London

Ian Wilmut, who led the team that created Dolly the sheep, has called for better assessments of the health of cloned animals, after revealing that Dolly has developed arthritis.

Wilmut, of the Roslin Institute near Edinburgh, says that Dolly's condition could have arisen because of genetic defects caused by the cloning process.

“What makes people slightly concerned is that Dolly has developed the arthritis in her hip and knee joint,” Wilmut says. It is not uncommon for a five-year-old sheep to develop arthritis, but it usually strikes the elbows. Dolly is receiving anti-inflammatory drugs but may have to be destroyed if her condition deteriorates.

Wilmut says that other groups developing cloned animals could have failed to reveal similar abnormalities. “I'm not sure that other companies are actually monitoring or publishing this information,” he says. Wilmut suggests that independent assessment of cloned animal health and anonymous publication of the findings is needed before the technology is used on a large scale.

But other researchers insist that such information is already recorded and published. “I'm surprised, because I thought we had all been rather open,” says Robert Lanza, a senior scientist at Advanced Cell Technology, based in Worcester, Massachusetts, a company that is also developing cloned animals. “We have just published a very comprehensive study where we analysed in extensive detail virtually all of our cloned animals fully from birth to adulthood,” he says.