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New BSE test could calm fears over beef safety

By Ahmed ElAmin , 31-Aug-2005

A new test designed to quickly detect mad cow disease in live animals may help calm the public's fears about the safety of their beef.

At the moment there is no test to screen animals for Bovine spongiform encephalopathy (BSE) before they enter the food chain. Current tests only work by sampling the brain tissues of the dead host.A test for live animals would vastly reduce the chance of them entering the food chain.

European consumers have been concerned about the safety of beef and beef products ever since the BSE scare hit the headlines in 1996. In the EU poultry consumption overtook demand for beef and vealin 1996.

 

Since then the EU has implemented strict feeding, tracking and testing programmes for cattle. The UK's beef industry was hit hard by the outbreak as the European Commission placed toughrestrictions on its exports.

 

Before the BSE crisis in 1986, the UK's beef exports were worth about £1bn (€1.5bn) compared to £20m (€29m) last year, according to Food from Britain, a consultancy.

 

BSE, as mad-cow disease is called, and the human form of the disease, variant Creutzfeldt-Jakob disease (vCJD), are caused by a rogue version of a prion protein, PrPSc. The disease eventually killsthe host.

 

Now neuroscientist Claudio Soto from the University of Texas says he has developed a way in reliably detecting the malformed proteins that cause vCJD in blood samples taken from hamsters. Theirtest takes only a few days to complete and can be performed on the live animal.

 

He says the procedure could be used for testing humans and animals. It could be used to check stocks in blood banks, where there is currently no screening process. Two of the people who died ofvCJD in Britain are believed to have contracted the disease through transfusions.

 

vCJD is a rare disease that only needs a few prions to infect the brain. The misshapen proteins apparently multiply by changing the conformation of normal proteins that they come into contact with,eventually leading to a fatal neurodegenerative illness.

 

Since the prions concentrate in the brain, scientists have found it a huge challenge to detect the few that circulate in the blood. Using current testing procedures scientists must first obtainbrain tissue from a dead animal to find out whether it is infected with the disease.

 

To get around the problem some scientists have tried extracting blood from live subjects and injecting this into another animal's brain. They then wait, typically for months, to see whether theanimal receiving the shot develops the clinical traits of the disease.

 

But this method has a high failure rate. It only succeeds in picking up on an infection 31 per cent of the time it is present, Soto and his co-researchers stated in an article published this monthin Nature Medicine magazine.

 

Soto's method allows testers to take a sample of blood from a live animal and then amplify the negligible levels of the misshapen proteins in blood to a detectable level.

 

His technique involves mixing normal proteins with tiny amounts of the infectious version in a test tube, causing the abnormal molecules to multiply and clump together over a period of about halfan hour. A pulse of sound break up the clumps, allowing the misshapen proteins to repeat the process until they reach detectable levels.

 

Tests on 18 diseased and 12 healthy hamsters revealed that this method could detect prions 50 per cent of the time they were present after two 140-cycle runs. After six runs the success rate wasboosted to 89 per cent. The test did not give any false positives, the researchers reported.

 

Soto said he can adapt the technique to run tests on human blood within six months. But Soto stated the procedure will need much more testing, and adds that there are ethical issues about screeningfor a disease that has no known cure.

 

"That's an important question that someone has to resolve," Soto stated in the magazine.

 

A total of 181 people have died from vCJD or are suspected to have the disease and are still alive, according to a toll compiled by AFP from official figures.

 

The UK has 157 confirmed or suspected cases, followed by France (14), Ireland (three) and single cases reported in Canada, Italy, Japan, the Netherlands, Portugal, Spain and the US.

 

The UK was the epicentre of the BSE outbreak in the late 1986. At its peak in 1992, a total of 37,280 cases were discovered in UK cattle.

 

Scientists suspect the source was cattle feed that came from cows with the brain disease. The disease then leapt the species barrier to humans through the consumption of contaminated beef,according to the evidence.

 

The number of BSE cases found this year in European countries is falling dramatically, except for Spain.

 

So far this year the UK remains at the top of the BSE list, with 66 cases confirmed, indicating that the total for the year could fall by about 60 per cent. Spain has reported 52 cases so farthis year, Ireland 37 cases and Portugal 13 cases. Germany and France have so far not reported any incidents of BSE.

 

Poland reported 11 cases of BSE last year and has so far discovered another 11 cases this year.

 

According to the World Organisation for Animal Health, Ireland found 126 cases of BSE in its cattle last year, compared with 137 found in Spain.

 

The UK had the highest incidence of BSE cases in the world last year with 343 cases confirmed, followed by Spain, Ireland. Portugal is fourth in the BSE league, reporting 92 cases in 2004, followedby Germany with 65 cases. France reported 54 cases of BSE last year.

 

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