Scientists at the research institute that produced "Dolly" the cloned sheep announced February 28, that they may have found a way to test for "mad cow"-like diseases in tissues outside the brain and spinal cord.
The finding may have a significant impact on the BSE drama. Although BSE was originally thought to be a problem only in the UK, recent cases of the disease in cattle in other nations has sparked a furor across Europe.
Researchers found that the expression of a certain gene was lower in the infected animals' tissues than in healthy animals. The investigators found that expression of a gene called erthyroid differentiation-related factor (EDRF) was reduced in the infected animals.
All the animal species that were tested can become infected with transmissible spongiform encephalopathies (TSEs). This class of fatal, neurologic diseases include BSE in cattle, a disease called scrapie in sheep, and variant Creutzfeldt-Jakob disease in humans.
Such diseases are notoriously difficult to detect, particularly before symptoms begin, and usually require testing of tissue from the brain or spinal cord.
These findings represent the first demonstration of a TSE-induced effect on gene expression outside the central nervous system. It is not clear what the normal EDRF levels are in humans, he said, and at what point during the disease process that EDRF production is affected.
While a test may help in screening cattle, he notes that an elimination of cow brains, spinal cord and other "risky" tissue from the human food chain should help halt the spread of TSEs to humans.
A test for humans may be the most important application.
It is not clear how many people may have been infected with variant Creutzfeldt-Jakob disease but are not yet showing symptoms.
These individuals, who are infected but not yet displaying signs of disease, may unknowingly transmit the agent to others through donated blood or improperly sterilized surgical instruments.
Nature Medicine March 2001;7:289-290, 361-364