reasons to keep BSE prevention measures high to stop another widespread outbreak.
"I don't want to be alarmist about this, but with the relaxation of measures for BSE, and this occurring Europe-wide, what we don't want to happen is another outbreak of BSE or some other form of these diseases in Britain or anywhere else," he says. "We need to make sure that the steps that halted the infection of cattle with BSE continue. It basically boiled down to a form of cannibalism, feeding animal remains to animals. I had no idea that was going on, and I think most people didn't. It just seems wrong.
"Also, the contaminated animal feed from the UK was exported to other countries, so BSE has popped up not just in Europe but in Japan and places like that. We know the animal feed also went to other countries that don't have the resources to test for BSE, in Asia for example.
"What I wouldn't like to see is BSE from these other countries somehow, with globalisation, causing a boomerang effect so it comes back."
The threat from the previous outbreak is also far from over. While cases of vCJD are declining, Ironside and others have raised fears that many people may be harbouring the infection without developing symptoms.
This means they might pass it on through blood donations or on contaminated surgical equipment. Long incubation periods for the disease may mean that due to genetic influences, some people may not develop vCJD symptoms for many years to come. It is hoped that a rapid screening test could help prevent the disease becoming endemic through blood transfusions and surgery. But there are also ethical concerns over what you tell someone who is found to be infected but might never develop clinical disease, with no cure or treatment currently available.
Ironside says this made the search for vaccines and treatments all the more important, but this held challenges.
"The problem with treating any type of brain disease is a thing called the blood-brain barrier, which stops certain types of drugs, including some really useful drugs, from getting into the brain," he says. "That is why some of these drugs have to be injected through the spinal cord.
"There are some studies of compounds in animals and cell cultures which have been shown to slow down the progression of these diseases. A lot only seem effective if given before or in the early stages of disease. I'm more optimistic about treatments, but I don't think it's going to be a quick win."
• Prion2007 begins tomorrow at the Edinburgh International Conference Centre.
