Tackling antibiotic resistance in agriculture

The incidence of Antimicrobial Resistance (AMR) infection-related deaths is increasing, with 33,110 being reported in 2015. That is almost twice as many as due to natural disasters and terrorism combined.

Antibiotics are victims of their own success. Since their revolutionary discovery in 1928, they have become vital not only in human medicine but also in agriculture. On farms they have been used for disease treatment and prevention and, following the announcement of their growth effect in the 1950s, growth promotion. As such, antibiotics were a significant component of the development of intensive, high volume food production. Eventually, though, their effectiveness has led to such misuse and overuse that what were once “wonder drugs” have turned ineffective.

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Over time, due to the pressure of repeated exposure to antibiotics, many microorganisms have developed resistance mechanisms to overcome their effects. Worse still these strains can distribute their resistance genes into the environment or to other organisms, essentially swapping notes on how to defend against antimicrobials.

“Antibiotics are victims of their own success. Since their revolutionary discovery in 1928, they have become vital not only in human medicine but also in agriculture”

Many of the diseases we treat animals for also occur in humans.

Almost two-thirds of human infectious diseases and three-quarters of emerging or re-emerging infectious diseases are caused by pathogens of animal origin. Notable examples of this include the historic jump of smallpox from cattle to humans, and, more recently, bird flu from Chinese poultry. With many of the antimicrobials given to animals being the same as those given to humans, or acting through similar mechanisms, our modern agricultural system is creating a perfect breeding ground for AMR pathogens which could spread to humans.

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A current concern is the emergence of zoonotic multidrug resistant brucellosis infections, which cause reproductive impairment in livestock, especially given recent reports of human to human transmission. Another is the spread of resistance against colistin – an antibiotic of last resort – from its origins on Chinese pig farms to hospital patients worldwide.

Despite these developments, the use of antibiotics is still expected to increase, with two-thirds of usage growth attributable to the production animal sector. If there are no changes in our behaviour, with a global human population set to reach 10 billion by 2050 and meat demand increasing by 50-70 percent over the same period, we will have a worsening AMR situation on our hands.

Yet, though the prospects are alarming, a few interventions can improve the situation.

The first call of action is to reduce antibiotic use in farming and the quantities dispersed into the environment. Antibiotic use has been decreasing in the EU, with a 12 percent reduction from 2011 to 2014 and a 22 percent reduction in the UK over the same period. This has been driven partially by both national and international policy and awareness programmes. The European parliament has also introduced a range of restrictions, effective from 2022, prohibiting the use of antibiotics for animal prophylaxis or growth enhancement.

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“In perspective, the cost of developing a new diagnostic approach is marginal when compared to the enormous potential gains. It is actually the cost of inaction that is too great a price to pay.”

However, real success can only be achieved through taking a multifactorial approach. The Hippocratic oath, historically sworn by doctors, states that “prevention is preferable to [a] cure” and this principle should be applied in livestock farming. Good hygiene, greater use of vaccines and better animal husbandry practices are essential to preventing disease spread between farms. Sick animals should be quickly and adequately isolated from their herds, and rapid diagnostic tests can enable the most effective treatment to be started as soon as possible.

The development of rapid diagnostics is one of the key pillars emphasised in O’Neill’s AMR review. Many animal diseases typically take a week to diagnose using current processes of laboratory testing. That is a week during which infected animals can spread the disease throughout the herd and may succumb to infection.

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Rapid diagnostics will transform the way animal diseases are handled on the farm by enabling faster decision making and better antibiotic selection. Not only will this cut down the time and cost of dealing with a disease, it will also lead to a more targeted treatment, improve animal welfare and prevent opportunities for an infection to spread, which will itself reduce the need for further antibiotic treatments.

Advances in biotechnology are enabling rapid diagnostic methods to help tailor our antimicrobial drug use to specific infections. By directly and specifically detecting the DNA or RNA of infective agents to quickly discern if the disease is viral, bacterial, or fungal in origin, they allow the correct respective antibiotic, antiviral or antifungal agent to be prescribed. Furthermore, the specific strain of a pathogen and its resistance to certain treatments can potentially also be detected. This allows animals to be treated with the drugs most likely to cure their infection and least likely to cause resistance in humans, while simultaneously reducing the indiscriminate use of broad-spectrum antibiotics.

Smarter medicine and agriculture can enable more profitable farms, healthier animals, and a healthier society. In perspective, the cost of developing a new diagnostic approach is marginal when compared to the enormous potential gains. It is actually the cost of inaction that is too great a price to pay.

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Lina Gasiūnaitė is Co-founder and Director of Science at Biotangents, a veterinary diagnostics company based in Scotland, developing pen-side tests for infectious diseases of livestock.

This article first appeared in the Longitude Prize Blog.

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