Animal testing

Animal testing, also known as animal experimentation, animal research, and in vivo testing, is the use of non-human animals in experiments. Worldwide it is estimated that 50 to 100 million vertebrate animals are used annually—from zebrafish to non-human primates.^[1] Invertebrates, mice, rats, birds, fish, frogs, and animals not yet weaned are not included in the figures; one estimate of mice and rats used in the United States alone in 2001 was 80 million.^[2] Most animals are euthanized after being used in an experiment.^[3] Sources of laboratory animals vary between countries and species; most animals are purpose-bred, while others are caught in the wild or supplied by dealers who obtain them from auctions and pounds.^[4]

The research is conducted inside universities, medical schools, pharmaceutical companies, farms, defense establishments, and commercial facilities that provide animal-testing services to industry.^[5] It includes pure research such as genetics, developmental biology, behavioural studies, as well as applied research such as biomedical research, xenotransplantation, drug testing and toxicology tests, including cosmetics testing. Animals are also used for education, breeding, and defense research. The practice is regulated to various degrees in different countries.

Supporters of the use of animals in experiments, such as the British Royal Society, argue that virtually every medical achievement in the 20th century relied on the use of animals in some way,^[6] with the Institute for Laboratory Animal Research of the U.S. National Academy of Sciences arguing that even sophisticated computers are unable to model interactions between molecules, cells, tissues, organs, organisms, and the environment, making animal research necessary in many areas.^[7] A number of scientists, animal welfare, and animal rights organizations—such as PETA and BUAV—question the legitimacy of it, arguing that it is cruel, poor scientific practice, poorly regulated, that medical progress is being held back by misleading animal models, that some of the tests are outdated, that it cannot reliably predict effects in humans, that the costs outweigh the benefits, or that animals have an intrinsic right not to be used for experimentation.^[8]

Definitions

The terms animal testing, animal experimentation, animal research, in vivo testing, and vivisection have similar denotations but different connotations. Literally, "vivisection" means the "cutting up" of a living animal, and historically referred only to experiments that involved the dissection of live animals. The term is occasionally used to refer pejoratively to any experiment using living animals; for example, the Encyclopædia Britannica defines "vivisection" as: "Operation on a living animal for experimental rather than healing purposes; more broadly, all experimentation on live animals",^[9] although dictionaries point out that the broader definition is "used only by people who are opposed to such work".^[10] The word has a negative connotation, implying torture, suffering, and death.^[11] The word "vivisection" is preferred by those opposed to this research, whereas scientists typically use the term "animal experimentation".^[12][13]

History

An Experiment on a Bird in an Air Pump, from 1768, by Joseph Wright

The earliest references to animal testing are found in the writings of the Greeks in the second and fourth centuries BCE. Aristotle (Αριστοτέλης) (384-322 BCE) and Erasistratus (304-258 BCE) were among the first to perform experiments on living animals.^[14] Galen, a physician in second-century Rome, dissected pigs and goats, and is known as the "father of vivisection."^[15] Avenzoar, an Arabic physician in twelfth-century Moorish Spain who also practiced dissection, introduced animal testing as an experimental method of testing surgical procedures before applying them to human patients.^[16][17]

Animals have been used repeatedly through the history of biomedical research. In the 1880s, Louis Pasteur convincingly demonstrated the germ theory of medicine by inducing anthrax in sheep.^[18] In the 1890s, Ivan Pavlov famously used dogs to describe classical conditioning.^[19] Insulin was first isolated from dogs in 1922, and revolutionized the treatment of diabetes.^[20] On November 3, 1957, a Russian dog, Laika, became the first of many animals to orbit the earth. In the 1970s, antibiotic treatments and vaccines for leprosy were developed using armadillos,^[21] then given to humans.^[22] The ability of humans to change the genetics of animals took a large step forwards in 1974 when Rudolf Jaenisch was able to produce the first transgenic mammal, by integrating DNA from the SV40 virus into the genome of mice.^[23] This genetic research progressed rapidly and, in 1996, Dolly the sheep was born, the first mammal to be cloned from an adult cell.^[24]

Toxicology testing became important in the 20th century. In the 19th century, laws regulating drugs were more relaxed. For example, in the U.S., the government could only ban a drug after a company had been prosecuted for selling products that harmed customers. However, in response to the Elixir Sulfanilamide disaster of 1937 in which the eponymous drug killed more than 100 users, the U.S. congress passed laws that required safety testing of drugs on animals before they could be marketed. Other countries enacted similar legislation.^[25] In the 1960s, in reaction to the Thalidomide tragedy, further laws were passed requiring safety testing on pregnant animals before a drug can be sold.^[26]

Historical debate

Claude Bernard, regarded as the "prince of vivisectors"^[27] argued that experiments on animals are "entirely conclusive for the toxicology and hygiene of man".^[28]

As the experimentation on animals increased, especially the practice of vivisection, so did criticism and controversy. In 1655, the advocate of Galenic physiology Edmund O'Meara said that "the miserable torture of vivisection places the body in an unnatural state."^[29][30] O'Meara and others argued that animal physiology could be affected by pain during vivisection, rendering results unreliable. There were also objections on an ethical basis, contending that the benefit to humans did not justify the harm to animals.^[30] Early objections to animal testing also came from another angle — many people believed that animals were inferior to humans and so different that results from animals could not be applied to humans.^[30]

On the other side of the debate, those in favor of animal testing held that experiments on animals were necessary to advance medical and biological knowledge. Claude Bernard, known as the "prince of vivisectors"^[27] and the father of physiology—whose wife, Marie Françoise Martin, founded the first anti-vivisection society in France in 1883^[31]—famously wrote in 1865 that "the science of life is a superb and dazzlingly lighted hall which may be reached only by passing through a long and ghastly kitchen".^[32] Arguing that "experiments on animals ... are entirely conclusive for the toxicology and hygiene of man...the effects of these substances are the same on man as on animals, save for differences in degree,"^[28] Bernard established animal experimentation as part of the standard scientific method.^[33]

