The Big Issues - Background Summary

Animal-to-human transplantation: Should Canada proceed?


Xenotransplantation involves taking living cells, tissues or organs from one species of animal to another. This discussion is about transplanting from animals to humans.

“Xeno” is a Greek word meaning “stranger.” The “x” is pronounced like a “z” (zeeno).
  • Doctors transplant living cells, tissues and organs from one human to another human. These transplants are used to treat diseases or to keep people alive after one of their organs has stopped working.
  • Scientists are exploring transplanting animal cells, tissues and organs into humans. Organs include hearts, livers and kidneys. Cells and tissues might be used to treat diseases like diabetes, Alzheimer’s and Parkinson’s.
  • Transplanting animal cells, tissues and organs into humans raises a lot of questions. Is this a good way to save lives and cure people? Is it safe? Who should pay for it? Should humans use animals in this way?

This paper looks at eight key issues.

Issue #1:  Is xenotransplantation needed?

Organ Shortages

  • In 1999, there were 3,544 people on waiting lists for organs in Canada but only 1,667 received one (including 378 kidneys donated by living people). More than 3 out of 4 people on the waiting list needed a kidney. The rest were waiting for livers, hearts, lungs or pancreases.
  • About 3 out of 10 of these people die before an organ becomes available. It appears that the number of people waiting for organs will continue to grow as the number of people over the age of 60 grows.
  • Compared to some other countries, very few organs are donated for transplants in Canada. This is partly because fewer people die from car crashes and gunshots than in other countries.


  • Many people say Canada’s organ donation rate could be a lot higher. Perhaps more people would donate if they knew about the people on the waiting lists. Also, some of the organs that are donated are wasted because hospitals don’t have the time and money to get them to the people who need them.
  • Some countries have an organ donor policy called “presumed consent.” This means that instead of leaving it to people to make sure the government knows they want to donate their organs when they die, it is up to the people who do not want to donate to tell the government.
  • In some countries, human organs are sold. It is estimated that each year 200 to 300 Americans buy organs from poor people in developing countries. However, many people believe that selling human organs is wrong.
  • Different ways to cure diseases and keep people alive are being studied. For example, some researchers are trying to build better artificial organs, such as mechanical hearts. Others are trying to grow organs using stem cells (cells that can develop into any type of tissue). This is very new, however, and a lot more work is needed.
  • Preventing disease is one way to deal with the demand for organs, tissues and cells for transplant. Exercise, healthy eating and less alcohol and tobacco use are all ways to reduce disease and the need for organ transplants. These approaches take time, however, and there will still be people who need an organ, tissue or cell transplant to survive.

Issue #2:  Will xenotransplantation work?

  • Transplanting animal organs and tissues into humans has been tried many times in the past but most patients died soon after the transplant. The main problem has been “organ rejection.” The animal cells and organs are attacked and killed by the patient’s immune system.
  • Some drugs can suppress a patient’s immune system so that the transplant can survive. These drugs have been used with human-to-human transplants. However, transplanted animal organs are more foreign to a patient’s immune system and the drugs have not yet worked for xenotransplants.
  • Scientists are trying to make animal cells, tissues and organs more acceptable to humans by inserting human genes into animal cells. This is called “genetic modification.” Animals that carry human genes are called “transgenic” animals. Transgenic pigs have been developed and are being used for xenotransplantation research in Canada.
  • Scientists in Canada are now experimenting with xenotransplants between two different species of animals, such as from pigs to baboons. Some experts think it is time to try xenotransplants with people but others say it is too early.

Issue #3:  How far should we go to save a human life?

  • Xenotransplantation raises several questions. Is it interfering with nature? Does it change what it means to be human? These same questions were asked 40 years ago when human-to-human transplants were new.
  • The major religions do not have policies or formal opinions on xenotransplantation. It would seem that most religions would be willing to accept it if there is as little animal suffering as possible.
  • Some people disagree with genetically changing animals. (See “transgenic” animals, above.) Arguments against genetic modification are that boundaries exist between species for their protection and that we do not know what may result from this in the future.
  • Arguments for genetic modification are that it is just like animal breeding and selection and that genes change on their own over time.

Issue #4:  Is there a risk to the public?

