Animal testing or animal research is the use of non-human animals in scientific experimentation. It is estimated that 50 to 100 million vertebrate animals worldwide — from zebrafish to non-human primates — are used annually. Although much larger numbers of invertebrates are used and the use of flies and worms as model organisms is very important, experiments on invertebrates are largely unregulated and not included in statistics. Most animals are euthanized after being used in an experiment. Sources of laboratory animals vary between countries and species; while most animals are purpose-bred, others may be caught in the wild or supplied by dealers who obtain them from auctions and pounds.
The research is conducted inside universities, medical schools, pharmaceutical companies, farms, defense establishments, and commercial facilities that provide animal-testing services to industry. 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 topic is highly controversial. Supporters of the practice, 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, 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 some areas. The U.S. and British governments both support the advancement of medical and scientific goals using animal testing, provided that the testing minimizes animal use and suffering. Others, such as the British Union for the Abolition of Vivisection, question the necessity of it, these opponents make a range of arguments: that it is cruel, poor scientific practice, cannot reliably predict effects in humans, poorly regulated, that the costs outweigh the benefits, or that animals have an intrinsic right not to be used for experimentation.
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. Galen, a physician in second-century Rome, dissected pigs and goats, and is known as the "father of vivisection."
Animals have been used throughout the history of scientific research. In the 1880s, Louis Pasteur convincingly demonstrated the germ theory of medicine by inducing anthrax in sheep. In the 1890s, Ivan Pavlov famously used dogs to describe classical conditioning. Insulin was first isolated from dogs in 1922, and revolutionized the treatment of diabetes. 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, then given to humans. 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. This genetic research progressed rapidly and, in 1996, Dolly the sheep was born, the first mammal to be cloned from an adult cell.
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 a tragedy in 1937 where a drug labeled “Elixir of Sulfanilamide” killed more than 100 people, the U.S. congress passed laws that required safety testing of drugs on animals before they could be marketed. Other countries enacted similar legislation. 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.
The controversy surrounding animal testing dates back to the 17th century. In 1655, the advocate of Galenic physiology Edmund O'Meara said that "the miserable torture of vivisection places the body in an unnatural state." 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. 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.
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" and the father of physiology — whose wife, Marie Françoise Martin, founded the first anti-vivisection society in France in 1883 — 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". 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," Bernard established animal experimentation as part of the standard scientific method. 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.’ ” 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.
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. 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.
Mice, rats, and birds are not included in the provisions of the Animal Welfare Act (though they are included in the Guide) and over the years, the definition of "animal" used by Congress and the United States Department of Agriculture (USDA) has changed several times to ensure that certain animals are included in protective legislation and that others, particularly farm animals, are excluded.
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. The Nuffield Council on Bioethics reports that global annual estimates range from 50 to 100 million animals.
None of the figures, including those given in this article, include invertebrates, such as shrimp and fruit flies. Animals bred for research then killed as surplus, animals used for breeding purposes, and animals not yet weaned (which most laboratories do not count) are also not included in the figures.
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, but this does not include rats and mice, which make up about 90% of research animals. 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. 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.
In the UK, Home Office figures show that nearly three million procedures were carried out in 2004 on just under the same number of animals. It is the third consecutive annual rise and the highest figure since 1992. Most animals are used in only one procedure: animals either die because of the experiment or are euthanized afterwards. A "procedure" refers to an experiment that might last minutes, several months, or years.
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, while studies in the fly D. melanogaster can use an amazing array of genetic tools. 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. Similarly, flies are not widely used in applied medical research, as their immune system differs greatly from that of humans, and diseases in insects can be very different from diseases in more complex animals.
In the U.S., the numbers of rats and mice used is estimated at 20 million a year. 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. Mice are widely considered to be the best model of inherited human disease and share 99% of their genes with humans. 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. 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.
Nearly 200,000 fish and 20,000 amphibians were used in the UK in 2004. 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. 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. Rabbits are also frequently used for the production of polyclonal antibodies.
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 that had the potential to cause "pain and/or distress".
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. 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. 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.
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. 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. In total, around 70,000 NHPs are used each year in the United States and European Union. Most of the NHPs used are macaques; 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. The first transgenic primate was produced in 2001, with the development of a method that could introduce new genes into a rhesus macaque. This transgenic technology is now being applied in the search for a treatment for the genetic disorder Huntington's disease. 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.
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. 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. The USDA recovered at least a dozen stolen pets during a raid on a Class B dealer in Arkansas in 2003.
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.
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. 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. 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.
According to the U.S. Department of Agriculture, in 2006 about 670,000 animals (not including rats, mice, birds, or invertebrates) were used in procedures that did not include more than momentary pain or distress. About 420,000 were used in procedures in which pain or distress was relieved by anesthesia, while 84,000 were used in studies that would cause pain or distress that would not be relieved.
