Animal testing
Animal testing, also known as animal experimentation, animal research, and in vivo testing, is the use of non-human animals, as model organisms, in experiments that seek answers to scientific and medical questions. 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.
Research using animal models has been central to most of the achievements of modern medicine. It has contributed to most of the basic knowledge in fields such as human physiology and biochemistry, and has played significant roles in fields such as neuroscience and infectious disease. The results have included the near-eradication of polio and the development of organ transplantation, and have benefited both humans and animals. From 1910 to 1927, Thomas Hunt Morgan's work with the fruit fly Drosophila melanogaster identified chromosomes as the vector of inheritance for genes, and Eric Kandel wrote that Morgan's discoveries "helped transform biology into an experimental science". Research in model organisms led to further medical advances, such as the production of the diphtheria antitoxin and the 1922 discovery of insulin and its use in treating diabetes, which was previously fatal. Modern general anaesthetics such as halothane were also developed through studies on model organisms, and are necessary for modern, complex surgical operations. Other 20th-century medical advances and treatments that relied on research performed in animals include organ transplant techniques, the heart-lung machine, antibiotics, and the whooping cough vaccine.
Animal testing is widely used to aid in research of human disease when human experimentation would be unfeasible or unethical. This strategy is made possible by the common descent of all living organisms, and the conservation of metabolic and developmental pathways and genetic material over the course of evolution. Performing experiments in model organisms allows for better understanding of the disease process without the added risk of harming an actual human. The species of the model organism is usually chosen so that it reacts to disease or its treatment in a way that resembles human physiology as needed. Biological activity in a model organism does not ensure an effect in humans, and care must be taken when generalizing from one organism to another. However, many drugs, treatments and cures for human diseases are developed in part with the guidance of animal models. Treatments for animal diseases have also been developed, including for rabies, anthrax, glanders, feline immunodeficiency virus, tuberculosis, Texas cattle fever, classical swine fever, heartworm, and other parasitic infections. Animal experimentation continues to be required for biomedical research, and is used with the aim of solving medical problems such as Alzheimer's disease, AIDS, multiple sclerosis, spinal cord injury, and other conditions in which there is no useful in vitro model system available.
The annual use of vertebrate animals—from zebrafish to non-human primates—was estimated at 192 million as of 2015. In the European Union, vertebrate species represent 93% of animals used in research, and 11.5 million animals were used there in 2011. The mouse is associated with many important biological discoveries of the 20th and 21st centuries, and by one estimate, the number of mice and rats used in the United States alone in 2001 was 80 million. In 2013, it was reported that mammals, fish, amphibians, and reptiles together accounted for over 85% of research animals. In 2022, a law was passed in the United States that eliminated the FDA requirement that all drugs be tested on animals.
Animal testing is regulated to varying degrees in different countries. In some cases it is strictly controlled while others have more relaxed regulations. There are ongoing debates about the [|ethics and necessity of animal testing]. Proponents argue that it has led to significant advancements in medicine and other fields while opponents raise concerns about cruelty towards animals and question its effectiveness and reliability. There are efforts underway to find alternatives to animal testing such as computer simulation models, organs-on-chips technology that mimics human organs for lab tests, microdosing techniques which involve administering small doses of test compounds to human volunteers instead of non-human animals for safety tests or drug screenings, positron emission tomography scans which allow scanning of the human brain without harming humans, comparative epidemiological studies among human populations, and simulators and computer programs for teaching purposes.
Definitions
The terms animal testing, animal experimentation, animal research, in vivo testing, and vivisection have similar denotations but different connotations. Literally, "vivisection" means "live sectioning" of an 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", although dictionaries point out that the broader definition is "used only by people who are opposed to such work". The word has a negative connotation, implying torture, suffering, and death. The word "vivisection" is preferred by those opposed to this research, whereas scientists typically use the term "animal experimentation".The following text excludes as much as possible practices related to in vivo veterinary surgery, which is left to the discussion of vivisection.