In 1896, the physiologist and physician Dr. Walter B. Cannon said “The antivivisectionists are the second of the two types Theodore Roosevelt described when he said, ‘Common sense without conscience may lead to crime, but conscience without common sense may lead to folly, which is the handmaiden of crime.’ ”^[34] These divisions between pro- and anti- animal testing groups first came to public attention during the brown dog affair in the early 1900s, when hundreds of medical students clashed with anti-vivisectionists and police over a memorial to a vivisected dog.^[35]

One of Pavlov’s dogs with a saliva-catch container and tube surgically implanted in his muzzle, Pavlov Museum, 2005

In 1822, the first animal protection law was enacted in the British parliament, followed by the Cruelty to Animals Act (1876), the first law specifically aimed at regulating animal testing. The legislation was promoted by Charles Darwin, who wrote to Ray Lankester in March 1871: "You ask about my opinion on vivisection. I quite agree that it is justifiable for real investigations on physiology; but not for mere damnable and detestable curiosity. It is a subject which makes me sick with horror, so I will not say another word about it, else I shall not sleep to-night."^[36][37] Opposition to the use of animals in medical research first arose in the United States during the 1860s, when Henry Bergh founded the American Society for the Prevention of Cruelty to Animals (ASPCA), with America's first specifically anti-vivisection organization being the American AntiVivisection Society (AAVS), founded in 1883. Antivivisectionists of the era generally believed the spread of mercy was the great cause of civilization, and vivisection was cruel. However, in the USA the antivivisectionists' efforts were defeated in every legislature, overwhelmed by the superior organization and influence of the medical community. Overall, this movement had little legislative success until the passing of the Laboratory Animal Welfare Act, in 1966.^[38]

Care and use of animals

Regulations

The regulations that apply to animals in laboratories vary across species. In the U.S., under the provisions of the Animal Welfare Act and the Guide for the Care and Use of Laboratory Animals (the Guide), published by the National Academy of Sciences, any procedure can be performed on an animal if it can be successfully argued that it is scientifically justified. In general, researchers are required to consult with the institution's veterinarian and its Institutional Animal Care and Use Committee (IACUC), which every research facility is obliged to maintain.^[39] The IACUC must ensure that alternatives, including non-animal alternatives, have been considered, that the experiments are not unnecessarily duplicative, and that pain relief is given unless it would interfere with the study. Larry Carbone, a laboratory animal veterinarian, writes that, in his experience, IACUCs take their work very seriously regardless of the species involved, though the use of non-human primates always raises what he calls a "red flag of special concern."^[40] A study published in Science magazine in July 2001 confirmed the low reliability of IACUC reviews of animal experiments. Funded by the National Science Foundation, the three-year study found that animal-use committees that do not know the specifics of the university and personnel do not make the same approval decisions as those made by animal-use committees that do know the university and personnel. Specifically, blinded committees more often ask for more information rather than approving studies.^[41]

The IACUCs regulate all vertebrates in testing at institutions receiving federal funds in the USA. Although the provisions of the Animal Welfare Act do not include purpose-bred rodents and birds, these species are equally regulated under Public Health Service policies that govern the IACUCs.^[42][43] Animal Welfare Act regulations are enforced by the USDA, whereas Public Health Service regulations are enforced by OLAW and in many cases by AAALAC.

Numbers

Types of vertebrates used in animal testing in Europe in 2005: a total of 12.1 million animals were used.^[44]

Accurate global figures for animal testing are difficult to obtain. The British Union for the Abolition of Vivisection (BUAV) estimates that 100 million vertebrates are experimented on around the world every year, 10–11 million of them in the European Union.^[45] The Nuffield Council on Bioethics reports that global annual estimates range from 50 to 100 million animals. None of the figures include invertebrates such as shrimp and fruit flies.^[46] Animals bred for research then killed as surplus, animals used for breeding purposes, and animals not yet weaned are also not included in the figures.^[47]

According to the U.S. Department of Agriculture (USDA), the total number of animals used in that country in 2005 was almost 1.2 million,^[48] but this does not include rats and mice, which make up about 90% of research animals.^[49][50] In 1995, researchers at Tufts University Center for Animals and Public Policy estimated that 14-21 million animals were used in American laboratories in 1992, a reduction from a high of 50 million used in 1970.^[51] In 1986, the U.S. Congress Office of Technology Assessment reported that estimates of the animals used in the U.S. range from 10 million to upwards of 100 million each year, and that their own best estimate was at least 17 million to 22 million.^[52]

In the UK, Home Office figures show that 3.2 million procedures were carried out in 2007, a rise of 189,500 since the previous year. Four thousand procedures used non-human primates, down 240 from 2006.^[53] A "procedure" refers to an experiment that might last minutes, several months, or years. Most animals are used in only one procedure: animals either die because of the experiment or are euthanized afterwards.^[46]

Species

Invertebrates

Fruit flies are commonly used.

Although many more invertebrates than vertebrates are used, these experiments are largely unregulated by law. The most used invertebrate species are Drosophila melanogaster, a fruit fly, and Caenorhabditis elegans, a nematode worm. In the case of C. elegans, the worm's body is completely transparent and the precise lineage of all the organism's cells is known,^[54] while studies in the fly D. melanogaster can use an amazing array of genetic tools.^[55] These animals offer great advantages over vertebrates, including their short life cycle and the ease with which large numbers may be studied, with thousands of flies or nematodes fitting into a single room. However, the lack of an adaptive immune system and their simple organs prevent worms from being used in medical research such as vaccine development.^[56] Similarly, flies are not widely used in applied medical research, as their immune system differs greatly from that of humans,^[57] and diseases in insects can be very different from diseases in vertebrates.^[58]

Vertebrates

A white Wistar lab rat

This rat is being deprived of restful REM sleep by a researcher using a single platform ("flower pot") technique. The water is within 1 cm of the small flower pot bottom platform where the rat sits. At the onset of REM sleep, the rat would either fall into the water only to clamber back to its pot to avoid drowning, or its nose would become submerged into the water shocking it back to an awakened state.

