The Three Rs (3Rs) are guiding principles for more ethical use of animals in product testing and scientific research. They were first described by W. M. S. Russell and R. L. Burch in 1959. [1] The 3Rs are:
The 3Rs have a broader scope than simply encouraging alternatives to animal testing, but aim to improve animal welfare and scientific quality where the use of animals cannot be avoided. In many countries, these 3Rs are now explicit in legislation governing animal use. It is usual to capitalise the first letter of each of the three 'R' principles (i.e. 'Replacement' rather than 'replacement') to avoid ambiguity and clarify reference to the 3Rs principles.
In 1954, the Universities Federation for Animal Welfare (UFAW) decided to sponsor systematic research on the progress of humane techniques in the laboratory. [2] In October of that year, William Russell, described as a brilliant young zoologist who happened to be also a psychologist and a classical scholar, and Rex Burch, a microbiologist, were appointed to inaugurate a systematic study of laboratory techniques in their ethical aspects. In 1956, they prepared a general report to the Federation's committees, and this report formed the nucleus of the book which was completed at the beginning of 1958. Over much of the period they worked with a special Consultative Committee, chaired by Professor Peter Medawar.
As a contribution to the centenary of The Origin of Species , the quotations at the head of each chapter are all from the works of Charles Darwin.
A common misconception of the 3Rs is that they refer only to replacement; [3] however, their scope is much broader. Moreover, while the 3Rs were designed for research on laboratory animal models, their implementation has been encouraged also in farmed animals [4] [5] and wildlife conservation research. [6] [7]
Replacement: In the original book, the 3Rs were restricted, arbitrarily, to vertebrates. Russell and Burch discussed the possibility of suffering with reference to sentience. They used the term "replacement technique" for any scientific method using non-sentient material to replace methods which use conscious living vertebrates. [1] This non-sentient material included higher plants, microorganisms, and the more degenerate metazoan endoparasites which, they argued, had nervous and sensory systems that were almost atrophied. They acknowledged that the arbitrary exclusion of invertebrates meant that in several contexts, these species could be considered as possible replacements for vertebrate subjects; they termed this "comparative substitution". Russell and Burch also considered levels of replacement. In "relative replacement", animals are still required, though during an experiment they are exposed, probably or certainly, to no distress at all. In "absolute replacement", animals are not required at all at any stage.
Replacement strategies include:
More recent interpretations of the replacement principle suggest the preferred use of non-animal methods over animal methods whenever it is possible to achieve the same scientific aims, i.e. invertebrates are not considered suitable replacements for vertebrates. However, others such as the National Centre for the Replacement, Refinement and Reduction of Animals in Research (NC3Rs) advocate the use of some invertebrates in replacement studies. [8] Therefore, the term 'Replacement' can refer to the use of a supposedly less sentient species, [9] as in "relative replacement".
Russell and Burch writing six decades ago could not have anticipated some of the technologies that have emerged today. One of these technologies, 3D cell cultures, also known as organoids or mini-organs, have replaced animal models for some types of research. In recent years, scientists have produced organoids that can be used to model disease and test new drugs. Organoids grow in vitro on scaffolds (biological or synthetic hydrogels such as Matrigel) or in a culture medium. [10] Organoids are derived from three kinds of human or animal stem cells—embryonic pluripotent stem cells (ESCs), adult somatic stem cells (ASCs), and induced pluripotent stem cells (iPSCs). These organoids are grown in vitro and mimic the structure and function of different organs such as the brain, liver, lung, kidney, and intestine. Organoids have been developed to study infectious disease. Scientists at Johns Hopkins University have developed mini-brain organoids to model how COVID-19 can affect the brain. [11] Researchers have used brain organoids to model how the Zika virus disrupt fetal brain development. Tumoroids—3D cell cultures derived from cells biopsied from human patients—can be used in studying the genomics and drug resistance of tumors in different organs. Organoids are also used in modeling genetic diseases such as cystic fibrosis, [12] neurodegenerative diseases such as Alzheimer's and Parkinson's, infectious diseases such as MERS-CoV and norovirus, and parasitic infections such as Toxoplasma gondii. [10] Human- and animal-cell-derived organoids are also used extensively in pharmacological and toxicological research. [13] [14]
Reduction: Reduction refers to methods which minimise the number of animals used per study. [8] Russell and Burch suggested a reduction in the number of animals used could be achieved in several ways. One general way in which great reduction may occur is by the right choice of strategies in the planning and performance of whole lines of research. A second method is by controlling variation amongst the animals used in studies, and a third method is careful design and analysis of studies. With the advent, development and availability of computers since the original 3Rs, large data-sets can be used in statistical analysis, thereby reducing the numbers of animals used. In some cases, by using previously published studies, the use of animals can be totally avoided by avoiding unnecessary replication. Modern imaging techniques in conjunction with new statistical analysis methods also allow reductions in the numbers of animals used, for example, by providing greater information per animal. [15] [16]
Refinement: Russell and Burch wrote "Suppose, for a particular purpose, we cannot use replacing techniques. Suppose it is agreed that we shall be using every device of theory and practice to reduce to a minimum the number of animals we have to employ. It is at this point that refinement starts, and its object is simply to reduce to an absolute minimum the amount of distress imposed on those animals that are still used." [1] Amongst areas of experiments that can be refined are the procedure to be used, the appropriateness of the species (its suitability for the procedure and its responses to a laboratory environment in general).