  • No technology or medical procedure is risk free. Scientists do not yet know about all the risks of xenotransplantation. However, the biggest risk may be transferring animal diseases to patients, who may then transfer these diseases to other people. An animal infection transferred to humans is called “zoonosis.”
  • There is no evidence that past experiments of animal-to-human transplants led to zoonoses. However, most patients died before there was time to develop symptoms.
  • Scientists now know more about zoonotic infections. For example, HIV (which causes AIDS) almost certainly originated as an ape or monkey virus that infected humans. Scientists also know that “retroviruses” in animal cells can also infect human cells and exist for many years before any symptoms are shown.
  • Because animals like apes and monkeys are the most similar to humans, their diseases tend to be most easily transferred to humans. Apes, monkeys, humans, chimpanzees and baboons are called “primates.” Non-primates can also cause zoonotic infections. Ten patients with diabetes were transplanted with pig cells in Sweden in 1993. They developed antibodies to pig viruses but none has become sick from them.
  • Many scientists now think that pigs are the best animals to use for xenotransplantation. Pigs for xenotransplantation are being bred in germ-free laboratories but scientists have not been able to produce pigs with no viruses. Because drugs will be used to suppress a xenotransplant patient’s immune system, animal infections may easily survive in the patients. Transgenic pigs with human genes may transfer pig viruses and diseases to people more easily.
  • Today, it is impossible to say exactly what will or will not happen with xenotransplantation because scientists do not have all the answers. Some say the only way to get the answers is by carefully experimenting with human volunteers or “clinical trials.” Others do not think it is worth the risk to the public.

Issue #5:  What are the legal issues?

  • One of xenotransplantation’s major legal questions involves “informed consent.” This means that xenotransplantation volunteers would probably have to understand and agree to rules that would limit their freedom. The rules would try to protect the public from infectious diseases that may result from xenotransplantation.
  • No country has finalized these rules yet, but patients may have to agree to:
    • never travelling outside their country or region,
    • never having children,
    • identifying all their sexual partners to authorities,
    • never donating blood,
    • being monitored by authorities for as long as they live, and/or
    • having a post-mortem after death.
  • Because it could take years for a zoonotic disease to develop, patients would probably never be allowed to change their mind about agreeing to all the rules. New laws may have to be created to enforce these rules. Some experts believe the rules would be impossible to enforce.
  • Other legal questions include:
    • Who decides what risks are acceptable?
    • Who is responsible if something goes wrong?

Issue #6:  Is it okay to use animals in this way?

  • Primates, pigs, dogs, rabbits and rodents are currently being used in large numbers for xenotransplantation research all over the world.
  • Pigs are the first choice for xenotransplantation because they are easy to breed, have the right size of organs for humans and are less likely to transmit diseases than primates.
  • There are different opinions about how animals should be used by humans. Some people accept any use of animals, such as for food, labour, clothing and experiments. Some accept certain kinds of uses, such as for medical experiments but not cosmetic and chemical testing. Others feel that animals are not for humans to eat, experiment on or use for clothing or entertainment.
  • Opinion polls show that most people accept some use of animals, especially if they are not treated cruelly and there is a direct benefit to humans.
  • Animals being raised for xenotransplantation live in cages in sterile laboratories to reduce the risk of infection in humans.

Issue #7:  How much will xenotransplantation cost?

  • At this time, no one knows for sure how much xenotransplant would cost if it is accepted as a medical treatment for humans.
  • A xenotransplant would probably cost at least as much as other transplants. The cost of a kidney transplant in British Columbia is about $20,000 plus $6,000 a year for the anti-rejection drugs. The average cost of a heart transplant is said to be $80,000. Ontario spends about $47 million a year on organ transplants and that amount is expected to more than double in four years.
  • The cost of xenotransplants would also include the cost of breeding, feeding, housing and collecting the organs and tissues, as well as the cost of monitoring patients and studying the effects over time.
  • Xenotransplants may reduce the cost of treating people waiting for organ transplants. For example, transplanting a kidney costs less than dialysis treatment over five years.

Issue #8:  What regulations would be needed in Canada?

  • New laws and regulations would probably be needed if xenotransplantation becomes an accepted medical treatment.
  • Clinical trials of any kind (with human volunteers) can only take place with Health Canada’s permission. The decision is based on safety, quality, effectiveness and the expected results. The Minister of Health can ban xenotransplantation tests with human volunteers to protect the public health.
  • There are no Canadian laws that specifically protect animals used for xenotransplantation. Some provinces have laws about how animals can be used for research and experiments but there is no federal law. Canada’s Criminal Code has a provision that forbids “causing unnecessary pain, suffering, or injury to an animal or bird.”
  • The Canadian Environmental Protection Act (CEPA) investigates all new substances before they can be sold in Canada. This is to make sure new products are safe to the environment and human health. This would include animal tissues and organs for xenotransplantation.