In the U.S., the numbers of rats and mice used is estimated at 20 million a year.^[50] Other rodents commonly used are guinea pigs, hamsters, and gerbils. Mice are the most commonly used vertebrate species because of their size, low cost, ease of handling, and fast reproduction rate.^[59] Mice are widely considered to be the best model of inherited human disease and share 99% of their genes with humans.^[59] With the advent of genetic engineering technology, genetically modified mice can be generated to order and can provide models for a range of human diseases.^[59] Rats are also widely used for physiology, toxicology and cancer research, but genetic manipulation is much harder in rats than in mice, which limits the use of these rodents in basic science.^[60]

Nearly 200,000 fish and 20,000 amphibians were used in the UK in 2004.^[61] The main species used is the zebrafish, Danio rerio, which are translucent during their embryonic stage, and the African clawed frog, Xenopus laevis. Over 20,000 rabbits were used for animal testing in the UK in 2004.^[61] Albino rabbits are used in eye irritancy tests because rabbits have less tear flow than other animals, and the lack of eye pigment in albinos make the effects easier to visualize.^[61] Rabbits are also frequently used for the production of polyclonal antibodies.

Cats and dogs

Cats are most commonly used in neurological research. Over 25,500 cats were used in the U.S. in 2000, around half of whom were used in experiments which, according to the American Anti-Vivisection Society, had the potential to cause "pain and/or distress".^[62]

Dogs are widely used in biomedical research, testing, and education — particularly beagles, because they are gentle and easy to handle. They are commonly used as models for human diseases in cardiology, endocrinology, and bone and joint studies, research that tends to be highly invasive, according to the Humane Society of the United States.^[63] The U.S. Department of Agriculture's Animal Welfare Report for 2005 shows that 66,000 dogs were used in USDA-registered facilities in that year.^[48] In the U.S., some of the dogs are purpose-bred, while most are supplied by so-called Class B dealers licensed by the USDA to buy animals from auctions, shelters, newspaper ads, and who are sometimes accused of stealing pets.^[64]

Non-human primates

Around 65,000 primates are used each year in the U.S. and Europe.

Non-human primates (NHPs) are used in toxicology tests, studies of AIDS and hepatitis, studies of neurology, behavior and cognition, reproduction, genetics, and xenotransplantation. They are caught in the wild or purpose-bred. In the U.S. and China, most primates are domestically purpose-bred, whereas in Europe the majority are imported purpose-bred.^[65] Rhesus monkeys, cynomolgus monkeys, squirrel monkeys, and owl monkeys are imported; around 12,000 to 15,000 monkeys are imported into the U.S. annually.^[66] In total, around 70,000 NHPs are used each year in the United States and European Union.^[44][48] Most of the NHPs used are macaques;^[67] but marmosets, spider monkeys, and squirrel monkeys are also used, and baboons and chimpanzees are used in the U.S; in 2006 there were 1133 chimpanzees in U.S. primate centers.^[68] The first transgenic primate was produced in 2001, with the development of a method that could introduce new genes into a rhesus macaque.^[69] This transgenic technology is now being applied in the search for a treatment for the genetic disorder Huntington's disease.^[70] Notable studies on non-human primates have been part of the polio vaccine development, and development of Deep Brain Stimulation, and their current heaviest non-toxicological use occurs in the monkey AIDS model, SIV.^[6][67][71] In 2008 a proposal to ban all primates experiments in the EU has sparked a vigorous debate.^[72]

Sources

Animals used by laboratories are largely supplied by specialist dealers. Sources differ for vertebrate and invertebrate animals. Most laboratories breed and raise flies and worms themselves, using strains and mutants supplied from a few main stock centers.^[73] For vertebrates, sources include breeders who supply purpose-bred animals; businesses that trade in wild animals; and dealers who supply animals sourced from pounds, auctions, and newspaper ads. Animal shelters also supply the laboratories directly.^[74] Large centers also exist to distribute strains of genetically-modified animals; the National Institutes of Health Knockout Mouse Project, for example, aims to provide knockout mice for every gene in the mouse genome.^[75]

A laboratory mouse cage. Mice are either bred commercially, or raised in the laboratory.

In the U.S., Class A breeders are licensed by the U.S. Department of Agriculture (USDA) to sell animals for research purposes, while Class B dealers are licensed to buy animals from "random sources" such as auctions, pound seizure, and newspaper ads. Some Class B dealers have been accused of kidnapping pets and illegally trapping strays, a practice known as bunching.^[76] It was in part out of public concern over the sale of pets to research facilities that the 1966 Laboratory Animal Welfare Act was ushered in — the Senate Committee on Commerce reported in 1966 that stolen pets had been retrieved from Veterans Administration facilities, the Mayo Institute, the University of Pennsylvania, Stanford University, and Harvard and Yale Medical Schools.^[77] The USDA recovered at least a dozen stolen pets during a raid on a Class B dealer in Arkansas in 2003.^[78]

Four states in the U.S. — Minnesota, Utah, Oklahoma, and Iowa — require their shelters to provide animals to research facilities. Fourteen states explicitly prohibit the practice, while the remainder either allow it or have no relevant legislation.^[79]

In the European Union, animal sources are governed by Council Directive 86/609/EEC, which requires lab animals to be specially bred, unless the animal has been lawfully imported and is not a wild animal or a stray. The latter requirement may also be exempted by special arrangement.^[80] In the UK, most animals used in experiments are bred for the purpose under the 1988 Animal Protection Act, but wild-caught primates may be used if exceptional and specific justification can be established.^[81][82] The United States also allows the use of wild-caught primates; between 1995 and 1999, 1,580 wild baboons were imported into the U.S. Over half the primates imported between 1995 and 2000 were handled by Charles River Laboratories, Inc., or by Covance, which is the single largest importer of primates into the U.S.^[83]

Pain and suffering

Prior to vivisection for educational purposes, chloroform was administered to this common sand frog to induce terminal anesthesia.

