Brief History of Animal Testing in the United States

Written By Saachi Jain

Over 110 million animals die annually during laboratory testing in the United States. Despite its ethical concerns, however, animal testing continues to be instrumental in the development of medical treatments to prevent harmful side effects such as infertility, birth defects, liver damage, and more.

Initial use and regulation of animal testing

Animal experimentation dates back to 200 CE, when Galen, a Greek physician, dissected animals to compare human anatomy. Ibn Zuhr, an Arab physician in the 12th century, was the first scientist to practice surgical procedures on animals before performing them on humans. Around the same time period, other scientists performed exploratory dissections called vivisections on animals to learn about nerves, tendons, and organ systems.

In the early 1910s, American scientist Simon Flexner injected the polio virus directly into the spines of rhesus monkeys in an attempt to create a polio vaccine. The virus replicated at high levels throughout the monkey's nervous system while avoiding the bloodstream, leading him to conclude that the virus spread directly to the brain. However, other scientists quickly discovered that the same conclusion could not be drawn with humans, and the creation of a vaccine was delayed by almost 40 years due to his assumption.

Until the 1930s, the 1906 Pure Food and Drug Act was the only regulatory measure on the production of drugs and vaccines in the US. The low restrictions permitted the wide use of an antibiotic called sulfanilamide in 1937 which had gone through limited testing and resulted in over 100 deaths before being retracted. These deaths led to the 1938 Food, Drug, and Cosmetic Act, which mandated that drugs go through an animal testing stage before being administered to humans.

In 1966, the Animal Welfare Act (AWA) marked a significant milestone in the advancement of animal welfare policies. This act was created in response to allegations from pet owners that pets were being sold as test subjects. Since its initial passage, it has been amended eight times, mostly to expand the range of species protected. The AWA defines the standard of care for laboratory animals and establishes committees to enforce and inspect the procedures of authorized organizations. 

Modern landmarks of animal testing in the United States

Animal testing has been further refined in recent decades and has paved the way for many scientific advancements. In the 1970s, researchers induced leukemia in mice to learn about the disease’s mechanisms. They discovered that all malignant cells must be destroyed to fully cure the animal of cancer. The study also showed that earlier treatment of the cancer increases the likelihood of success. 

In 2010, researchers discovered that mice with cystic fibrosis were better at regulating the pH of their airway surface liquid—a thin layer of liquid between airway tissues and gas—compared to pigs and humans with the same condition. Researchers then isolated an enzyme present in mice but lacking in pigs. Given the similar manifestations of cystic fibrosis in pigs and humans, research has begun to leverage this enzyme as a potential treatment method in humans.

Policy regarding animal testing and animal use requirements has also been subject to recent change. In December of 2022, President Joe Biden signed the FDA Modernization Act 2.0 into law, allowing drugs to skip the in-vivo testing stage and proceed directly to human trials. However, the act does not outlaw the practice, giving manufacturers the discretion to decide if animal testing would be beneficial. The signing of this law was a landmark achievement for animal advocates nationwide, who have continuously argued that animal testing is ineffective and expensive. 

Largely aided by legislation that enforces more humane practices and procedures, the use of animals in research greatly evolved in the past few centuries. There have been countless successes, but many opportunities for refinement in animal testing policy still remain to minimize harm while allowing science to flourish.

Saachi Jain
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