About the authors: is University Research Professor, Philosophy at Dalhousie. is Associate Professor, Philosophy at Dalhousie.
At the end of 2021, 57-year old David Bennett Sr. was bedridden and on life-support with irreversible heart failure. He was not eligible for a human heart transplant or an implanted mechanical heart pump because of his underlying health condition and, allegedly, 鈥�.鈥�
Certain death was on the horizon and this fatal prognosis made Bennett a candidate for a highly experimental and never-before-attempted surgical procedure involving the transplantation of a heart from a genetically modified pig.
The pig-to-human cardiac transplant 鈥� or xenotransplant 鈥� was and the surgery was performed on Jan. 7, 2022.
Initial reports following the experimental surgery suggested that .
Bennett died on March 8 鈥� at the time, 鈥渘o obvious cause鈥� of death was identified. Now, it has been reported that the pig heart was .
Though the cause of death remains unclear, infection has been implicated in previous xenotransplantation failures involving baboons as the recipients.
More demand than supply
There is an ongoing chronic . Indeed, many .
Attempts to increase the limited supply of human organs have included changes to consent rules: , and, in some countries, .
Still, patients die on transplant waiting lists. For this reason, there is ever increasing interest in xenotransplantation 鈥� an ethically controversial practice.
Nonhuman primates and pigs
In 1984, , an infant born with a fatal heart defect called . Baby Fae lived for three weeks, but eventually died of heart failure caused by rejection of the transplanted baboon heart.
Prior to this, there had been three other experimental nonhuman heart transplants, .
More recent efforts at xenotransplantation have involved the . The most dramatic recent example, however, remains Bennett鈥檚 first-in-human cardiac xenotransplant using a genetically modified pig heart.
For some, the use of pig hearts for xenotransplantation may be ethically preferable to the use of nonhuman primate hearts because pigs are already used for medicine: for example, .
Or it could be that pigs are preferable 鈥渙rgan donors鈥� because they are already used for food. When it comes to food animals 鈥� those who are consumed by humans 鈥� people can be biased against accurately seeing the subjectivity of the animal. This is referred to as the 鈥�,鈥� where people perceive food animals as 鈥�.鈥�
A third reason to prefer killing pigs for human benefit instead of killing nonhuman primates is that pigs are biologically less similar to humans.
Prioritizing humans
Moral worth 鈥� 鈥� is not species specific. Rather, it is associated with specific capacities such as the ability to think, make choices, experience pain, communicate and have social relationships.
Because a human zygote lacks such capacities, not many believe that they have the same moral worth as a human two-year old, and there is nothing obviously irrational about this belief. Though a zygote may have the potential to reach a comparable level of development as a two-year old, they are not yet comparable. Their shared human identity is beside the point.
On occasion, humans may choose to prioritize the interests of their companion animals without doing something obviously wrong. For example, it is not irrational to spend money on the care of pets, even if that money could have gone towards helping fellow humans. This choice may reflect a shared social relationship and the emotional bonds that come with it. It may also reflect a sense of duty toward nonhuman animals that are dependent on the care provided by humans.
Having said this, clearly, there are times when it is appropriate to prioritize the interests of humans over other animals; it is just that . In any case, it is not clear, nor is it easy to determine, that Bennett鈥檚 extraordinary xenotransplant falls into this category.
Animal welfare
In Canada, support for animal-based research is anchored in a commitment to . The problem with this stance is that current animal welfare considerations do not typically support strong constraints on the scientific use of animals.
Notably, there are pressures to limit, but , the use of animals in research likely to have severe welfare impacts. Also, common animal welfare considerations do not prohibit killing the animals, they just constrain how they are killed.
Part of the problem here is that there are . The three Rs, which are pervasive in regulated animal use in science, emphasize replacing sentient animals (animals capable of experiencing pain and pleasure) where possible, reducing the number of sentient animals used in studies to a 鈥渂are minimum鈥� and refining their experiences of use to minimize suffering.
As such, the three Rs seem to assume something like a principled commitment to non-maleficence 鈥� . However, the continued dependency on harmful animal-based research that almost always ends with the killing of the animals belies this claim, given the known .
Given the ethical challenges with animal-based research in general and more specifically the ethical challenges with animal-to-human xenotransplantation, there is good reason to look for for transplantation.
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