The extent to which animal testing causes pain and suffering, and the capacity of animals to experience and comprehend them, is the subject of much debate.^[84]

According to the U.S. Department of Agriculture, in 2006 about 670,000 animals (57%) (not including rats, mice, birds, or invertebrates) were used in procedures that did not include more than momentary pain or distress. About 420,000 (36%) were used in procedures in which pain or distress was relieved by anesthesia, while 84,000 (7%) were used in studies that would cause pain or distress that would not be relieved.^[48]

In the UK, research projects are classified as mild, moderate, and substantial in terms of the suffering the researchers conducting the study say they may cause; a fourth category of "unclassified" means the animal was anesthetized and killed without recovering consciousness, according to the researchers. In December 2001, 1,296 (39%) of project licenses in force were classified as mild, 1,811 (55%) as moderate, 63 (2%) as substantial, and 139 (4%) as unclassified.^[85] There have, however, been suggestions of systemic underestimation of procedure severity.^[86]

The idea that animals might not feel pain as human beings feel it traces back to the 17th-century French philosopher, René Descartes, who argued that animals do not experience pain and suffering because they lack consciousness.^[46][87] Bernard Rollin of Colorado State University, the principal author of two U.S. federal laws regulating pain relief for animals,^[88] writes that researchers remained unsure into the 1980s as to whether animals experience pain, and that veterinarians trained in the U.S. before 1989 were simply taught to ignore animal pain.^[89] In his interactions with scientists and other veterinarians, he was regularly asked to "prove" that animals are conscious, and to provide "scientifically acceptable" grounds for claiming that they feel pain.^[89] Carbone writes that the view that animals feel pain differently is now a minority view. Academic reviews of the topic are more equivocal, noting that although the argument that animals have at least simple conscious thoughts and feelings has strong support,^[90] some critics continue to question how reliably animal mental states can be determined.^[46][91] The ability of invertebrate species of animals, such as insects, to feel pain and suffering is also unclear.^[92][93]

The defining text on animal welfare regulation, "Guide for the Care and Use of Laboratory Animals" defines the parameters that govern animal testing in the USA. It states "The ability to experience and respond to pain is widespread in the animal kingdom...Pain is a stressor and, if not relieved, can lead to unacceptable levels of stress and distress in animals."^[94] The Guide states that the ability to recognize the symptoms of pain in different species is vital in efficiently applying pain relief and that it is essential for the people caring for and using animals to be entirely familiar with these symptoms. On the subject of analgesics used to relieve pain, the Guide states "The selection of the most appropriate analgesic or anesthetic should reflect professional judgment as to which best meets clinical and humane requirements without compromising the scientific aspects of the research protocol". Accordingly, all issues of animal pain and distress, and their potential treatment with analgesia and anesthesia, are required regulatory issues in receiving animal protocol approval.

Euthanasia

There is general agreement that animal life should not be taken wantonly, and regulations require that scientists use as few animals as possible.^[95] However, while policy makers consider suffering to be the central issue and see animal euthanasia as a way to reduce suffering, others, such as the RSPCA, argue that the lives of laboratory animals have intrinsic value.^[96] Regulations focus on whether particular methods cause pain and suffering, not whether their death is undesirable in itself.^[97] The animals are euthanized at the end of studies for sample collection or post-mortem examination; during studies if their pain or suffering falls into certain categories regarded as unacceptable, such as depression, infection that is unresponsive to treatment, or the failure of large animals to eat for five days;^[98] or when they are unsuitable for breeding or unwanted for some other reason.^[99]

Methods of euthanizing laboratory animals are chosen to induce rapid unconsciousness and death without pain or distress.^[100] The methods that are preferred are those published by councils of veterinarians. The animal can be made to inhale a gas, such as carbon monoxide and carbon dioxide, by being placed in a chamber, or by use of a face mask, with or without prior sedation or anesthesia. Sedatives or anesthetics such as barbiturates can be given intravenously, or inhalant anesthetics may be used. Amphibians and fish may be immersed in water containing an anesthetic such as tricaine. Physical methods are also used, with or without sedation or anesthesia depending on the method. Recommended methods include decapitation (beheading) for small rodents or rabbits. Cervical dislocation (breaking the neck or spine) may be used for birds, mice, and immature rats and rabbits. Maceration (grinding into small pieces) is used on 1 day old chicks. High-intensity microwave irradiation of the brain can preserve brain tissue and induce death in less than 1 second, but this is currently only used on rodents. Captive bolts may be used, typically on dogs, ruminants, horses, pigs and rabbits. It causes death by a concussion to the brain. Gunshot may be used, but only in cases where a penetrating captive bolt may not be used. Some physical methods are only acceptable after the animal is unconscious. Electrocution may be used for cattle, sheep, swine, foxes, and mink after the animals are unconscious, often by a prior electrical stun. Pithing (inserting a tool into the base of the brain) is usable on animals already unconscious. Slow or rapid freezing, or inducing air embolism are acceptable only with prior anesthesia to induce unconsciousness.^[101]

Research classification

Pure research

Basic or pure research investigates how organisms behave, develop, and function. Those opposed to animal testing object that pure research may have little or no practical purpose, but researchers argue that it may produce unforeseen benefits, rendering the distinction between pure and applied research—research that has a specific practical aim—unclear.^[102] Pure research uses larger numbers and a greater variety of animals than applied research. Fruit flies, nematode worms, mice and rats together account for the vast majority, though small numbers of other species are used, ranging from sea slugs through to armadillos.^[103] Examples of the types of animals and experiments used in basic research include:

• Studies on embryogenesis and developmental biology. Mutants are created by adding transposons into their genomes, or specific genes are deleted by gene targeting.^[104][105] By studying the changes in development these changes produce, scientists aim to understand both how organisms normally develop, and what can go wrong in this process. These studies are particularly powerful since the basic controls of development, such as the homeobox genes, have similar functions in organisms as diverse as fruit flies and man.^[106][107]

• Experiments into behavior, to understand how organisms detect and interact with each other and their environment, in which fruit flies, worms, mice, and rats are all widely used.^[108][109] Studies of brain function, such as memory and social behavior, often use rats and birds.^[110][111] For some species, behavioral research is combined with enrichment strategies for animals in captivity because it allows them to engage in a wider range of activities.^[112]

• Breeding experiments to study evolution and genetics. Laboratory mice, flies, fish, and worms are inbred through many generations to create strains with defined characteristics.^[113] These provide animals of a known genetic background, an important tool for genetic analyses. Larger mammals are rarely bred specifically for such studies due to their slow rate of reproduction, though some scientists take advantage of inbred domesticated animals, such as dog or cattle breeds, for comparative purposes. Scientists studying how animals evolve use many animal species to see how variations in where and how an organism lives (their niche) produce adaptations in their physiology and morphology. As an example, sticklebacks are now being used to study how many and which types of mutations are selected to produce adaptations in animals' morphology during the evolution of new species.^[114][115]

