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What is xenotransplantation about?
Xenotransplantation is a surgery that involves the use of live cells, tissues and organs from a non-human animal source, transplanted into humans.

Talking about xenotransplantation is important because it raises key questions such as:
• Is it morally right to breed genetically modified animals to use their organs for human transplant?
• Is xenotransplantation acceptable or too risky?
• How long should we go on replacing organs and cells in a human life?

Author / translator Andrea Bandelli

What is xenotransplantation about?
Xenotransplantation is a surgery that involves the use of live cells, tissues and organs from a non-human animal source, transplanted into humans.

Talking about xenotransplantation is important because it raises key questions such as:
• Is it morally right to breed genetically modified animals to use their organs for human transplant?
• Is xenotransplantation acceptable or too risky?
• How long should we go on replacing organs and cells in a human life?
• Should xenotransplant patients and their families be subject ro restrictions from regulatory authorities in order to protect the population from potential virus spreading?
• How do we balance individual liberties and availability of medical treatment with the remote risk of an epidemic from transferring an animal virus into the human population?

Created 26 January 2010
Last edited 20 June 2018
Topics Ethics, Health, Science

Policy positions

Policy position 1

Do not transplant live animal organs into human patients for ethical and moral reasons

Policy position 2

Do not transplant live animal organs into human patients because it is too risky

Policy position 3

Only transplant animal organs into human patients if the benefits are sure and very large and if the benefits definitely outweigh the risks.

Policy position 4

Transplant animal organs into human patients provided the risks are shown to be reasonable.

Story cards


I am an animal technician. Its amazing how attached you can get to the pigs we breed. It is hard to see them go, but this has to be done. What would be really wrong would be to treat these animals badly just because we know that in the end they are going to be put down as part of an experiment. We owe it to them to care for them. I know it isn’t natural that they spend all their life indoors, and often in isolation, but I still think they have a good life.

Sophia’s story

I’ve worked for ten years to enable pig hearts to be successfully transplanted into humans. I’ve seen the terrible suffering at first hand of people born with congenital heart diseases. My son, Toby, was born with a weak heart. He could barely walk and couldn’t play with other children. We waited for a donated heart to be found, but he died before one was available. I don’t want other children and families to suffer in the same way that Toby suffered. That’s why I believe xenotransplantation is important.

Dr. Sharon Taylor

I’m waiting for a heart transplant. My heart has been dodgy for years, but a car accident last summer was such a shock to my system that it has been erratic ever since. Doctors say that the likelihood of finding a donor heart is slim. I’ve heard about xenotransplantation - transplanting a pig heart into humans. I am a vegetarian, and don’t want to do this, but the idea gets more appealing the longer I wait. I just want to watch my daughter grow up again and to be well.

Ben’s story

I’m a heart surgeon in a hospital. I specialise in heart transplantation. There are many people on the waiting list for donor organs, and most of them cannot lead a fully active life. I am interested in the use of pig hearts as alternatives to human hearts. Some patients would jump at the chance – if they could. My only worry is about the transfer of viruses. Following the HIV and CJD scares, its something we have to be careful of. We don’t want to unleash more disease on the world.

Dr. Dean Kusafuko

I’m 18. I’ve been travelling in South Africa for three months before going to college. It really upset me. So many people are dying of AIDS- related diseases. There are drugs available in the West that can help, but they don’t get sent. Condoms can prevent the spread of HIV, but they don’t get sent either! Why don’t people in the West do something to help? Why do scientists keep pouring money into new areas of research, like creating genetically modified pigs for organ donation? There are other ways to reduce human suffering, and better ways to spend money.

Hilda’s story

I live in New Delhi with my wife, Radha, who is a doctor, and my family. I believe that it is karma - the results of someone’s actions either in this life or a previous life – which causes birth defects, like congenital heart defects. Radha tells me that in the West, people want to put pig hearts into human beings! In the West, scientists try things for the sake of discovery and fame. Meanwhile, every day I see people starving, or crippled from diseases that are preventable. Why is this inequality allowed to continue?

