New Concern of Humans Catching "Mad Cow" Disease

After a 10 percent loss in sales on the world market, the European industry suffered another blow at the end of March, with the appearance of the first case of bovine spongiform encephalopathy -- mad cow disease -- in the Netherlands.

Nonetheless, some 50 researchers from 15 countries meeting the last week in March concluded that it was not yet possible to establish a clear link between mad cow disease and new forms of CJD, although "recent findings strengthen that hypothesis."

But Paul Brown, with the National Institutes of Health in Bethesda, Maryland, said epidemiological studies have demonstrated that the probability of contagion for the average person was "zero."

Nevertheless, last week's scientific conference, convened by the World Health Organization (WHO), underlined the need for continuous, intensified research.

It recognized that the lack of an early diagnosis tool was a major obstacle. CJD is diagnosed by injecting lab animals with samples of infected brain tissue.

The conference suggested the WHO draw up recommendations on the disease for its 191 member states. The guidelines should include avoiding the use of raw beef by-products in the preparation of medicine. In cases in which the use of such materials is essential, it must come from countries certified as being free of mad cow disease.

In the light of experiments carried out by Brown in Bethesda, the scientists also recommended monitoring blood transfusions to prevent CJD carriers from donating blood. While it has not yet been demonstrated that the disease can be transmitted from one person to another through transfusions, Brown told a press conference he had found that traces of CJD could remain in processed plasma.

David Heymann, director of the WHO Division of Emerging and other Transmittable Diseases, concurred that there was no proof that CJD could be transmitted by blood transfusion. Nevertheless, he added that as a precautionary measure, the blood of people with CJD and other transmittable spongiform encephalopathies should not be used.

Some people were infected with CJD in the 1980s through the use of human growth hormones. Pituitary glands from corpses began to be used as a source of growth hormones in the 1960s, but that practice was discontinued in 1985. Due to the long incubation period of CJD, such cases are still turning up in the United States, France and Great Britain.

The recommendations by the scientists also extend to those patients who received grafts of a certain brain membrane used in surgery, which is also obtained from corpses, and in the past was extracted in some cases from people who had died of CJD, said Brown.

The three groups -- CJD sufferers, those who took natural growth hormones and people who received grafts of the brain membrane in question -- along with those who have a hereditary disposition to CJD should be excluded from donating blood, organs and other tissues, the conference underlined.