The announcement last year of the cloning of Dolly the lamb led to an international response unprecedented in medical ethics. Within hours, Presidents Clinton, Chirac and Santer had called on their ethics committees for advice on the implications for humans, while international agreements on bioethics that had been all but finalized by the Council of Europe and Unesco were quickly modified to include a ban on human cloning for reproductive purposes.

“The wrong issue for a moral panic,” sighed at the time David Shapiro, then executive director of Britain's Nuffield Council on Bioethics, arguing that if there was an area of medical ethics in dire need of international regulation it was not cloning but xenotransplantation. For, however hard countries such as the United States or United Kingdom attempt to regulate xenotransplantation to reduce the risk of creating human diseases, their efforts will be in vain if other countries adopt weaker or no regulations. Such countries could become ‘xeno-havens’ for unscrupulous surgeons, allowing animal viruses to escape into the human population (Nature 385, 378; 1997).

“The prospect scares the hell out of me,” says Daniel Salomon, a scientist at Scripps Research Institute in California, and member of the board of the American Society of Transplant Physicians, a body that has long waged war on the trafficking of human organs in developing countries. The exorbitant costs of meeting the stringent regulatory requirements for clinical xenotransplantation now being developed in the United States and other industrialized countries will create a strong incentive for traffic in xenotransplants with ‘xeno-havens’ providing cheaper alternatives, argues Salomon. The big risk, he says, is that humans will end up with virus-laden organs from baboons and chimpanzees, rather than from specially bred pigs which — even given the acknowledged dangers — should nevertheless be safer.

The European Commission has yet to take a position on clinical applications of xenotransplantation. Ironically, one reason is that the agenda of the scientific steering committee that advises the commission on technical issues is currently jammed with issues arising from the aftermath of the bovine spongiform encephalopathy crisis, according to Paul Vossen, a commission spokesman.

One official from the World Health Organization (WHO) admits that the growth of interest in xenotransplantation has caught the organization off guard. It has since moved speedily, setting up a xenotransplantation advisory committee last autumn, and planning to release guidelines on the technology within the next few months.

But many argue that WHO guidelines are not enough, pointing out that WHO is not a regulatory authority, so any regulation of xenotransplantation technology at the national or international level will be up to national governments. “We need some kind of formal binding international agreement,” says Salomon.