Antimicrobial Use in Food Animals and Emergence of Drug Resistant Microbes: A Ticking Time-Bomb

Use of antimicrobials in livestock, especially to maintain health and promote growth, has been an under-appreciated issue. Estimates peg upto 80% of the America’s national antimicrobial consumption to their use in livestock. (1) The problem is expected to be of far greater intensity in countries which have a poorly regulated pharmaceutical sector, and where there is possibility of procuring antimicrobials as over-the-counter medicines.

In India, this situation is uniquely complicated by the presence of a large group of non-formal healthcare providers, who often issue unwarranted prescriptions for antimicrobials for use in the veterinary sector.

Problems with Antimicrobial abuse

The issue with antimicrobial overuse or abuse is that it contributes to the emergence of antimicrobial resistance in bacteria. This is applicable to antimicrobial abuse, be it in the human or animal health sector. In the animal sector, these drugs are often used for prolonged periods, in subclinical doses, which favours the selection pressure by which the resistant strains of bacteria tend to thrive. Additionally, there is always the risk that these bacteria maybe transmitted to man through food products or by direct contact, more so when animal handlers and farmers deal with livestock.

Global Trends

Although the rising pressures of a rapidly expanding economy and a relatively lax regulatory environment indicate that low- and- middle- income countries shall drive the consumption of antimicrobials in the context of livestock rearing in the years to come, the problem of drug resistant food-borne bacteria has been recognised in many developed countries as well. The CDC’s newly-launched National Antimicrobial Resistance Monitoring System (NARMS) website provides an interactive tool to understand how the antimicrobial resistance pattern has changed in four food borne bacteria (Campylobacter, E. coli O157, Salmonella, and Shigella) over the last two decades.

A recent study which looks at global trends of antimicrobial use in animals (2) has predicted that by 2030, there will be a 67% increase in livestock related consumption of antimicrobials globally, and a major share of that will be contributed by the BRICS countries (Brazil, Russia, India, China and South Africa). The estimates show that the rate of antimicrobial consumption in these nations shall outstrip the rate of population growth by seven times.

The increasing demands on food security will make the shift towards an intensive, large-scale food production model more pressing, as rapidly expanding economies of middle income countries, make sub therapeutic usage of antimicrobials for growth promotion and productivity a necessary evil.

The 2013 Summary Report on Antimicrobials Sold or Distributed for use in Food-Producing Animals was released in April 2015 by the FDA. The report reveals that overall, there was 17% increase in the antimicrobial consumption in food-animal segment between 2009 and 2013; more worrisome was the trend that consumption of medically important antimicrobials rose by 20% in the same period. The report shows that the overall antimicrobial consumption for the food animal sector was 14.8 million kilograms, and medically important antimicrobials comprised 62% of this. This represents a large consumption of medically relevant drugs in clinically sub therapeutic dosage, which might lead to development of resistance through evolution pressure in circulating microbes.

The Way Forward

The issue of livestock-related emergence of antimicrobial resistant bacteria is a potentially preventable problem. Mandated withdrawal of use of antimicrobials to promote growth and productivity in livestock in some European countries has led to a marked reduction in the occurrence of drug resistant strains of microbes, but the duration of withdrawal and whether there is a possibility of re-introduction remain hotly debated topics. (3)

At the policymaking level there needs to be cognition of the fact that with the increasing pressures of rapid growth in population and demand for food security, there is bound to be some prophylactic and productivity-boost in the use of antimicrobials amongst livestock. There should however be concerted effort at multiple levels, both within the national and the international arenas, to promote a system of limiting overuse and identifying emerging risks.

In the short-to-medium term, there needs to be the institution of an international surveillance mechanism which identifies the emergent antimicrobial resistance in bacteria. Overall, antimicrobial consumption of livestock across borders, especially in countries that are experiencing a rapidly intensified livestock sector, is the need of the hour. Construction of open channels of communication and collaboration across sectors, involving the ministries dealing with agriculture and animal husbandry, human health and welfare, social and economic policies, and finance to keep the problem from snowballing into unmanageable proportions, is also an issue that calls for immediate attention.

In the long-term, there has to be research in newer pharmacologic and non-pharmacologic interventions that have potential to promote growth and productivity in livestock without having negative repercussions, as has been observed in case of antimicrobial overuse.


  1. Food and Drug Administration (2010) CVM Updates - CVM Reports on Antimicrobials Sold or Distributed for Food-Producing Animals (Food Drug Admin, Silver Spring. MD). Available at Accessed August 31, 2015.
  2. Van Boeckel TP, Brower C, Gilbert M, Grenfell BT, Levin SA, Robinson TP, Teillant A, Laxminarayan R. Global trends in antimicrobial use in food animals. ProcNatlAcadSci U S A. 2015 May 5;112(18):5649-54. doi: 10.1073/pnas.1503141112. Epub 2015 Mar 19. PubMed PMID: 25792457; PubMed Central PMCID: PMC4426470.
  3. Cogliani C, Goossens H, Greko C. Restricting antimicrobial use in food animals: Lessons from Europe. Microbe. 2011;6(6):274−279.