Antibiotic Overuse in Livestock: A Looming Public Health Crisis

Issue 13, Volume 113

By Ryan Lin 

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You wake up and find that your throat is extremely sore. You take a sip of water, but even swallowing is painful. These are common symptoms of strep throat, a bacterial infection contracted by millions each year.

Every year, healthcare professionals prescribe antibiotics to treat bacterial infections in over 200 million people in the United States alone. From mild strep throat to bacterial pneumonia, many bacterial infections can be easily treated with a simple regimen of antibiotics, such as penicillin or tetracycline. However, if these antibiotics lost their effectiveness, common illnesses like strep throat could quickly develop into severe rheumatic fever or kidney inflammation. Surprisingly, 80 percent of the antibiotics sold in the United States each year are used on food-producing animals, not humans. The use of antibiotics in the livestock industry has heavily contributed to the development of antibiotic-resistant bacteria.

Antibiotics are used on livestock for four main purposes: treating sick animals, protecting healthy animals, preventing disease, and promoting growth. The widespread use of antibiotics in livestock—such as chickens, pigs, and cows—can be attributed to the agricultural industry’s economic motives. Though factory farms’ massive livestock populations often lead to crowded and unsanitary conditions, they primarily use antibiotics to induce growth and increase the productivity of animals rather than to specifically target diseases that inevitably emerge. These antibiotics inhibit microbe growth in the gastrointestinal tract, triggering the immune system to promote efficient growth.

With the large-scale use of antibiotics on livestock, these lifesaving drugs are becoming less effective for people. The World Health Organization (WHO) reported that treatable diseases like sepsis, urinary tract infections, and tuberculosis have become harder to treat over time . Understanding this phenomenon requires an analysis of bacterial evolution. When bacteria undergo binary fission––the process which carries out cell division––errors can occur in the copying of DNA. These errors are known as mutations, which are common among rapidly-dividing bacteria. While some mutations are harmful to bacteria, others can provide them with advantages such as antibiotic resistance. Those with beneficial mutations survive the antibiotic and continue to multiply, creating diseases that we can no longer treat. For example, bacteria such as Staphylococcus aureus and Neisseria gonorrhoeae, which cause gonorrhea, are now almost always resistant to the antibiotic benzyl penicillin. Resistance to this accessible antibiotic is especially concerning, as it narrows down treatment options for patients. Despite these concerns, antibiotics are continually used on livestock, creating a positive feedback loop that further increases bacterial resistance.

According to Robert Lawrence, an emeritus professor of environmental health at Johns Hopkins University, using low-dose antibiotics on animals in factory farms sets up the perfect conditions for spontaneous mutations in bacterial DNA. With more spontaneous mutations, the chance of the emergence of an antibiotic-resistant trait increases. Resistant bacteria can become strains that quickly spread between livestock in the crowded conditions of factory farms and impact food sources internationally.

In addition to these risks, antibiotic use in factory farming could lead to an untreatable bacteria pandemic among humans, as bacterial outbreaks can spread to people, causing serious infections. Normally, doctors prescribe antibiotics to treat such infections, but this practice is deemed ineffective when the bacteria have developed resistance.

Antibiotic use in livestock has also led to concerns about harmful residues in food products. These antibiotic residues can cause allergic reactions and digestive problems in humans. To prevent these issues, the U.S. Food and Drug Administration (FDA) has established minimum intervals between the last dosage of antibiotics and the slaughter of the animal. Antibiotic residues can also be found in the milk of dairy cows, which can only be reduced after a withdrawal period that lasts around nine days; boiling the milk does not get rid of the antibiotic residues. Physicochemical analyses are mandated to ensure that the antibiotics do not exceed the maximum residue limit before the product is put on the market. Drug and antibiotic residues above the maximum level in food are recognized as illegal by various public health authorities, including the United States Department of Agriculture and the WHO.

Only in the 2010s did the FDA mandate veterinary prescriptions for antibiotics and ban the use of antibiotics in production. Consequently, from 2015 to 2017, sales of medically important antibiotics for livestock plummeted by 42 percent. Medically important antibiotics are defined by the WHO as critical to human medical treatment.

The WHO continues to combat the overuse of antibiotics in livestock to preserve their effectiveness in human health. Antibiotics used on livestock should be selected from those the WHO lists as “least important” to human health rather than those classified as critical to human treatment. This prevents bacteria from becoming resistant to antibiotics that are commonly used to treat patients. Despite the ban, the conditions of factory farms make antibiotics a necessity to counteract the severe health implications livestock face. In response to these concerns, the European Union deemed the use of antibiotics for the purpose of poor hygiene and unsanitary conditions on these farms illegal.

Despite the harm of their overuse, the complete elimination of antibiotics in the livestock industry would not be beneficial. Outside of growth purposes, it would be inhumane to allow animals to suffer from contracted diseases. Additionally, it is not economically feasible to eliminate the use of antibiotics in the livestock industry—prices would rise dramatically in response to a reduced food supply. The careful regulation of antibiotic use is critical in maintaining global health. Supporting public health advocacy groups and reducing meat consumption by shifting to a plant-based diet are ways that you, as a consumer, can help.