Antibiotics are essential to human health. So why are we wasting them to make farm animals a tiny bit bigger?

The increasing resistance of bacteria to antibiotics is one of the most terrifying under-the-radar issues in global health. All of our superstar drugs are becoming less effective. In Southeast Asia, 98 percent of gonorrhea bacteria are now resistant to penicillin – a drug which used to work on every gonorrhea infection.  Tetracycline antibiotics are losing effectiveness across the board.


This means bacterial infections become more and more dangerous. 700,000 people die every year from infections that are resistant to antibiotics, and that number is going up, not down, faster than anyone predicted. Researchers have been scrambling to find new antibacterial drugs and identify the causes of the constant rise in resistant bacteria. A new report out of the United Kingdom points to one likely culprit: farm animals.

The UK’s Review on Antimicrobial Resistance places a substantial amount of blame on the use of antibiotics in agriculture. Excessive use of antibiotics in animal husbandry, they argue, has led to the development of resistant bacteria in fish and livestock. These resistant bacteria then spread to people through direct contact between farmworkers and animals, and when consumers eat meat. To make matters worse, the use of antibiotics in agricultural animals is expected to double between 2010 and 2030. At the same time, the report points out that these drugs actually have minimal agricultural impact. On average, the use of agricultural antibiotics improves animal growth rates by only five percent.

In other words, we are sacrificing huge gains in public health in exchange for just slightly larger farm animals.

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Good for Livestock 

The report looks at antibiotics and antifungals in livestock production (beef, swine and poultry); fish farming; and crop growing. Although data collection is very poor, the authors cite estimates that global antibiotic use in food production may range from 63,000 tons to over 240,000 tons. Even the low end estimate is massive.

Antibiotics are used in livestock to treat diseases, to prevent diseases, and to promote growth in healthy animals. In the US, animals consume twice as much antibiotics as humans do every year. These antibiotics are provided through food and water. Scientific studies suggest that 75-90 percent of antibiotics are excreted un-metabolized and enter sewage systems and water sources.

Bad for Humans

Humans and animals are affected by many of the same infections. The more antibiotics are used, the more resistance developed; it is a basic ecological fact. The first resistance to penicillin was found in 1947, only four years after the drug went on the market. The more antibiotics that are used, the more generations of bacteria evolve, and become resistant.

Using antibiotics in large quantities in animals vastly accelerates that evolution of resistance. As the report details, there are 41 antimicrobial drugs (the class that includes antibiotics) sold for veterinary use in the US. Of those, 31 are also considered important for human use. That means it is almost impossible to use antibiotics in animals without driving up the risk of resistance in humans.

One devastating example is the drug Colistin. Colistin is an old antibiotic, rarely used on people because it is dangerous to the kidneys and nervous system. However, it has unusual properties. First, because of that rare use, it was highly effective. Bacteria that have become resistant to more common, safer antibiotics, have seldom become resistant to Colistin.

Next, when bacteria did become resistant to Colistin, they didn’t share that resistance. Resistance to an antibiotic, penicillin for example, is carried on a gene. Bacteria can share genes, so when a penicillin-resistant colony of bacteria meets a non-resistant colony, the resistance gene is shared and both colonies become resistant. Colistin resistant bacteria weren’t doing that. The gene didn’t transfer.

Colistin was a valuable resource when fighting resistant bacteria.

Until November 2015. New research from China shows colistin-resistant bacteria that do share genes, found in 20% of pigs and 15% of meat sampled. One percent of (human) hospital patients also showed infection with colistin-resistant bacteria – with genes that were easily shared. What changed? Widespread use of Colistin by pig farmers in the area.

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So What Can We Do About it?

The report lays out three basic recommendations to reduce the development of resistance among bacteria.

1) Set a global target to reduce antibiotic use in agriculture. Denmark has been a leader in minimizing agricultural use of antibiotics. The report suggests taking Denmark’s level, 50mg of antibiotics per kilo of livestock or fish, as a global target. This would require a 66% reduction of antibiotic use from current levels. Justifying the target, the report points out that a reduction in antibiotic use was achieved very quickly with little reduction in productivity in The Netherlands, and that US consumers are starting to demand reductions in agricultural antibiotic use. It further states that, “Between 1992 and 2012, Denmark reduced its antibiotic consumption more than any other country in Europe, but it had the second highest growth rate in agricultural productivity, with this increasing by 65 percent, against the European average of just 25 percent in the same period.”

2) Set minimum standards to improve waste management in antimicrobial production. The problem of agricultural use of antibiotics goes beyond the animals themselves. Antibiotics and the waste of animals that have been fed antibiotics must be disposed of properly to avoid contaminating waterways. There are currently no global standards for safe disposal of farmyard antibiotics with regard to antibacterial resistance, and no environmental impact assessments on resistance that could be used to develop them. The report calls for immediate development of standards based on the best current thinking, followed by research to refine and improve those standards.

Radically improve the surveillance of antibiotic use in agriculture and antimicrobial manufacturing waste. One major theme of the report is a lack of hard data. Estimates of global agricultural antibiotic use vary by more than a hundred thousand tons. Data is missing on the disposal of waste in animals who are treated with antibiotics, and there is very little surveillance done to track the prevalence of resistant infections among livestock. The authors call for coordinated surveillance of resistant bacteria in animals and the environment, along with the impact on the health of patients.

One Possible Weakness of the Report

The UK Review on Antimicrobial Resistance is a mainstream panel, reporting to the Prime Minister. Its focus is on making effective policy, not parsing out the science of antimicrobials. This report is therefore a consensus document, intended to provide politically palatable results that can be acted on. The increase in use of agricultural antibiotics is being driven by the big pharmaceutical companies that advertise and sell the drugs. These companies also exert lobbying pressure to resist regulation of agricultural antibiotics. They also question the – obvious – science behind the spread of resistant bacteria from animals to humans in a way that is remarkably like the language used by tobacco companies when discussing cigarettes. All of this goes largely unmentioned in the report.

What you need to know about this report in just one sentence

Antibiotics are essential to human health, and we’re wasting them so we can make our farm animals a tiny bit bigger.