Vishnu’s story

My son, who is 35 now, has a heart abnormality and nearly died at birth. He walks very slowly with a stick, and needs constant care. Although we are wealthy enough to try many remedies, none has helped. My son has been on the waiting list for a heart transplant for some years. I would do anything to see him happy and well. I have heard it might be possible to transplant pig hearts into humans. I hope the scientists succeed. Will it come in time to save my son though?

Nanou’s story

I was desperate for a new heart, and when they offered me one from a pig I jumped at it. Of course I’m pleased to feel better and to be able to do more. But the longer time passes, the worse I feel about having part of a pig inside me. If it was say a hip replacement made from the bone of a pig I wouldn’t mind, but the heart is different. I feel that while my body didn’t reject the heart physically, I have rejected it emotionally.

Anna in 2030


Don’t humans eat pigs anyway?

Some say if we kill pigs to eat, surely we should use their organs to save life? Others say it’s not the same - eating animals is natural, but using their organs is artificial.

What use of pigs should we allow?

Should we put human genes in pigs, or pig organs in humans? Should we allow pig cloning in order to delete certain genes?

Waiting lists

Currently, there are long waits for human organs, involving decline in health, considerable anxiety, and the loss of life. Supporters argue that enough animals could be reared to overcome this.

Ethnic minorities

Xenotransplantation would be particularly useful for people such as those from ethnic minorities for whom it is difficult to find compatible human organs.

Stopping the trade of organs

The buying and selling of human organs, especially kidneys, continues despite legislation in many countries prohibiting it. Successful xenotransplantation might help stop this.

An alternative to human tissues

Xenotransplantation might provide an alternative to the use of human tissue from aborted fetuses.

Accepting our mortality

Are we trying to cheat death? Is there a point where we should accept our mortality and stop replacing organs?

Using animals to treat humans?

How far are we justified in using animals in order to find therapies for humans?

An ethical dilemma

Is it wrong to create animals to remove their organs for transplantation?

Balancing risks

To a terminally ill patient offered a pig’s heart, virus risks may seem relatively small.

A risk of unknown proportions

Virus transfer risk to the population is very remote, but it could have very serious consequences, were it to occur.

Individuals versus society

How do we balance life and health for an individual patient or loved one against a wider risk to society?

The status of pigs

Does using pigs as organ donors, treating them as commodities for human use, encourage us to think that they only exist for human benefit?

When the risk is too big

In 2000, the UK Roslin Institute pulled out of xenotransplantation research because of the risk from spreading of retroviruses, concentrating instead on regenerating tissue from stem cells.

European acceptance

In a European poll, 36% of people found xenotransplantation acceptable.

A word of caution

“Nothing could be worse than if in trying to save our lives we engineered a plague.” Editorial in New Scientist magazine 1998

An undesirable side effect

The introduction of xenotransplantation will not eliminate the need for human organs, but it might reduce people’s willingness to donate them.

Patenting animals

Proposals to patent genetically modified pigs produced for xenotransplantation would increase the overall debate about the morality and legality of patenting animals.

Life in isolation

Keeping genetically modified pigs free from infection may imply a change in their living conditions and harm their welfare. They may be kept in isolation, or in a non-natural environment without the items which might enrich their lives.

Diseases without symptoms

Viral infections like HIV may have a long latent period when no symptoms appear. A new disease resulting from xenotransplantation might have several years to spread before it was identified.

When screening is too late

Pigs, monkeys and apes have unknown infectious organisms that will not be screened for. Infectious organisms are normally identified only after the emergence of the disease they cause.

Respecting ethical choices

Patients should be able to refuse a xenotransplant on ethical grounds, but their refusal should not affect their chances of getting a human organ for transplant.

The cost-benefit equation

The benefits from xenotransplantation should be compared to the cost to heath services. They should also be compared with the benefits from spending the same amount on public health programmes.

