It is estimated that over 100 million animals are used every year worldwide in the multibillion-dollar research industry that includes university, pharmaceutical and diagnostic laboratories, and many others. Although this number is unverifiable in the U.S., due to Animal Welfare Act (AWA) exclusions. The NIH, within the Department of Health and Human Services, spends an estimated $5.5 billion annually to support animal research. In addition to the use of animals in education and the testing of chemicals, household products, personal care products and cosmetics, animals are also commonly used in biomedical research.
Biomedical research describes a broad area of research that comprises studies of the detection, cause and treatment of both mental and physical diseases and conditions, as well as studies of the processes affecting disease and human well-being. Animals are often used as models of human disease in studies designed to understand the underlying mechanisms, causes, and treatment of diseases.
Researchers can manipulate animals in many ways to induce disease-like symptoms, and then test the effects of different treatments. Many of these experiments cause the animals a great deal of pain and distress. Ultimately, most animals are killed after the experiment ends or may die from the experimental procedure itself.
Some examples of the ways that animals are used to model human diseases in the laboratory include:
- Animals can be genetically manipulated or implanted with tumors to serve as cancer models, which significantly impacts the health of those animals and their well-being. Such treatments can impair the animals’ ability to move, breathe and eat, and ultimately these animals are killed at the end of the procedure.
- Animals can be genetically modified to express human genes implicated in conditions such as Alzheimer’s disease. In some instances, these animals are subjected to a passive avoidance task to evaluate learning and memory where they learn to avoid an environment in which they had previously received an electrical shock. In other circumstances, these impaired animals may be challenged to swim in pools to see if they can remember the placement of an elevated platform, in an effort to test their learning and memory.
- Some animals, typically rodents, are genetically modified or are fed extra high-fat diets to mimic conditions of obesity, including weight gain and onset of diabetes.
- Stroke research also utilizes animal models. Here, animals undergo surgery to induce blood-flow blockage in their brains in an effort to imitate what happens in a human stroke. This procedure alone can cause animals to die, but if they survive, they are left severely impaired and are subjected to additional testing to check for various deficits. For example, they may be placed on elevated spinning devices, akin to a rolling log, to test their balance and coordination. These are devices from which they may fall if they had sustained injuries from their experiment. Despite numerous attempts to find new stroke treatments, those that show promise in animal models have not shown promise in human treatments or cures.
- Animals are used as models of substance abuse and addiction. They are exposed to alcohol, nicotine, opiates and cocaine in an effort to understand the neurobiological basis of drug addiction, including drug craving, physical dependence, and conditions that may affect the possibility of relapse.
- Animals are also used to test the safety and efficacy of drugs during the drug development process. By the end of the process, mice, rats, pigs, dogs, monkeys and other animals may have been used. Although many drugs may appear to be safe and effective in animal models, oftentimes, this does not translate to successful human clinical trials. Despite the time (approximately 13 years) and cost ($1 billion) to develop a new drug, over 90% of drugs that make it to human clinical trials—because of promising preclinical studies—fail in human clinical trials due to issues with safety or efficacy.
Although the FDA Modernization Act 2.0 was signed into law in 2022 and aims to modernize drug development and testing by allowing alternatives to traditional animal testing, challenges remain in its implementation, including concerns about the readiness and reliability of non-animal testing methods and potential biases in regulatory decisions.
Limitations of animal models are well documented, and reproducibility issues with animal experiments remain an ongoing issue for the scientific community. Many landmark studies using animals have not been able to be reproduced; yet clinical trials and follow-up publications have been based on this irreproducible data, putting people at risk and wasting animal lives.