History
The earliest references to animal testing are found in the writings of the Greeks in the 2nd and 4th centuries BCE. Aristotle and Erasistratus were among the first to perform experiments on living animals. Galen, a 2nd-century Roman physician, performed post-mortem dissections of pigs and goats. Avenzoar, a 12th-century Arabic physician in Moorish Spain introduced an experimental method of testing surgical procedures before applying them to human patients. Discoveries in the 18th and 19th centuries included Antoine Lavoisier's use of a guinea pig in a calorimeter to prove that respiration was a form of combustion, and Louis Pasteur's demonstration of the germ theory of disease in the 1880s using anthrax in sheep. Robert Koch used animal testing of mice and guinea pigs to discover the bacteria that cause anthrax and tuberculosis. In the 1890s, Ivan Pavlov famously used dogs to describe classical conditioning.Research using animal models has been central to most of the achievements of modern medicine. It has contributed most of the basic knowledge in fields such as human physiology and biochemistry, and has played significant roles in fields such as neuroscience and infectious disease. For example, the results have included the near-eradication of polio and the development of organ transplantation, and have benefited both humans and animals. From 1910 to 1927, Thomas Hunt Morgan's work with the fruit fly Drosophila melanogaster identified chromosomes as the vector of inheritance for genes. Drosophila became one of the first, and for some time the most widely used, model organisms, and Eric Kandel wrote that Morgan's discoveries "helped transform biology into an experimental science". D. melanogaster remains one of the most widely used eukaryotic model organisms. During the same time period, studies on mouse genetics in the laboratory of William Ernest Castle in collaboration with Abbie Lathrop led to generation of the DBA inbred mouse strain and the systematic generation of other inbred strains. The mouse has since been used extensively as a model organism and is associated with many important biological discoveries of the 20th and 21st centuries.
In the late 19th century, Emil von Behring isolated the diphtheria toxin and demonstrated its effects in guinea pigs. He went on to develop an antitoxin against diphtheria in animals and then in humans, which resulted in the modern methods of immunization and largely ended diphtheria as a threatening disease. The diphtheria antitoxin is famously commemorated in the Iditarod race, which is modeled after the delivery of antitoxin in the 1925 serum run to Nome. The success of animal studies in producing the diphtheria antitoxin has also been attributed as a cause for the decline of the early 20th-century opposition to animal research in the United States.
Subsequent research in model organisms led to further medical advances, such as Frederick Banting's research in dogs, which determined that the isolates of pancreatic secretion could be used to treat dogs with diabetes. This led to the 1922 discovery of insulin and its use in treating diabetes, which had previously meant death. John Cade's research in guinea pigs discovered the anticonvulsant properties of lithium salts, which revolutionized the treatment of bipolar disorder, replacing the previous treatments of lobotomy or electroconvulsive therapy. Modern general anaesthetics, such as halothane and related compounds, were also developed through studies on model organisms, and are necessary for modern, complex surgical operations.
In the 1940s, Jonas Salk used rhesus monkey studies to isolate the most virulent forms of the polio virus, which led to his invention of the polio vaccine. The vaccine, which was made publicly available in 1955, reduced the incidence of polio 15-fold in the United States over the following five years. Albert Sabin improved the vaccine by passing the polio virus through animal hosts, including monkeys; the Sabin vaccine was produced for mass consumption in 1963, and had virtually eradicated polio in the United States by 1965. It has been estimated that developing and producing the vaccines required the use of 100,000 rhesus monkeys, with 65 doses of vaccine produced from each monkey. Sabin wrote in 1992, "Without the use of animals and human beings, it would have been impossible to acquire the important knowledge needed to prevent much suffering and premature death not only among humans, but also among animals."
On 3 November 1957, a Soviet 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 an enormous step forward in 1974 when Rudolf Jaenisch could produce the first transgenic mammal, by integrating DNA from simians 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.
Other 20th-century medical advances and treatments that relied on research performed in animals include organ transplant techniques, the heart-lung machine, antibiotics, and the whooping cough vaccine. Treatments for animal diseases have also been developed, including for rabies, anthrax, glanders, feline immunodeficiency virus, tuberculosis, Texas cattle fever, classical swine fever, heartworm, and other parasitic infections. Animal experimentation continues to be required for biomedical research, and is used with the aim of solving medical problems such as Alzheimer's disease, AIDS, multiple sclerosis, spinal cord injury, many headaches, and other conditions in which there is no useful in vitro model system available.
Toxicology testing became important in the 20th century. In the 19th century, laws regulating drugs were more relaxed. For example, in the US, the government could only ban a drug after they had prosecuted a company for selling products that harmed customers. However, in response to the Elixir Sulfanilamide disaster of 1937 in which the eponymous drug killed over 100 users, the US 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.