People who have animal organs transplanted into them overseas might be monitored for the rest of their lives if they come to New Zealand, under proposals published today.

A discussion document from the Bioethics Council says New Zealanders and foreign tourists with animal organs, most likely pig hearts or kidneys, will need to be regulated even if transplanting animal organs into humans, or "xenotransplantation", is banned in New Zealand itself.

Such "xenotourists" may be asked to disclose their transplants when they arrive, go on a national register, give blood samples for regular health checks, have their relatives informed and their travel restricted and, in extreme cases, be quarantined.

"Many of these measures would involve a severe infringement of an individual's right to confidentiality, to refuse medical treatment and to freedom of movement," the council says.

Its 43-page discussion document kicks off a national debate leading up to June this year, when a law imposing strict controls on xenotransplantation expires.

The law was passed three years ago after Auckland company Diatranz sought to transplant cells from the pancreas of pigs into human diabetics to make extra insulin in their bodies, removing the need for daily insulin injections.

Diatranz has since changed its name to Living Cell Technologies and moved its head office to Australia.

It has just finished trials on monkeys in Singapore and plans human trials in the United States this year. But it continues to extract the pig cells in Auckland.

Auckland surgeon Stephen Munn, who transplanted a kidney from radio host Grant Kereama into former All Black Jonah Lomu last year, says New Zealand should be ready to transplant pig hearts and kidneys into human patients within two years to beat a national shortage of human donors.

But the Ministry of Health wants to ban animal-to-human transplants completely, pending further research, because the animal organs may introduce "retroviruses" into the human population - tiny particles that can get inside the genetic material in the cells of the human recipient and be passed on to that person's partner and descendants.

The Bioethics Council says the retroviruses may not cause any obvious signs of illness, but could be "switched on" suddenly later in the life of the transplant recipient or a descendant, or even in people in close contact with that person.

"The recipient may then pass the infection on to close contacts (medical staff, family and friends, co-workers), which in the worst-case scenario could result in a pandemic [disease affecting a whole country or the world]," it says.

"There is a serious problem in assessing this risk.

"On the one hand, there have been no reported instances of cross-species infections in the hundreds of xenotransplantations carried out.

"On the other hand, the consequences of getting it wrong are so serious it would seem morally irresponsible to assume that because there have been no reported problems so far everything will continue to be fine."

It suggests that transplant recipients could be asked to sign a contract, or be subject to special laws, allowing them to be quarantined in the event of a public health emergency and subject to other restrictions.