The Debate over Animal Experiments
The conflict over the practical and ethical problems presented by animal experiments was the subject of a series of articles in the February issue of Scientific American. The case against animal experiments was made by PCRM president Neal Barnard, M.D., and Stephen R. Kaufman, M.D., of the Medical Research Modernization Committee. Animal experiments, they wrote, are poorly suited to addressing the pressing health problems of our era, particularly heart disease, cancer, stroke, AIDS, and birth defects. Other research methods are much more effective.
The value of nonanimal research methods is shown in the example of heart disease. First, human population studies, such as the Framingham Heart Study, revealed risk factors, including high cholesterol levels, smoking, and high blood pressure. Then, researchers conducted clinical intervention trials in which these risk factors were altered and the resulting decrease in heart disease was shown. Autopsy results and chemical studies added further links between risk factors and disease, showing, for example, that people on high-fat diets develop artery blockages early in life. While some experimenters have fed fatty diets to animals, attempting to recreate human findings, such studies did not add to what was already known from human clinical research.
In AIDS research, human population studies showed how the disease is transmitted, permitting prevention programs to begin. Test-tube studies using human cells and serum allowed researchers to identify the AIDS virus and study how it causes disease. Other test-tube studies have been used to check the efficacy and safety of important new AIDS drugs such as AZT, 3TC, and protease inhibitors.
In birth defects, animal tests have proven to be embarrassingly poor predictors of what can happen in humans. Again, human population studies and clinical intervention trials showed a much more effective approach. Epidemiologic surveys showed the link between neural tube defects and folate deficiency, and allowed the identification of fetal alcohol syndrome. Clinical studies showed how magnesium sulfate could potentially prevent cerebral palsy and mental retardation in very low-birth-weight babies in 63 percent and 49 percent of cases, respectively. More birth defect research is needed, and every dollar that goes to experiments on rats and mice is a dollar that is not available for studies that could track down the causes of human birth defects.
Observations of humans have proved to be invaluable in cancer research as well. Studies at the State University of New York at Buffalo and elsewhere have shown that cancer patients who follow certain kinds of diets—particularly diets low in fat and rich in vegetables and fruits—live longer and have a lower risk of recurrence. Predicated on these findings, we now need intervention trials to test which specific diets help people with various types of cancers.
Animal experiments have often delayed important advances. For example, researchers at the Mayo Clinic reported that of 25 compounds shown to reduce damage from strokes in animal experiments, none worked in human patients. In the 1920s and 1930s, studies on monkeys led to gross misconceptions that delayed the fight against polio. These experiments indicated that the poliovirus infects mainly the nervous system; scientists later learned this was because the viral strains they had administered, via the nose, had developed an unusual affinity for brain tissue as a result of their passage through animals.
Tobacco inhalation experiments on animals strongly indicated that tobacco did not cause lung cancer. Tobacco tar painted on animals’ skin did cause tumors to develop, but these results were deemed less relevant than the inhalation studies. The tobacco lobby and its scientific advisors were able to use the animal experiments to delay government warnings. Human population research clearly showed the tobacco-cancer connection, and recent human DNA studies have identified tobacco’s “smoking gun,” showing how a derivative of a tobacco carcinogen actually targets human genes, causing cancer.
Although human population studies, clinical intervention trials, and cellular studies will remain the foundation of research, they are not the only methods with advantages over animal tests. Noninvasive imaging techniques allow researchers to look inside the human body as never before. Functional magnetic resonance imaging can map brain activity with a resolution of less than 1.4 millimeters. Positron emission tomography can also identify brain regions involved in specific memories and other brain functions. New non-animal tests have proven to be more accurate than animal tests at predicting the safety of chemicals and are also used to design and test new drugs.
Many behaviorists have come to a new appreciation of the tremendous complexity of animals’ lives, including their ability to communicate, as well as of their social structures and emotional repertoires, making it impossible to regard animals as mere laboratory supplies. However, pragmatic issues alone should encourage scientists and governments to put research money elsewhere.