Refinements techniques may include: [17]
The definition of Refinement has evolved from that provided by Russell and Burch. A newer definition is now commonly accepted: "any approach which avoids or minimises the actual or potential pain, distress and other adverse effects experienced at any time during the life of the animals involved, and which enhances their wellbeing." [18] Refinement encompasses not only the direct harms associated with animal use, but the indirect, or contingent harms associated with breeding, transportation, housing and husbandry.
Some have criticized the Three Rs for what they call "ambiguities" and tensions in the understanding and implementation of different prongs of the approach –Refinement, Reduction and Replacement. [19] This is, in part, because different stakeholders (e.g. animal experimenters, institutional figures, policy makers, activists and the public) may interpret the Three Rs differently. [19] [20] The 3Rs principles do not address some issues, such as the ethics of using animals in research and focus instead on improving the humane use of animals which are used. [19]
Others have noted that promotion of the 3Rs has failed to reduce the number of animals used in experiments. [21] [22] However, this may be the result of a misunderstanding of the definition of 'Reduction', not an absolute reduction in the number of animals used, but a reduction in the number of animals used per study. By its nature, it is difficult to estimate the number of animals not used in scientific procedures as a result of Replacement or Reduction techniques however, despite the rapid increases in medical research, animal numbers have not increased at the same rate. [23]
In a review of dozens of articles involving mice in prolonged pain experiments, researchers found "there were no references to the '3Rs'" which in turn "raise serious questions about whether the 3Rs' principles of Replacement, Reduction, and Refinement are being appropriately implemented by researchers and institutions". The researchers continued, [24]
That the 3Rs or any of the 3Rs' components—Replace, Reduce, or Refine—were not mentioned in any of the... studies suggests that prolonged mouse pain researchers may be unaware of or indifferent to the 3Rs framework and that this aspect is not considered relevant in the peer review process of manuscripts for scientific journals... [T]he growing proportion of the number of studies...in this paper suggests that adherence to guidelines and/or animal use committee requirements is not translating into significant progress from a reduction or replacement perspective.
Following a review of the quality of experimental design in published journal articles, [25] including the use of the 3Rs, it was found that the use and reporting of these principles was sporadic. As a result, the ARRIVE (Animal Research: Reporting of In Vivo Experiments) guidelines were developed [26] and published in 2010. The ARRIVE guidelines present a 20-point list of items which must be reported in publications which have used animals in scientific research, including sample size calculations, explicit descriptions of the environmental enrichment employed and welfare-related assessments made during the study. Many journals now require authors to comply with the ARRIVE guidelines in the preparation of manuscripts. [27] A follow-up review published in 2014 [28] found that there were still low reporting levels of some elements, such as reporting of appropriate statistical methods and the avoidance of bias.
