Antibiotics in animal agriculture

2017-11-09

This year, ReAct focuses it’s efforts during the World Antibiotic Awareness Week on antibiotic use in food production. Food production has always been an important issue for mankind, and the current food industry is relying on antibiotics to secure the supply of food and income to farmers. However, the use of antibiotics for food production has been a major driver of antibiotic resistance, which is emerging as a threat to food security.

Scale of Antimicrobial Use

The amount of antibiotics used in agriculture globally is not known as much of the use is unregulated, but the amount used for food production is significantly higher than the use in humans. Most of the agricultural use is in animal production, although a small part is used in plant culture. As an example, estimates of antibiotic use in the United States state that 70-80% of antibiotics are sold for use in animals. With the increase in human population and increased demand of meat, the OECD estimates that antibiotic use in food animals will increase by 67% globally from 2010 to 2030 if nothing is done.

Why are antimicrobials used in animal farming?

Treatment of disease

Animals do fall ill, just as humans do. If the disease is caused by bacteria, the animals need antibiotics. However, some estimates claim that only 10% of the antibiotic use in animal husbandry is for treatment of disease.

Prevention of disease

The use of antibiotics for prevention of disease can be subdivided into prophylaxis and metaphylaxis. Common for both of these uses is that the animals that receive the antibiotics are not infected, but are under risk of contracting an infection for a variety of reasons.

Growth promotion

Some early studies showed that by routinely giving animals subtherapeutic doses of antibiotics, the animals grew faster, thus increasing the yield from animal production. Unfortunately, warnings of antibiotic resistance were ignored.

Alternatives to antibiotics

Often proponents of liberal antibiotic use in agriculture state that they are necessary for good animal husbandry. However, antibiotic use for growth promotion has been banned in several countries with little or no consequences on animal welfare or productivity. Practices including infection prevention measures appear sufficient to maintain food security.

Why is this important?

The antibiotics used in animals are either the same or similar to the antibiotics used in human medicine. As antibiotic use selects for resistance in bacteria, overuse in animals increases resistance levels in bacteria in the animal’s environment, including in the farmers. These resistant pathogens or genes can then spread throughout the community via humans, manure, or the animals via abattoirs.

One scary example is the use of colistin in pig farming. Colistin was used in human medicine between the 1950s and 1970s, after which its use diminished as safer drugs were developed. It was however not completely abandoned, and with increasing rates of multidrug resistance, colistin was revived and recognized as a critically important antibiotic to be used as a last resort to be used when all other therapies failed. Meanwhile, colistin was marketed to farmers as an efficient food additive with no risk for resistance development. Unfortunately, colistin use in agriculture lead to selection of resistance, and when the mcr-1 gene was discovered the disaster became apparent. mcr-1 provides colistin resistance and is located on a plasmid, a mobile genetic element. This makes it transferrable between different strains and even species of bacteria. Now, mcr-1 has been found worldwide in the environment, animals and humans – even causing disease in patients. Colistin resistance has also been found together with other types of resistance elements, causing infections that do not respond to antibiotic therapy.

Need for action

To curb the development of resistance in animal agriculture, measures need to be taken to reduce the use of antibiotics. Such measures include:

Stop using antibiotics for growth promotion.
Minimize antibiotic use for prevention of infection.
Implement infection prevention measures, including vaccines, to reduce disease.

Antibiotic resistance in animal agriculture is not only threatening animal health, but also affects human health. To learn more about the problem and how to take action, visit the Toolbox for more information.

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