By David N. Leff

What with mad cow disease frenzy busting out all over Europe, the French Atomic Energy authority has announced an overnight test to screen slaughtered cattle for the infection.

Its brief communiqui in the current issue of Nature, dated Jan. 25, 2001, bears the cryptic title: "Screening slaughtered cattle for BSE."

BSE stands for the prion infection's technical name - bovine spongiform encephalopathy. "In Great Britain, where the panzootic broke out in the mid-1980s, "observed prion disease specialist Jean-Phillipe Deslys, "there have been 180,000 cases of BSE," and vast herds of British cattle have been killed preemptively.

Deslys, who directs prion research at France's Commissariat ` l'Energie Atomique (CEA) in Fontenay-aux-Roses, near Paris, said "there are 88 human cases of new-variant Creutzfelt-Jakob Disease [CJD] in Britain, and three in France, two of whom have already died of the infection." Strong circumstantial evidence links CJD to consumption of beef-derived products from infected cows fed on recycled animal offal from other infected animals.

"The human cases of CJD we have observed in France," Deslys told BioWorld Today, "are certainly linked to British bovine meat products. The contamination supposedly began at least 10 years ago. This means, unfortunately, that our importation of British cattle represented 5 percent to 10 percent of French consumption - until our embargo in 1996. It has also been exported to many European countries, but not France, since we banned offal cattle feed."

On Jan. 1, the European Union published a package of measures to combat BSE, and protect human health. It validated the rapid test developed by CEA, which detected pathogenic samples in all brain materials proved infectious to mice. It compared the results of this test to a conventional mouse bioassay method on which most consumer protection measures are based.

Mouse Test Results Took Year Or Two

"Laboratory mice infected with infectious prion particles from first-passaged ruminants," Deslys recounted, "develop clinical symptoms between one and two years after inoculation, depending on the infectious doses. First, they stop grooming their fur to keep it clean, then begin to stagger with ataxia. Next come problems of locomotion, paralysis and at the end, death." These animals, he said, "are good for fundamental research only. You can't use them for routine testing - blocking your cow carcass for two years. It's not a slaughterhouse test.

"The EU's just-published measures," Deslys pointed out, "exclude from human food consumption all bovines over 30 months old, if they have not been tested. Meaning that you have the choice of going to the slaughterhouse and having the test, or destroying the cow. Some countries are putting in more drastic criteria," he added. "Germany has changed the level from 30 months to 24.

"Now, at the slaughterhouse," Deslys recounted, "you sample the brain stem of the cow carcass. Meaning that you take a piece of brain that is readily accessible. Then the samples are sent to a local lab that is going to perform the systemic analysis. This takes less than five hours, after which the carcass - if negative - can be released for human consumption.

"The important thing to know," Deslys went on, "is that at the slaughterhouse there is a special phase - lowering the temperature of the carcass. Which means after killing the animal and cutting it into two big pieces, they leave it in the fridge for the night, until the carcass is at 7 degrees centigrade. It's important. If not, the meat is not of good quality. So you have this time interval in which to perform the rapid test and get the results.

"This slaughterhouse test with its five-hour timing is only to release animal carcasses with a clean bill of health, not to screen live herds. For the moment," he pointed out, "it is not possible to do our test on a living cow. It is possible in sheep, because you detect the appearance of their scrapie in peripheral tissue, but not in bovines.

"Our test has been developed to guarantee that the food chain would not be dangerous for man. During the first study we had only an intercomparison of more or less sensitive tests. But the question was: 'Okay, that's true. Your test is 30 to 10 times more sensitive than the others. But what guarantee does it give to the consumer? We understand that you are able to detect the disease to more efficiently eliminate animals. But what does it mean for the animals you find negative?' That," Deslys observed, "is all the purpose of our demonstration, and of this Nature paper."

"It's not our purpose to commercialize anything," he pointed out, "so our institute has tried to find an industrial partner to handle CEA's rapid BSE test for us. And we found a French company at the beginning, the Pasteur Diagnostique, which has since been bought by Bio-Rad, headquartered in California.

Prion Disease Infects Elk In Western States

He made the point, "In Europe, there is no concern regarding scrapie in sheep. Germany intends to begin a large-scale systemic test of prion infection in sheep. This tool could also be used for more extended epizootic diseases as an approach to protect against prion diseases in the U.S. - such as scrapie in sheep and chronic wasting disease in wild ruminants, such as elk and mule deer in the Western states." Deslys observed that "10 percent of such animals killed by hunters are positive for the disease.

"From a philosophical point of view," Deslys ruminated, "this European BSE crisis demonstrates that before you had antagonism between economic constraints and public health. And that's why there is a crisis. Because people think that they can't trust anything anymore."

Now you see that the scientific and biotechnology approach, which was said by many people a few months ago to be impossible, will turn out very quickly to solve the problem - meaning that if you are able with a sensitive test to guarantee the security of the consumer, then you have no more reason to have a crisis, and no more reason to slaughter millions of cows.

"So," he concluded, "You avoid wasting millions and millions of dollars. And that's very motivating for research teams."