had not been resolved. this was repealed in 2009 after an nhmrc review stated "... the risks, if appropriately regulated, are minimal and acceptable given the potential benefits.", citing international developments on the management and regulation of xenotransplantation by the world health organisation and the european medicines agency. porcine endogenous retroviruses endogenous retroviruses are remnants of ancient viral infections, found in the genomes of most, if not all, mammalian species. integrated into the chromosomal dna, they are vertically transferred through inheritance. due to the many deletions and mutations they accumulate over time, they usually are not infectious in the host species, however the virus may become infectious in another species. pervs were originally discovered as retrovirus particles released from cultured porcine kidney cells. most breeds of swine harbor approximately 50 perv genomes in their dna. although it is likely that most of these are defective, some may be able to produce infectious viruses so every proviral genome must be sequenced to identify which ones pose a threat. in addition, through complementation and genetic recombination, two defective perv genomes could give rise to an infectious virus. there are three subgroups of infectious pervs (perv-a, perv-b, and perv-c). experiments have shown that perv-a and perv-b can infect human cells in culture. to date no experimental xenotransplantations have demonstrated perv transmission, yet this does not mean perv infections in humans are impossible. pig cells have been engineered to inactivate all 62 pervs in the genome using crispr cas9 genome editing technology, and eliminated infection from the pig to human cells in culture. ethics xenografts have been a controversial procedure since they were first attempted. many, including animal rights groups, strongly oppose killing animals to harvest their organs for human use. in the 1960s, many organs came from the chimpanzees, and were transferred into people that were deathly ill, and in turn, did not live much longer afterwards. modern scientific supporters of xenotransplantation argue that the potential benefits to society outweigh the risks, making pursuing xenotransplantation the moral choice. none of the major religions object to the use of genetically modified pig organs for life-saving transplantation. religions such as buddhism and jainism, however, have long espoused non-violence towards all living creatures. in general, the use of pig and cow tissue in humans has been met with little resistance, save some religious beliefs and a few philosophical objections. experimentation without consent doctrines are now followed, which was not the case in the past, which may lead to new religious guidelines to further medical research on pronounced ecumenical guidelines. the "common rule" is the united states bio-ethics mandate as of 2011. history of xenotransplantation in ethics at the beginning of the 20th century when studies in xenotransplantation were just beginning, few questioned the morality of it, turning to animals as a "natural" alternative to allografts. while satirical plays mocked xenografters such as serge voronoff, and some images showing emotionally distraught primates appeared - who voronoff had deprived of their testicles - no serious attempts were yet made to question the science based on animal rights concerns. xenotransplantation was not taken seriously, at least in france, during the first half of the 20th century. with the baby fae incident of 1984 as the impetus, animal rights activists began to protest, gathering media attention and proving that some people felt that it was unethical and a violation of the animal's own rights to use its organs to preserve a sick human's life. treating animals as mere tools for the slaughter on demand by human will would lead to a world they would not prefer. supporters of the transplant pushed back, claiming that saving a human life justifies the sacrifice of an animal one. most animal rights activists found the use of primate organs more reprehensible than those of, for example, pigs. as peter singer et al. have expressed, many primates exhibit greater social structure, communication skills, and affection than mentally deficient humans and human infants. despite this, it is considerably unlikely that animal suffering will provide sufficient impetus for regulators to prevent xenotransplantation. informed consent of patient autonomy and informed consent are important when considering the future uses of xenotransplantation. a patient undergoing xenotransplantation should be fully aware of the procedure and should have no outside force influencing their choice. the patient should understand the risks and benefits of such a transplantation. however, it has been suggested that friends and family members should also give consent, because the repercussions of transplantation are high, with the potential of diseases and viruses crossing over to humans from the transplantation. close contacts are at risk for such infections. monitoring of close relations may also be required to ensure that xenozoonosis is not occurring. the question then becomes: does the autonomy of the patient become limited based on the willingness or unwillingness of friends and family to give consent, and are the principles of confidentiality broken? the safety of public health is a factor to be considered. if there is any risk to the public at all for an outbreak from transplantation there must be procedures in place to protect the public. not only does the recipient of the transplantation have to understand the risks and benefits, but society must also understand and consent to such an agreement. the ethics committee of the international xenotransplantation association points out one major ethical issue is the societal response to such a procedure. the assumption is that the recipient of the transplantation will be asked to undergo lifelong monitoring, which would deny the recipient the ability to terminate the monitoring at any time, which is in direct opposition of the declaration of helsinki and the us code of federal regulations. in 2007, xenotransplantation was banned under ethical grounds in all countries but argentina, russia and new zealand. since then, the practice has only been carried out to treatment for diabetes type 1 to serve as a substitute for insulin injections. the application of the four bioethics principal is found to be everywhere because it is now standardized in the moral conducts of a laboratory. the four principles emphasize on the informed consent, the hippocratic oath to do no harm, apply one's skill to help others, and protecting the rights of others to quality care. problems with xenotransplantation is that even though it has future medical benefits, it also has the serious risk of introducing and spreading the infectious diseases, into the human population. there have been guidelines that have been drafted by the government that have the purpose of forming the foundation of infectious disease surveillance. in the united kingdom, the guideline that were introduced state that first, "the periodic provision of bodily samples that would then be archived for epidemiological purposes;" second, "post-mortem analysis in case of death, the storage of samples post-mortem, and the disclosure of this agreement to their family;" third, "refrain from donating blood, tissue or organs;" fourth, "the use of barrier contraception when engaging in sexual intercourse;" fifth, keep both name and current address on register and to notify the relevant health authorities when moving abroad;" and lastly "divulge confidential information, including one's status as a xenotransplantation recipient to researchers, all health care professionals from whom one seeks professional services, and close contacts such as current and future sexual partners." with these guidelines in place the patient has to abide to these rules until either their lifetime or until the government determines that there is no need for public health safe guards. xenotransplantation guidelines in the united states the food and drug administration (fda) has also stated that if a transplantation takes place the recipient must undergo monitoring for the rest of that recipient's lifetime and waive their right to withdraw. the reason for requiring lifelong monitoring is due to the risk of acute infections that may occur. the fda suggests that a passive screening program should be implemented and should extend for the life of the recipient.