Do Antimicrobial Mass Medications Work?

By Sarah MooreReviewed by Sophia Coveney

The global human population is growing exponentially, increasing the need for housing, which is putting agricultural land under competition. Additionally, the rising number of people is putting an increased demand for limited food sources. As a result, farmers are feeling pressured to produce more food out of smaller spaces.

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One solution is to tackle disease in livestock, which would reduce the number of deaths due to illness and produce more viable meat and poultry. Antimicrobial medication use has been steadily rising in agriculture, however, its efficacy at preventing illness is being questioned, and scientists are warning of its indirect detrimental impact on humans.

Around the world, roughly 700,000 people die each year due to antimicrobial resistance, and this is expected to rise to 10 million by 2050. Human antimicrobial resistance has been linked, at least in part, to the consumption of meat and poultry that has been treated with antimicrobial mass medications.

Given the controversy over the efficacy of antimicrobial mass medications, and their link with human antimicrobial resistance, proper investigation and measurement of the impact of antimicrobial mass medications on livestock is vital.

Increasing the use of antibiotics to meet rising demand for meat

Concern is growing over increasing antimicrobial resistance in livestock. Each year, around 200 million tons of meat is produced for human consumption. However, due to the growing global population, meat production is set to rise to around 470 million tons by 2050. For this reason, it is expected that antimicrobial medications will become more heavily relied upon by the agricultural industry to manage disease and boost meat production.

Recent studies have explored the efficacy of such medications at promoting antimicrobial prophylaxis (preventing against the establishment of a specific disease) and metaphylaxis (preventing the spread of infectious disease by treating a group of animals after diagnosis of disease in one or several members) in livestock.

Efficacy of antimicrobial mass medications at controlling for animal disease

In 2017, a team in Denmark conducted a systematic review and meta-analysis of randomized controlled clinical trials investigating the efficacy of antimicrobial mass medications in preventing Bovine respiratory disease (BRD).

Results revealed that antimicrobial prophylaxis and metaphylaxis were not reliably correlated with a reduced risk of death from BRD. Data showed that the associated risk reductions were highly variable and were dependent on the classes of antimicrobial medications used as well as BRD attack rates and duration of the clinical trial. Broad-spectrum antimicrobial combination medications were associated with the greatest risk reductions, however, the results reflect only short-term gains and do not take into account the long-term or indirect implications of mass antimicrobial medication use.

Other studies have further undermined the efficacy of antimicrobial mass medications. It appears that, despite the widespread use of such medications over recent decades, infection rates have not been controlled as much as they should have been, suggesting limitations in the use of antimicrobial medications. Rates of BRD, in particular, have failed to show significant reductions in the last 10-20 years. While around a third of animals received antimicrobials, rates of BRD mortality rose between 1994 and 2011 from 1.03% to 1.6%, suggesting the inefficacy of antimicrobial medications against BRD.

Other studies have demonstrated that antimicrobial mass medications have the impact of reducing morbidity, but that this effect is limited, and antimicrobial medications certainly cannot eradicate infection and death.

Experts believe that other approaches to reducing disease and death in livestock should also be considered alongside antimicrobial mass medications, such as cleaning and disinfecting protective clothing and vehicles, improved education on the symptoms of disease for early detection, and vaccination.

The data shows that the efficacy of antimicrobial mass medications is limited, and further measures need to be taken to reduce infection and death of livestock. The development of new approaches to disease prevention, diagnosis, and treatment is also vital to reducing the reliance on antimicrobial medications, protecting humans from the negative indirect effects of consuming meat and poultry that have been treated with these medications.

Antimicrobial resistance in humans linked to meat and poultry consumption

A growing body of evidence is strengthening the link between human antimicrobial resistance and resistant microbes that are suspected to have originated in livestock, and transmitted to humans through the consumption of meat and poultry.

Numerous studies have shown that as the use of antimicrobial medicine reduces in a particular region, as does the prevalence of human antimicrobial resistance. For example, following the ban of glycopeptide avoparcin across the EU in the 1990s, vanco­mycin-resistant enterococci resistance in both humans and poultry became less common.

This data should be taken into consideration by the agricultural sector in making strategies for the future of meat and poultry production, especially as farmers will be feeling the pressure to increase production levels to meet rising demand. Developing sustainable strategies that have minimal negative implications is essential for promoting future food security and meeting the world’s rising food demands.

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