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Abuse of Antibiotics at Factory Farms Threatens the Effectiveness of Drugs Used to Treat Disease in Humans

Routine, medically unnecessary use of antibiotics to promote more rapid growth of livestock is making disease-causing bacteria more resistant to the drugs, diminishing the drugs' power to treat life-threatening diseases in humans.

For centuries, infections caused by bacteria were a major source of disease and death from illnesses such as pneumonia and tuberculosis. The discovery of antibiotics has proven critical in greatly reducing infectious diseases, and protecting public health relies heavily on the use of antibiotics. But repeated exposure to the drugs enables resistant strains of bacteria to evolve. Some bacteria are naturally resistant, so they survive treatment and multiply. When antibiotics are given again the resistant bacteria survive, and as their proportion of the bacterial population increases over time, the drugs become less effective. The more antibiotics we use, the more likely it is that bacteria will become resistant. The Institute of Medicine, part of the National Academy of Sciences, estimated that the annual cost of treating antibiotic-resistant infections in the U.S. is $30 billion. (National Institute of Allergy and Infectious Diseases)

The increased use of antibiotics in animal production has gone hand-in-hand with the development of industrial-style livestock operations. With thousands of animals crammed into the unhygienic, crowded quarters of a typical factory operation, antibiotics are dispensed constantly through the animals' feed. Fifty million pounds of antibiotics are produced in the U.S. every year; 40% of that is given to animals, and 80% of what is given to animals is used to promote their growth. (American Medical News, 1999) Scientists do not understand how or why the drugs promote growth. Many of the same antibiotics -- six of the 17 classes of antibiotics -- used to promote growth in animals are also used to treat diseases in humans. (The New York Times, 1999)

Evidence is increasing that the emergence of antibiotic resistance, caused by overuse of antibiotics, threatens public health.

Drug-resistant infections, some fatal, have been increasing in people in the U.S. Many scientists attribute the problem to the misuse of antibiotics in humans and animals. (The New York Times, 1999) Although it is not the only source of the problem, the use of antibiotics to promote livestock growth is a major contributor to antibiotic resistance.

In more than one-third of the salmonella-poisoning cases in 1997, the bacteria were resistant to five antibiotics used to treat the disease, according to the Centers for Disease Control and Prevention. Drug resistance in campylobacter bacteria, the most common known cause of bacterial food borne illness in the United States, increased from zero in 1991 to 14 percent in 1998. (The New York Times, 1999)
A Harvard University study showed that antibiotic-resistance genes found in bacteria infecting humans were identical to some of the same bacteria infecting animals. (O'Brien et.al., 1982) Scientists at the Centers for Disease Control linked an outbreak of antibiotic-resistant salmonella in humans to beef cattle that had been fed subtherapeutic doses of chlortetracycline for growth promotion. (Holmberg, et.al., 1984)

Staph bacteria, which cause skin, blood, heart valve, and bone infections that can lead to septic shock and death, are becoming increasingly resistant to the chief antibiotic that has been used to treat staph infections, methicillin. From 1975 to 1991, incidence of methicillin-resistant staph bacteria in U.S. hospitals has increased from 2.4 percent to 29 percent. Staph infections are increasingly becoming resistant to the last line of defense, vancomycin. (Panlilio, 1992)

The European Union, on the recommendation of the World Health Organization, has banned the use of antibiotics to promote the growth of livestock animals when those drugs are also used to treat people. The U.S. Center For Disease Control and Prevention has agreed with this position, but the U.S. government has thus far failed to act to reduce the threat to human health of ineffective antibiotics. (Lieberman, et.al., 1999)

To reduce the health threats posed by increasing antibiotic resistance, the Food and Drug Administration should ban the use of antibiotics to promote livestock growth when those antibiotics are used to treat humans.

For more information about the Sierra Club's opposition to factory livestock production, contact your local Sierra Club Chapter.

Another Sierra Club Fact Sheet on Antibiotics and CAFOs

The Washington Post, A Look At...Antibiotics in the Food Chain

Sources:

American Medical News, "FDA Pledges to Fight Overuse of Antibiotics in Animals" February 15, 1999.

Holmberg, S.D., Osterholm, M.T., Senger, K.A., and Cohen, M.L., "Drug-resistant Salmonella from animals fed antimicrobials." New England Journal of Medicine 1984; 311:617-622.

Lieberman, Patricia, et.al., "Protecting the Crown Jewels of Medicine. A Strategic Plan to Preserve the Effectiveness of Antibiotics," Center for Science in the Public Interest, 1999.

The New York Times, "A Move to Limit Antibiotic Use In Animal Feed. Fewer Hardy Bacteria in People is U.S. Goal." March 8, 1999.

O'Brien, T.F., Hopkins, J.D., Gilleece, E.S., Mederios, A.A., Kent, R.L., Blackburn, .O., Holmes, M.B., Reardon, J.P., Vregeront, J.M., Schell, W.L., Christenson, E., Bissett, M.L., and Morse, E.V., Molecular epidemiology of antibiotic resistance in salmonella from animals and human beings in the United States, New England Journal of Medicine 1982; 307: 1-6.

National Institute of Allergy and Infectious Diseses, "Antimicrobial Resistance Fact Sheet," http://www.niaid.nih.gov/factsheets/antimicro.htm . March, 1999.

Panlilio, A.L., "Methicillin-resistant Staphylococcus aureus in U.S. Hospitals, 1975-1991, Infection Control Epidemiology," 1992; 1