In a survey of scientists in Portugal who had recently undergone training in the Three Rs, researchers found that a "surprisingly large number of researchers were unaware of the 3Rs principle, even those who had worked with animal models for over 10 years" and that subsequent training in the Three Rs "did not change perceptions on the current and future needs for animal use in research", but did increase knowledge of the application of the 3Rs [29] The authors found that the training they provided "appear to have little influence on researchers' acceptance of replacement alternatives to animal use". [29]
There are a number of organisations which promote the implementation of the 3Rs and methods that avoid the use of animals in research. Amongst the earliest is FRAME (the Fund for the Replacement of Animals in Medical Experiments) in the UK, established in 1969. The ZEBET (Zentralstelle zur Erfassung und Bewertung von Ersatz- und Ergänzungsmethoden zum Tierversuch) was founded in Germany in 1989, as the first governmental institution with the mandate to reduce animal experiments on a scientific basis. The United Kingdom's Home Office led the Inter-Departmental Group on Reduction, Refinement and Replacement, which aims to improve the application of the 3Rs and promote research into alternatives, reducing the need for toxicity testing through better sharing of data, and encouraging the validation and acceptance of alternatives.The Group reported to Ministers that there was support for a body which would act as a means to better publicise and coordinate what is already done by way of research into the 3Rs. In May 2004, the NC3Rs was announced in the UK to act as a focal point for research into the 3Rs. [30] Although the principles of the 3Rs were implicit in UK law under the Animals (Scientific Procedures) Act (1986), the Directive 2010/63/EU governing animal use within the European Union [31] makes the principles explicit and researchers must demonstrate the use of Replacement, Reduction and Refinement techniques in research involving animals. The Directive introduced a new level of transparency to help progress towards eventually replacing animal use in science and was instrumental in accelerating the concrete application of the 3Rs and the establishment of institutions and centres dedicated to dissemination, education and research based on the Principles across Europe. To date there are such centres in Austria, Belgium, Denmark, Germany, Ireland, Italy, Luxembourg, The Netherlands, Norway, Span, Sweden and Switzerland. [32]
Animal testing, also known as animal experimentation, animal research, and in vivo testing, is the use of non-human animals, such as model organisms, in experiments that seek to control the variables that affect the behavior or biological system under study. This approach can be contrasted with field studies in which animals are observed in their natural environments or habitats. Experimental research with animals is usually conducted in universities, medical schools, pharmaceutical companies, defense establishments, and commercial facilities that provide animal-testing services to the industry. The focus of animal testing varies on a continuum from pure research, focusing on developing fundamental knowledge of an organism, to applied research, which may focus on answering some questions of great practical importance, such as finding a cure for a disease. Examples of applied research include testing disease treatments, breeding, defense research, and toxicology, including cosmetics testing. In education, animal testing is sometimes a component of biology or psychology courses.
The Johns Hopkins University Center for Alternatives to Animal Testing (CAAT) has worked with scientists, since 1981, to find new methods to replace the use of laboratory animals in experiments, reduce the number of animals tested, and refine necessary tests to eliminate pain and distress. CAAT is an academic, science-based center affiliated with the Johns Hopkins Bloomberg School of Public Health.
An animal model is a living, non-human, often genetic-engineered animal used during the research and investigation of human disease, for the purpose of better understanding the disease process without the risk of harming a human. Although biological activity in an animal model does not ensure an effect in humans, many drugs, treatments and cures for human diseases are developed in part with the guidance of animal models. Animal models representing specific taxonomic groups in the research and study of developmental processes are also referred to as model organisms. There are three main types of animal models: Homologous, Isomorphic and Predictive. Homologous animals have the same causes, symptoms and treatment options as would humans who have the same disease. Isomorphic animals share the same symptoms and treatments, only. Predictive models are similar to a particular human disease in only a couple of aspects. However, these are useful in isolating and making predictions about mechanisms of a set of disease features.
Alternatives to animal testing are the development and implementation of test methods that avoid the use of live animals. There is widespread agreement that a reduction in the number of animals used and the refinement of testing to reduce suffering should be important goals for the industries involved. Two major alternatives to in vivo animal testing are in vitro cell culture techniques and in silico computer simulation; however, some claim they are not true alternatives because simulations use data from prior animal experiments and cell cultures often require animal derived products, such as serum or cells. Others say that they cannot replace animals completely as they are unlikely to ever provide enough information about the complex interactions of living systems.
Michael Balls is a British zoologist and professor emeritus of medical cell biology at the University of Nottingham. He is best known for his work on laboratory animal welfare and alternatives to animal testing.