Applied research

Applied research aims to solve specific and practical problems. Compared to pure research, which is largely academic in origin, applied research is usually carried out in the pharmaceutical industry, or by universities in commercial partnerships. These may involve the use of animal models of diseases or conditions, which are often discovered or generated by pure research programmes. In turn, such applied studies may be an early stage in the drug discovery process. Examples include:

• Genetic modification of animals to study disease. Transgenic animals have specific genes inserted, modified or removed, to mimic specific conditions such as single gene disorders, such as Huntington's disease.^[116] Other models mimic complex, multifactorial diseases with genetic components, such as diabetes,^[117] or even transgenic mice that carry the same mutations that occur during the development of cancer.^[118] These models allow investigations on how and why the disease develops, as well as providing ways to develop and test new treatments.^[119] The vast majority of these transgenic models of human disease are lines of mice, the mammalian species in which genetic modification is most efficient.^[59] Smaller numbers of other animals are also used, including rats, pigs, sheep, fish, birds, and amphibians.^[82]

• Studies on models of naturally occurring disease and condition. Certain domestic and wild animals have a natural propensity or predisposition for certain conditions that are also found in humans. Cats are used as a model to develop immunodeficiency virus vaccines and to study leukemia because their natural predisposition to FIV and Feline leukemia virus.^[120] Certain breeds of dog suffer from narcolepsy making them the major model used to study the human condition. Armadillos and humans are among only a few animal species that naturally suffer from leprosy; as the bacteria responsible for this disease cannot yet be grown in culture, armadillos are the primary source of bacilli used in leprosy vaccines.^[121]

• Studies on induced animal models of human diseases. Here, an animal is treated so that it develops pathology and symptoms that resemble a human disease. Examples include restricting blood flow to the brain to induce stroke, or giving neurotoxins that cause damage similar to that seen in Parkinson's disease.^[122] Such studies can be difficult to interpret, and it is argued that they are not always comparable to human diseases.^[123] For example, although such models are now widely used to study Parkinson's disease, the British anti-vivisection interest group BUAV argues that these models only superficially resemble the disease symptoms, without the same time course or cellular pathology.^[124] In contrast, scientists assessing the usefulness of animal models of Parkinson's disease, as well as the medical research charity The Parkinson's Appeal, state that these models were invaluable and that they led to improved surgical treatments such as pallidotomy, new drug treatments such as levodopa, and later deep brain stimulation.^{[71][122][125]}

Xenotransplantation

Xenotransplantation research involves transplanting tissues, or organs from one species to another, as a way to overcome the shortage of human organs for use in organ transplants.^[126] Current research involves using primates as the recipients of organs from pigs that have been genetically-modified to reduce the primates' immune response against the pig tissue.^[127] Although transplant rejection remains a problem,^[127] recent clinical trials that involved implanting pig insulin-secreting cells into diabetics did reduce these people's need for insulin.^[128][129]

The British Home Office released figures in 1999 showing that 270 monkeys had been used in xenotransplantation research in Britain during the previous four years. Documents leaked from Huntingdon Life Sciences to The Observer in 2003 showed, between 1994 and 2000, wild baboons were imported to the UK from Africa to be used in experiments that involved grafting pigs' hearts and kidneys onto the primates' necks, abdomens, and chests. The Observer reports that some baboons died after suffering strokes, vomiting, diarrhea, and paralysis, while others died en route to the UK. The experiments were conducted by Imutran Ltd, a subsidiary of Novartis Pharma AG in conjunction with Cambridge University and Huntingdon Life Sciences. Novartis told the newspaper that developing new cures for humans invariably means experimenting on live animals.^[86] The newspaper also wrote that researchers were deliberately underestimating the suffering in order to obtain licences. A report from Imutran said: "The Home Office will attempt to get the kidney transplants classified as 'moderate,' ensuring that it is easier for Imutran to receive a licence and ignoring the 'severe' nature of these programmes."^[86][130]

Toxicology testing

Toxicology testing, also known as safety testing, is conducted by pharmaceutical companies testing drugs, or by contract animal testing facilities, such as Huntingdon Life Sciences, on behalf of a wide variety of customers.^[131] According to 2005 EU figures, around one million animals are used every year in Europe in toxicology tests; which are about 10% of all procedures.^[44] According to Nature, 5,000 animals are used for each chemical being tested, with 12,000 needed to test pesticides.^[132] The tests are conducted without anesthesia, because interactions between drugs can affect how animals detoxify chemicals, and may interfere with the results.^[133][134]

A rabbit during a Draize test

Toxicology tests are used to examine finished products such as pesticides, medications, food additives, packing materials, and air freshener, or their chemical ingredients. Most tests involve testing ingredients rather than finished products, but according to BUAV, manufacturers believe these tests overestimate the toxic effects of substances; they therefore repeat the tests using their finished products to obtain a less toxic label.^[131]

The substances are applied to the skin or dripped into the eyes; injected intravenously, intramuscularly, or subcutaneously; inhaled either by placing a mask over the animals and restraining them, or by placing them in an inhalation chamber; or administered orally, through a tube into the stomach, or simply in the animal's food. Doses may be given once, repeated regularly for many months, or for the lifespan of the animal.

