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SCIENCE, MEDICINE, AND ANIMALS How Have Animals Contributed to Improving Human Health? A hundred years ago, good health was much rarer than it is today. In 1870, the leading cause of death in the United States was tuberculosis. 12 Of all the people born in developed countries like the United States, a quarter were dead by the age of 25, and about half had died by the age of 50. Those fortunate enough to have survived to old age had probably experienced several bouts with diseases like typhoid fever, dysentery, or scarlet fever.13 Today, the leading causes of death in the United States are heart disease and cancer—diseases of old age rather than infancy and childhood. Fully 97 percent of Americans live past their 25th birthday, and over 90 percent live to be more than 50. Better nutrition and sanitation did much to reduce the toll from infectious diseases. But these diseases could not have been eliminated as significant causes of death and illness without animal research. Animal research has also made people healthier, since it has contributed to virtually eliminating many infectious diseases like polio or rheumatic fever that can be debilitating without causing death. Animal research has even contributed to better nutrition and sanitation, since it has helped to identify the agents that contribute to good or bad health. Because of a genetic defect, nude mice such as the one shown here have no thymus and cannot make certain cells essential for various immune responses. This characteristic makes them extremely helpful to scientists working in immunology research.
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SCIENCE, MEDICINE, AND ANIMALS Methods to combat infectious diseases have not been the only dividends of animal research. Surgical procedures, pain relievers, psychoactive drugs, medications for blood pressure, insulin, pacemakers, nutrition supplements, organ transplants, treatments for shock trauma and blood diseases—all have been developed and tested in animals before being used in humans.14 In fact, according to the American Medical Association, “Virtually every advance in medical science in the 20th century, from antibiotics and vaccines to antidepressant drugs and organ transplants, has been achieved either directly or indirectly through the use of animals in laboratory experiments.”15 Animals will continue to be essential in combatting human illness. Though human health has improved greatly over the last 100 years, much remains to be done. Many of today's leading killers, such as cancer, atherosclerosis, diabetes, Alzheimer's disease, and AIDS, remain inadequately understood. Furthermore, debilitating conditions such as traumatic injury, strokes, arthritis, and a variety of mental disorders continue to exact a severe toll on human well-being. Animal research will be no less important in the future than it has been in the past. Indeed, it may be even more important, because the questions remaining to be answered generally involve complex diseases and injuries that require whole organisms to be studied. A scientist compares similarities in baboon virus and HIV-1. This is one of the studies being conducted to help discover the proper sequence of the AIDS virus.
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SCIENCE, MEDICINE, AND ANIMALS HEART SURGERY In the nineteenth century, physicians could do very little to treat heart disease, because there was no way to repair the heart in living patients. But around the turn of the century, pioneering surgeons began to operate on the hearts of dogs and other animals, experimenting with the procedures needed to work directly on the heart. They concentrated on repairing heart valves, since damaged valves were a common consequence of rheumatic fever and other illnesses. By 1923 the procedures had advanced to the point that they were successfully used on a 12-year-old comatose girl, who lived for another 4 years before succumbing to pneumonia. Nevertheless, heart surgery remained very limited, because the heart could be stopped only for very short intervals if the patient were to survive. Some way had to be found of stopping the heart while continuing blood circulation so that more extensive repairs could be made. Consequently, researchers began working with animals in the 1930s to develop pumps that could circulate and aerate the blood. It was a complex task, requiring basic knowledge of such factors as blood clotting, transfusions, the constituents of the blood, and the effect of prolonged pumping on both the blood and the heart. But in 1953 the first operation using a heart–lung machine was performed on a human being, inaugurating the modern era of open-heart surgery. Today, heart surgery has extended and improved the lives of many people. More than 80 percent of the infants born with congenital heart defects can be treated surgically and lead normal lives. Some 3 million people undergo various kinds of cardiovascular operations and procedures in the United States each year. Without animal research, none of these techniques could have been developed.
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