A new layer of responsibilities

The UK Xenotransplantation Interim Regulatory Authority has stated that anyone who receives a transplant of an animal organ would have to agree to lifetime monitoring and never have unprotected sex.

What is xenotransplantation?

Xenotransplantation covers:
• The transplant of whole organs
• Cell transplant therapies
• Bioartificial Liver Devices (BAL) – where pig liver cells are used to perform the essential functions of the natural liver.

Traditional transplants

Since the first heart transplants, live (human) organ transplantation has been the preferred approach to transplantation.

The organ gap

There are 5 patients waiting for an organ transplant for every organ donated. This shortfall is known as the ‘organ gap’. It is serious because there are not usually alternative treatments.

Life saving transplants

Sufferers from cystic fibrosis, an inherited disease, are unlikely to live beyond the age of thirty without a lung or heart-lung transplant.

Live donors

In Norway, the high kidney transplant rate is due to the high number of live donors giving kidneys.

Efficiency of donor campaigns

70 per cent of UK citizens are in favour of donating their organs after their death. But only a quarter carry donor cards. Publicity campaigns have not made much difference.

A way to solve the donor gap

Xenotransplantation could solve the shortage of organs for transplant (the ‘organ gap’), using pigs or primates organs (mainly apes and monkeys) because they are similar to humans in size and structure.

Are pigs better than monkeys?

Pigs are the preferred species as organ donors for humans because their organs are about the right size, they are relatively cheap and they pose fewer ethical concerns than using monkeys or apes.

Beyond organ transplants

As well as whole organs, there are studies on using nerve cells from pigs to treat Parkinson’s and Huntington’s disease.

Rejection problems

The difficulty with xenotransplantation is that the human immune system detects the new organ as ‘foreign’ and tries to kill it.

Improvements to transplants

The transplant of human organs has become more successful because immunosuppressive drugs inhibit rejection and because surgical techniques have improved.

Life expectancy after a transplant

Two-thirds of kidney recipients live for more than five years. There are examples of transplant patients whose lives have been extended by twenty years and more.

Lifelong therapy

Even patients with human organ transplants require lifelong immunosuppression drugs.

Genetically modified animals

To overcome rejection, scientists are genetically modifying animals, by removing the molecule that marks other species as foreign to the human immune system or by introducing human genes into pigs.

Spreading diseases across species

The transplanted organ could transfer a disease between species. The closer the species, the more likely this is. For this reason, pigs are considered safer than apes, but pig viruses have infected human cells in laboratory tests.

Hidden threats

Some viruses do not cause disease in the host species but may cause disease if they spread to another species.

Suppressing the immune system

Transplant patients have their immune system suppressed with drugs. This makes them vulnerable to the effects of retroviruses. Any infection could then spread to the wider population.

The advantage of cloning pigs

One approach is to delete a gene from pigs which normally triggers organ rejection. Gene ‘knockout’ can only be done using cloned pigs.

Earlier examples of cross-species diseases

Cross-species disease paths can occur. An HIV strain came originally from monkeys. Bovine Spongiform Encephalopathy (the “mad cow disease”) transferred to humans as Creutzfeldt-Jakob disease, a fatal illness. See info card 16

Virus transfer across species

Lab experiments have found some virus transfer from pig to human cells. However there is no evidence that pig heart valves or blood have transferred viruses to patients.

Alternatives to xenotransplantation 1

Prevention. This means healthier living to reduce heart disease. However, this cannot prevent many conditions which lead to the need for transplants.

Alternatives to xenotransplantation 2

Increasing organ donation. This could be done by an ‘opt out’ system: it would be assumed that people were willing to donate their organs after death unless they said otherwise.

Alternatives to xenotransplantation 3

Artificial organs, like a battery-powered heart, although these have their own problems, like blood clotting, and are very expensive.

Alternatives to xenotransplantation 4

Stem cells. Stem cells are master cells which can produce other types of cells. They could be used to produce heart or liver tissue to support failing organs.

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