There are several different types of acute toxicity tests. The LD50 ("Lethal Dose 50%") test is used to evaluate the toxicity of a substance by determining the dose required to kill 50% of the test animal population. This test was removed from OECD international guidelines in 2002, replaced by methods such as the fixed dose procedure, which use fewer animals and cause less suffering.^[135][136] Nature writes that, as of 2005, "the LD50 acute toxicity test ... still accounts for one-third of all animal [toxicity] tests worldwide."^[132] Irritancy can be measured using the Draize test, where a test substance is applied to an animal's eyes or skin, usually an albino rabbit. For Draize eye testing, the test involves observing the effects of the substance at intervals and grading any damage or irritation, but the test should be halted and the animal killed if it shows "continuing signs of severe pain or distress".^[137] The Humane Society of the United States writes that the procedure can cause redness, ulceration, hemorrhaging, cloudiness, or even blindness.^[138] This test has also been criticized by scientists for being cruel and inaccurate, subjective, over-sensitive, and failing to reflect human exposures in the real world.^[139] Although no accepted in vitro alternatives exist, a modified form of the Draize test called the low volume eye test may reduce suffering and provide more realistic results and this was adopted as the new standard in September 2009.^[140][141] However, the Draize test will still be used for substances that are not severe irritants.^[141]

The most stringent tests are reserved for drugs and foodstuffs. For these, a number of tests are performed, lasting less than a month (acute), one to three months (subchronic), and more than three months (chronic) to test general toxicity (damage to organs), eye and skin irritancy, mutagenicity, carcinogenicity, teratogenicity, and reproductive problems. The cost of the full complement of tests is several million dollars per substance and it may take three or four years to complete.

These toxicity tests provide, in the words of a 2006 United States National Academy of Sciences report, "critical information for assessing hazard and risk potential".^[142] Nature reported that most animal tests either over- or underestimate risk, or do not reflect toxicity in humans particularly well,^[132] with false positive results being a particular problem.^[143] This variability stems from using the effects of high doses of chemicals in small numbers of laboratory animals to try to predict the effects of low doses in large numbers of humans.^[144] Although relationships do exist, opinion is divided on how to use data on one species to predict the exact level of risk in another.^[145]

Cosmetics testing

Products in Europe not tested on animals carry this symbol.

Cosmetics testing on animals is particularly controversial. Such tests, which are still conducted in the U.S., involve general toxicity, eye and skin irritancy, phototoxicity (toxicity triggered by ultraviolet light) and mutagenicity.^[146]

Cosmetics testing is banned in the Netherlands, Belgium, and the UK, and in 2002, after 13 years of discussion, the European Union (EU) agreed to phase in a near-total ban on the sale of animal-tested cosmetics throughout the EU from 2009, and to ban all cosmetics-related animal testing. France, which is home to the world's largest cosmetics company, L'Oreal, has protested the proposed ban by lodging a case at the European Court of Justice in Luxembourg, asking that the ban be quashed.^[147] The ban is also opposed by the European Federation for Cosmetics Ingredients, which represents 70 companies in Switzerland, Belgium, France, Germany and Italy.^[147]

Drug testing

Beagles used for safety testing of pharmaceuticals in a British facility

Before the early 20th century, laws regulating drugs were lax. Currently, all new pharmaceuticals undergo rigorous animal testing before being licensed for human use. Tests on pharmaceutical products involve:

• metabolic tests, investigating pharmacokinetics - how drugs are absorbed, metabolized and excreted by the body when introduced orally, intravenously, intraperitoneally, intramuscularly, or transdermally.

• toxicology tests, which gauge acute, sub-acute, and chronic toxicity. Acute toxicity is studied by using a rising dose until signs of toxicity become apparent. Current European legislation demands that "acute toxicity tests must be carried out in two or more mammalian species" covering "at least two different routes of administration".^[148] Sub-acute toxicity is where the drug is given to the animals for four to six weeks in doses below the level at which it causes rapid poisoning, in order to discover if any toxic drug metabolites build up over time. Testing for chronic toxicity can last up to two years and, in the European Union, is required to involve two species of mammals, one of which must be non-rodent.^[149]
• efficacy studies, which test whether experimental drugs work by inducing the appropriate illness in animals. The drug is then administered in a double-blind controlled trial, which allows researchers to determine the effect of the drug and the dose-response curve.
• Specific tests on reproductive function, embryonic toxicity, or carcinogenic potential can all be required by law, depending on the result of other studies and the type of drug being tested.

Education, breeding, and defense

Animals are also used for education and training; are bred for use in laboratories; and are used by the military to develop weapons, vaccines, battlefield surgical techniques, and defensive clothing.^[102] For example, in 2008 the United States Defense Advanced Research Projects Agency used live pigs to study the effects of improvised explosive device explosions on internal organs, especially the brain.^[150]

There are efforts in many countries to find alternatives to using animals in education.^[151] Horst Spielmann, German director of the Central Office for Collecting and Assessing Alternatives to Animal Experimentation, while describing Germany's progress in this area, told German broadcaster ARD in 2005: "Using animals in teaching curricula is already superfluous. In many countries, one can become a doctor, vet or biologist without ever having performed an experiment on an animal."^[152]

Ethics

Background

Monument for animals used in testing at Keio University

The ethical questions raised by performing experiments on animals are subject to much debate, and viewpoints have shifted significantly over the 20th century.^[153] There remain disagreements about which procedures are useful for which purposes, as well as disagreements over which ethical principles apply to which species. The dominant ethical position worldwide is that achievement of scientific and medical goals using animal testing is desirable, so long as animal suffering and use is minimized.^[154] The British government has additionally required that the cost to animals in an experiment be weighed against the gain in knowledge.^[155] Some medical schools and agencies in China, Japan, and South Korea have built cenotaphs for killed animals.^[156] In Japan there are also annual memorial services (Ireisai 慰霊祭) for animals sacrificed at medical school.

A wide range of minority viewpoints exist. The view that animals have moral rights (animal rights) is a philosophical position proposed by Tom Regan, among others, who argues that animals are beings with beliefs and desires, and as such are the "subjects of a life" with moral value and therefore moral rights.^[157] Regan still sees ethical differences between killing human and non-human animals, and argues that to save the former it is permissible to kill the latter. Others, such as Bernard Rollin, argue that benefits to human beings cannot outweigh animal suffering, and that human beings have no moral right to use an animal in ways that do not benefit that individual. Another prominent position is that of philosopher Peter Singer, who argues that there are no grounds to include a being's species in considerations of whether their suffering is important in utilitarian moral considerations.^[158]

Although these arguments have not been widely accepted, governments such as the Netherlands and New Zealand have responded to the concerns by outlawing invasive experiments on certain classes of non-human primates, particularly the great apes.^[159]

Prominent cases

Various specific cases of animal testing have drawn attention, including both instances of beneficial scientific research, and instances of alleged ethical violations by those performing the tests.

