Historical Impact of Animal Experimentation

Proponents of animal experimentation (tests, experiments and "educational" exercises involving harm to animals) claim that it has played a crucial role in virtually all medical advances.5,6 However, several medical historians argue that key discoveries in such areas as heart disease, cancer, immunology, anesthesia and psychiatry were in fact achieved through clinical research, observation of patients and human autopsy.7-16

Human data has historically been interpreted in light of laboratory data derived from nonhuman animals. This has resulted in unfortunate medical consequences. For instance, by 1963 prospective and retrospective studies of human patients had already shown a strong correlation between cigarette smoking and lung cancer.17,18 In contrast, almost all experimental efforts to produce lung cancer in animals had failed. As a result, Clarence Little, a leading cancer animal experimenter, wrote: "The failure of many investigators to induce experimental cancers, except in a handful of cases, during fifty years of trying, casts serious doubt on the validity of the cigarette-lung cancer theory."19 Because the human and animal data failed to agree, this researcher and others distrusted the more reliable human data. As a result, health warnings were delayed for years, while thousands of people died of lung cancer.

By the early 1940s, human clinical investigation strongly indicated that asbestos causes cancer. However, animal studies repeatedly failed to demonstrate this, and proper workplace precautions were not instituted in the U.S. until decades later.20 Similarly, human population studies have shown a clear risk from exposure to low-level ionizing radiation from diagnostic X-rays and nuclear wastes,21-24 but contradictory animal studies have stalled proper warnings and regulations.25 Likewise, while the connection between alcohol consumption and cirrhosis is indisputable in humans, repeated efforts to produce cirrhosis by excessive alcohol ingestion have failed in all nonhuman animals except baboons, and even the baboon data is inconsistent.26

Many other important medical advances have been delayed because of misleading information derived from animal "models". The animal model of polio, for example, resulted in a misunderstanding of the mechanism of infection. Studies on monkeys falsely indicated that the polio virus was transmitted via a respiratory, rather than a digestive route.27,28 This erroneous assumption resulted in misdirected preventive measures and delayed the development of tissue culture methodologies critical to the discovery of a vaccine.29,30 While monkey cell cultures were later used for vaccine production, it was research with human cell cultures which first showed that the polio virus could be cultivated on non-neural tissue.31 Similarly, development of surgery to replace clogged arteries with the patient's own veins was impeded by dog experiments which falsely indicated that veins could not be used.32 Likewise, kidney transplants, quickly rejected in healthy dogs, were accepted for a much longer time in human patients.33 We now know that kidney failure suppresses the immune system, which increases tolerance of foreign tissues.

Nevertheless, society continues to support animal experimentation, primarily because many people believe that it has been vital for most medical advances.34 However, few question whether such research has been necessary or even beneficial to medical progress.

 

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