Animal ethics is a branch of ethics which examines human-animal relationships, the moral consideration of animals and how nonhuman animals ought to be treated. The subject matter includes animal rights, animal welfare, animal law, speciesism, animal cognition, wildlife conservation, wild animal suffering, the moral status of nonhuman animals, the concept of nonhuman personhood, human exceptionalism, the history of animal use, and theories of justice. Several different theoretical approaches have been proposed to examine this field, in accordance with the different theories currently defended in moral and political philosophy. There is no theory which is completely accepted due to the differing understandings of what is meant by the term ethics; however, there are theories that are more widely accepted by society such as animal rights and utilitarianism.
Tatsuji Nomura was a pioneer in the development of laboratory animals with the aim of assuring reproducibility of experimental results in medical research. He was Director of the Central Institute for Experimental Animals (CIEA), Japan
Fund for the Replacement of Animals in Medical Experiments (FRAME) is a charity based in Nottingham, UK. FRAME funds and promotes alternatives to animal testing.
The Basel Declaration is a call for greater transparency and communication on the use of animals in research. It is supported by an international scientific non profit society, the Basel Declaration Society, a forum of scientists established to foster the greatest dissemination and acceptance of the Declaration, and the dialogue with the public and stakeholders.
European Partnership for Alternative Approaches to Animal Testing (EPAA) promotes the application of the 3Rs principles in meeting regulatory requirements for products such as pharmaceuticals, chemicals, soaps, detergents and cosmetics. The EPAA covers research and development, as well as the use of 3Rs approaches in regulatory compliance and communication and dissemination.
In New Zealand, animals are used in many situations for research, testing and teaching (RTT).
Rise for Animals is a national, registered 501(c)(3) nonprofit animal rights organization which aims to end nonhuman animal experimentation. It has been described as "one of the oldest and wealthiest anti-vivisection organizations in the United States".
The Universities Federation for Animal Welfare (UFAW) is an animal welfare science society. It is a UK-registered scientific and educational charity.
A Designated Member Review (DMR) or Designated Subcommittee Review (DSR), also known as Designated Review, is a review of a protocol where a committee designates one or more members of the committee to review a decisionmaking process or a protocol or procedure, a review which would ordinarily require the full committee's review. Typically this pertains to IACUCs.
The Institute for Laboratory Animal Research (ILAR) is a United States organization which develops and shares information and guidelines about animal testing and care of laboratory animals. It is a unit in the United States National Research Council. Their mission is "to evaluate and to report on scientific, technological, and ethical use of animals and related biological resources, and of non-animal alternatives in non-food settings, such as research, testing, education, and production of pharmaceuticals".
Directive 2010/63/EU is the European Union (EU) legislation "on the protection of animals used for scientific purposes" and is one of the most stringent ethical and welfare standards worldwide.
ALTEX: Alternatives to Animal Experimentation is a quarterly peer-reviewed scientific journal covering alternatives to animal experimentation and related issues of bioethics, seeking to promote the replacement, reduction, and refinement of animal use in research. It was originally published in German and established in 1984 as ALTEX: Alternativen zu Tierexperimenten and is published by Springer Spektrum on behalf of the Swiss Society ALTEX Edition.
William Moy Stratton Russell, also known as Bill Russell, was a British zoologist and animal welfare worker. He was best known for writing, along with R. L. Burch (1926-1996) The Principles of Humane Experimental Technique (1959), a landmark in the humane use of animals in research, education and testing. Russell and Burch introduced the concept of the Three Rs in the scientific community and provided a blueprint for combining animal welfare considerations and quality of research.
Uwe Marx is a German physician and biotechnologist, and one of the world’s leading researchers in the fields of organ-on-a-chip technology and antibody production.
The National Centre for the Replacement, Refinement and Reduction of Animals in Research is a British organization with the goal of reducing the number of animals used in scientific research. It is named after the three Rs principles, first described in 1959, for reducing the scale and impact of animal research. It was established in 2004 after the publication of a 2002 House of Lords select committee report on Animals In Scientific Procedures As of 2021, the chief executive of NC3Rs is Dr Vicky Robinson, who was appointed CBE in the 2015 Birthday Honours "For services to Science and Animal Welfare".