Muscle physiology

The fundamental properties of muscle physiology were determined with on work done using frog muscles (including the force generating mechanism of all muscle,^[160] the length-tension relationship,^[161] and the force-velocity curve^[162]), and frogs are still the preferred model organism due to the long survival of muscles in vitro and the possibility of isolating intact single-fiber preparations (not possible in other organisms).^[163] Modern physical therapy and the understanding and treatment of muscular disorders is based on this work and subsequent work in mice (often engineered to express disease states such as muscular dystrophy).^[164]

University of California, Riverside

1985 was a pivotal year in the debate about animal research in the United States, with the enactment of amendments to the Animal Welfare Act.^[165] Britches, a macaque monkey, was born that year inside the University of California, Riverside, removed from his mother at birth, and left alone with his eyelids sewn shut, and a sonar sensor on his head, as part of an experiment to test sensory substitution devices for blind people. The Animal Liberation Front raided the laboratory on April 20, 1985, removing Britches and 466 other animals, and reportedly inflicting $700,000-worth of damage to equipment.^[166] A spokesman for the university said the allegations of mistreatment were false, and that the raid caused long-term damage to its research projects.^[167] The National Institutes of Health conducted an eight-month investigation and concluded that no corrective action was necessary.^[168]

Huntingdon Life Sciences

Footage filmed by PeTA inside Huntingdon Life Sciences showed staff mistreating beagles.

In 1997, People for the Ethical Treatment of Animals filmed staff inside Huntingdon Life Sciences (HLS) in the UK, Europe's largest animal-testing facility, hitting puppies, shouting at them, and simulating sex acts while taking blood samples.^[169] The company said the employees were dismissed.^[170] Two pleaded guilty to "cruelly terrifying dogs," and were given community service orders and ordered to pay £250 costs, the first lab technicians to have been prosecuted for animal cruelty in the UK.^[171] The broadcast of the video on Britain's Channel 4 Television in March 1997 triggered the formation of Stop Huntingdon Animal Cruelty (SHAC), an international leaderless resistance campaign to close HLS, which has been criticized for its sometimes violent tactics.^[172] In January 2009, several British SHAC activists were jailed for blackmailing companies linked to HLS.^[173]

Roslin Institute

Dolly the sheep: the first clone produced from an adult animal

In February 1997 a team at the Roslin Institute in Scotland announced the birth of Dolly the sheep, a ewe that had been cloned from tissue taken from another adult sheep.^[24] Dolly was produced through nuclear transfer to an unfertilised oocyte, and was the only lamb that survived from 277 attempts at this technique.^[174] Dolly appeared to be a normal sheep, living for six years and giving birth to several lambs, but was euthanized in 2003 after contracting a progressive lung disease.^[175] Although the production of Dolly was a scientific breakthrough, it was controversial, since it showed that not only could cloned animals be produced for use in farming,^[176] but also that it would now be, in principle, possible to clone a human being.^[177]

University of Cambridge

A marmoset after being brain damaged, filmed at Cambridge by the BUAV

The British Union for the Abolition of Vivisection (BUAV) raised concerns about primate experiments at the University of Cambridge in 2002. In a series of court cases, the BUAV alleged that monkeys had undergone surgery to induce a stroke, and were left alone after the procedure for 15 hours overnight. Researchers had trained the monkeys to perform certain tasks before inflicting brain damage and re-testing them. The monkeys were only given food and water for two hours a day, to encourage them to perform the tasks. The judge hearing BUAV's application for a judicial review rejected the allegation that the Home Secretary had been negligent in granting the university a license.^[178] The British government's chief inspector of animals conducted a review of the facilities and experiments. It concluded the veterinary input at Cambridge was "exemplary"; the facility "seems adequately staffed"; and the animals afforded "appropriate standards of accommodation and care."^[179]

Columbia University

CNN reported in October 2003 that Catherine Dell'Orto, a veterinarian at Columbia University, had approached the university's Institute of Comparative Medicine about the treatment of baboons who were undergoing surgery as part of an experiment into stroke treatment. She said the baboons, who were in some cases having an eyeball removed, were left to suffer in their cages after the surgery. She alleged there was systemic maltreatment, poor record-keeping, and other violations of regulations, according to CNN. She presented her evidence in October 2002 and, dissatisfied with the response, contacted People for the Ethical Treatment of Animals two months later.^[180]

In March 2003, a lab technician shot video inside the lab, which according to The New York Daily News showed primates in cages without pain medication; the video included one baboon with a metal cylinder screwed into its head, according to the newspaper. Dell'Orto told the newspaper that primates were often not euthanized or given painkillers after surgery; she said other primates had torn their fingers off out of fear.^[181] The U.S. Department of Agriculture upheld Dell'Orto's complaint that there was shoddy record-keeping, and that 11 animals had been provided with "inadequate or questionable care." They found no evidence that the experiments violated federal guidelines or that there had been retaliation against Dell'Orto. CNN reported that Columbia responded by ordering better record-keeping, a review of the veterinary care program, and tighter criteria for euthanasia of laboratory animals.^[182]

Covance

In 2004, German journalist Friedrich Mülln shot undercover footage of staff in Covance, Münster, Europe's largest primate-testing center, making monkeys dance in time to blaring pop music, handling them roughly, and screaming at them. The monkeys were kept isolated in small wire cages with little or no natural light, no environmental enrichment, and high noise levels from staff shouting and playing the radio^[183] (video). Primatologist Jane Goodall described the living conditions of the monkeys as horrendous. Another primatologist, Stephen Brend, told BUAV that using monkeys in such a stressed state is bad science, and trying to extrapolate useful data in such circumstances is what he called an untenable proposition.^[183] In 2004 and 2005, PETA shot footage inside the company in the United States. According to The Washington Post, PETA said an employee of the group filmed primates being choked, hit, and denied medical attention when badly injured.^[184] The U.S. Department of Agriculture fined Covance $8,720 for 16 citations, three of which involved lab monkeys; the other citations involved administrative issues and equipment.^[185]

Threats to researchers

In 2006, a primate researcher at the University of California, Los Angeles (UCLA) shut down the experiments in his lab after threats from animal rights activists. The researcher had received a grant to use 30 macaque monkeys for vision experiments; each monkey was anesthetized for a single physiological experiment lasting up to 120 hours, and then euthanized.^[186] The researcher's name, phone number, and address were posted on the website of the Primate Freedom Project. Demonstrations were held in front of his home. A Molotov cocktail was placed on the porch of what was believed to be the home of another UCLA primate researcher; instead, it was accidentally left on the porch of an elderly woman unrelated to the university. The Animal Liberation Front claimed responsibility for the attack.^[187] As a result of the campaign, the researcher sent an email to the Primate Freedom Project stating "you win," and "please don’t bother my family anymore."^[188] In another incident at UCLA in June 2007, the Animal Liberation Brigade placed a bomb under the car of a UCLA children's ophthalmologist who experiments on cats and rhesus monkeys; the bomb had a faulty fuse and did not detonate.^[189] UCLA is now refusing Freedom of Information Act requests for animal medical records.