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, 39 percent (1,296) of project licenses in force were classified as mild, 55 percent (1,811) as moderate, two percent (63) as substantial, and 4 percent (139) as unclassified. Although there have been suggestions of systemic underestimation of procedure severity
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. Bernard Rollin of Colorado State University, the principal author of two U.S. federal laws regulating pain relief for animals, 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. 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. 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, some critics continue to question how reliably animal mental states can be determined. The ability of invertebrate species of animals, such as insects, to feel pain and suffering is also unclear.
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. 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.
Methods of euthanizing laboratory animals are chosen to induce rapid unconsciousness and death without pain or distress. 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.
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.
Examples of the types of animals and experiments used in basic research include:
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.
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."
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. 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. According to Nature, 5,000 animals are used for each chemical being tested, with 12,000 needed to test pesticides. The tests are conducted without anesthesia, because interactions between drugs can affect how animals detoxify chemicals, and may interfere with the results.
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.
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. Nature writes that, as of 2005, "the LD50 acute toxicity test ... still accounts for one-third of all animal [toxicity] tests worldwide." Irritancy is usually 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 recommended protocol involves observing the effects of the substance at intervals and grading any damage or irritation, but that the test should be halted and the animal killed if it shows "continuing signs of severe pain or distress". The Humane Society of the United States writes that the procedure can cause redness, ulceration, hemorrhaging, cloudiness, or even blindness. 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. 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, but it has not yet replaced the original test.
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". However, as Nature reported, most animal tests either over- or underestimate risk, or do not reflect toxicity in humans particularly well. 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. Although relationships do exist, opinion is divided on how to use data on one species to predict the exact level of risk in another.
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. The ban is also opposed by the European Federation for Cosmetics Ingredients, which represents 70 companies in Switzerland, Belgium, France, Germany and Italy.
Before the early 20th century, laws regulating drugs were lax. Nowadays all new pharmaceuticals undergo rigorous animal testing before being licensed for human use. Tests on pharmaceutical products involve:
There are efforts in many countries to find alternatives to using animals in education. 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.
A wide range of minority viewpoints exist as well. The view that animals have moral rights (animal rights) is a philosophical position proposed by Tom Regan, who argues that animals are beings with beliefs, desires and self-consciousness. Such beings are seen as having inherent value and thus possessing rights. Regan still sees clear ethical differences between killing animals and killing humans, and argues that to save human lives it is permissible to kill animals. However, some such as Bernard Rollin have taken his position further and argue that any benefits to human beings cannot outweigh animal suffering, and that human beings have no moral right to use an individual animal in ways that do not benefit that individual. Another prominent position is articulated by Peter Singer, who sees no convincing reason to include a being's species in considerations of whether their suffering is important in utilitarian moral considerations. Although these arguments have not been widely accepted, in response to these concerns some governments such as the Netherlands and New Zealand have outlawed invasive experiments on certain classes of non-human primates, particularly the Great Apes.
University of California, Riverside One of the cases of alleged abuse involved Britches, a macaque monkey born in 1985 at the University of California, Riverside, removed from its mother at birth, and left alone with its eyelids sewn shut, and a sonar sensor on its head, as part of an experiment to test sensory substitution devices for blind people. 260 animals, including Britches, were stolen from the laboratories at the University of California, Riverside in a raid by the Animal Liberation Front. The university alleged that damage to the monkey's eyelids, caused by the sutures according to the ALF, had in fact been caused by an ALF veterinarian, and that the sonar device had been removed and re-attached by the activists. The ALF reported that Britches was later transferred to a sanctuary in Mexico. University officials reported that hundreds of thousands of dollars of damage was done by the theft, and by smashing laboratory equipment, and years of medical research were lost.Columbia University CNN reported in October 2003 that a post-doctoral "whistleblowing" veterinarian at Columbia University approached the university's Institutional Animal Care and Use Committee about experiments being carried out by an assistant professor of neurosurgery, E. Sander Connolly. Connolly was allegedly causing strokes in baboons by removing their left eyeballs and using the eye sockets to reach a critical blood vessel to their brains. A clamp was placed on the blood vessel until the stroke was induced, after which Connolly would try to treat the condition with an experimental drug. In a letter to the National Institute of Health, PETA cited the case of a baboon they said was unable to sit up or eat, and remained slouched over in its cage, before dying two days later. An investigation by the United States Department of Agriculture found the experiments did not violate federal guidelines. Connolly abandoned the research saying he felt under attack after receiving a threatening e-mail, but continued to believe his experiments were humane and potentially valuable.
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. Such legislation, and the arrest and imprisonment of extremists may have decreased the incidence of attacks.
Although such principles have been welcomed as a step forwards by some animal welfare groups, they have also been criticized as both outdated by current research, and of little practical effect in improving animal welfare.