These attacks, as well as similar incidents that caused the Southern Poverty Law Center to declare in 2002 that the animal rights movement had "clearly taken a turn toward the more extreme," this prompted the US government to pass the Animal Enterprise Terrorism Act and the UK government to add the offense of "Intimidation of persons connected with animal research organisation" to the Serious Organised Crime and Police Act 2005.^[190] Such legislation, and the arrest and imprisonment of extremists may have decreased the incidence of attacks.^[191]

Alternatives to animal testing

Scientists and governments state that animal testing should cause as little suffering to animals as possible, and that animal tests should only be performed where necessary. The "three Rs"^[95] are guiding principles for the use of animals in research in most countries:

1. Replacement refers to the preferred use of non-animal methods over animal methods whenever it is possible to achieve the same scientific aim.
2. Reduction refers to methods that enable researchers to obtain comparable levels of information from fewer animals, or to obtain more information from the same number of animals.
3. Refinement refers to methods that alleviate or minimize potential pain, suffering or distress, and enhance animal welfare for the animals still used.^[192]

Although such principles have been welcomed as a step forwards by some animal welfare groups,^[193] they have also been criticized as both outdated by current research,^[194] and of little practical effect in improving animal welfare.^[195]

See also

• Preclinical imaging
• Bateson's cube
• Human subject research
• The People's Petition

Notes

Further reading and external links

Animal testing Main articles Animal testing · Alternatives to animal testing · Animal testing on invertebrates · Animal testing on frogs · Animal testing on non-human primates · Animal testing on rabbits · Animal testing on rodents · Animal testing regulations · History of animal testing · History of model organisms · Laboratory animal sources · Toxicology testing Issues Animal rights · Animal welfare · Pain and suffering in laboratory animals · Biomedical research · Animals (Scientific Procedures) Act 1986 · Great Ape research ban · International trade in primates Controversial experiments Brown Dog affair · Britches · Cambridge University primates · Pit of despair · Silver Spring monkeys · Unnecessary Fuss Companies Charles River Laboratories, Inc. · Covance · Harlan · Huntingdon Life Sciences · Laboratory animal suppliers in the United Kingdom · Nafovanny · Shamrock Farm Groups/campaigns Americans for Medical Progress · American Association for Laboratory Animal Science · American Association for the Advancement of Science · Boyd Group · British Union for the Abolition of Vivisection · Dr Hadwen Trust · Foundation For Biomedical Research · National Anti-Vivisection Society · People for the Ethical Treatment of Animals (PETA) · ALF · Physicians Committee for Responsible Medicine · Primate Freedom Project · Pro-Test · SPEAK · Research Defence Society · SHAC · Stop Sequani Animal Testing Writers/activists Colin Blakemore · Carl Cohen · Gill Langley · Ingrid Newkirk · Neal Barnard · Jerry Vlasak · Simon Festing · Tipu Aziz Categories Animal testing · Animal rights

Animal rights Activists Greg Avery · David Barbarash · Mel Broughton · Rod Coronado · Barry Horne · Ronnie Lee · Keith Mann · Ingrid Newkirk · Heather Nicholson · Jill Phipps · Craig Rosebraugh · Henry Spira · Andrew Tyler · Jerry Vlasak · Paul Watson · Robin Webb Writers Carol Adams · Jeremy Bentham · Steven Best · Stephen R. L. Clark · Gary Francione · Robert Garner · Gill Langley · Andrew Linzey · Mary Midgley · Tom Regan · Bernard Rollin · Richard D. Ryder · Henry Salt · Peter Singer · Syed Ziaur Rahman · Steven M. Wise · Roger Yates Groups Animal Aid · Animal Legal Defense Fund · Animal Liberation Brigade · Animal Liberation Front · Animal Liberation Press Office · Animal Rights Militia · BUAV · The Coalition to Abolish the Fur Trade · Friends of Animals · Great Ape Project · Hunt Saboteurs Association · Justice Department · PETA · Physicians Committee for Responsible Medicine · Primate Freedom Project · Sea Shepherd · SPEAK · SHAC Political parties Animal Alliance · Animals Count · Animal Protection Party · Party Against Bullfighting, Cruelty and Mistreatment to Animals · Party for the Animals · Tierschutzpartei Issues Abolitionism · Animal Enterprise Terrorism Act · Animals (Scientific Procedures) Act · Animal model · Animal protectionism · Animal testing · Animal testing on non-human primates · Anti-hunting · Bile bear · Blood sport · Covance · Ethics of eating meat · Factory farming · Fur trade · Great ape research ban · Green Scare · Huntingdon Life Sciences · International trade in primates · Meat industry · Nafovanny · Open rescue · Operation Backfire · Pain and suffering in laboratory animals · Recreational fishing · Seal hunting · Speciesism · Veganarchism · Veganism · Vegetarianism Cases Brown Dog affair · Britches · Cambridge University primates · McLibel case · Pit of despair · Silver Spring monkeys · Unnecessary Fuss Films, books and magazines The Cove (2009) · Behind the Mask (2006) · Earthlings (2006) · Peaceable Kingdom (2004) · The Animals Film (1981) · Animal Liberation (1975) · Arkangel · Bite Back · No Compromise Categories Animal Liberation Front · Animal rights movement · Animal rights · Animal testing · Blood sports · Famous animals · Livestock · Poultry