In the search for ways to counter the growing crisis of antibiotic resistance, there has been increasing scrutiny of antibiotic use in animals farmed for food. It is estimated that in certain countries, 80% of medically important antibiotic use occurs in the animal sector, primarily to promote growth in healthy animals.1
Experts have expressed concern that the widespread misuse of these drugs in agriculture is a primary contributor to antibiotic resistance in humans. “Antimicrobial use in food-producing animals can lead to selection and dissemination of antimicrobial-resistant bacteria in food-producing animals, which can then be transmitted to humans via food and other transmission routes,” according to the World Health Organization (WHO).2
Some of the antibiotics used in animals represent one of a very limited number of treatment options — or the last line of treatment — for serious infections in humans. Therefore, unnecessary use in this sector should be reduced to preserve the effectiveness of antibiotics in human medicine. “A lack of effective antibiotics is as serious a security threat as a sudden and deadly disease outbreak” said Tedros Adhanom Ghebreyesus, PhD, Director-General of WHO, in a press release.3 “Strong, sustained action across all sectors is vital if we are to turn back the tide of antimicrobial resistance and keep the world safe.”
The World Health Assembly’s global action plan on antimicrobial resistance also notes the importance of cross-sectoral involvement from a range of disciplines, including veterinary and human medicine. “This is a One Health issue, and both WHO and the World Organization for Animal Health (OIE) have joined forces and are calling on countries worldwide to take action against the rising threats from antibiotic-resistant bacteria,” said Cyril Gerard Gay, DVM, PhD, senior national program leader in Animal Production and Protection at the Agricultural Research Service of the United States Department of Agriculture. In 2015, the OIE and the Food and Agriculture Organization of the United Nations adopted resolutions in support of the global action plan.
The WHO recently published new guidelines regarding the use of medically important antibiotics in food-producing animals.2 The recommendations were directly informed by results of a large WHO-funded systematic review published in 2017 in The Lancet Planetary Health that examined the effects of interventions that reduce antibiotic consumption in farm animals.4
The findings demonstrated that such interventions were linked with a lower prevalence of antibiotic-resistant bacteria and multidrug-resistant bacteria in animals (by approximately 15% and 24%-32%, respectively). In addition, a meta-analysis of 13 of the studies showed that interventions to reduce antibiotic consumption in farm animals were associated with a 24% absolute reduction in the prevalence of antibiotic-resistant bacteria in humans, although the evidence pertaining to humans is less robust overall.
The new WHO guidelines call for the following actions regarding the use of medically important antibiotics in animals:
- Total restriction for purposes of growth promotion
- Complete restriction for purposes of disease prevention in healthy animals unless animals in close vicinity have been diagnosed with a disease that requires such use
- Testing of sick animals, when possible, to determine the most appropriate antibiotic for their infection
- Selection of antibiotics from the WHO list of those that are considered “least important to human health” and avoidance of those considered “highest priority, critically important”
Additional recommendations include vaccination of animals to reduce the need for antibiotics, as well as improved production, processing, and hygiene practices.
There is also increasing attention toward the identification and development of alternatives to antibiotics for use in animals. The US Department of Agriculture and the OIE jointly organized the 2nd Alternatives to Antibiotics International Symposium, which took place in Paris in 2016.5
The following key areas were explored in presentations and panel discussions:
- Vaccines that could reduce the use of medically important antibiotics
- Microbial-derived products, such as probiotics and bacteriophage gene products
- Non-nutritive phytochemicals, including prebiotics
- Immune-related products, such as antibodies, microbial peptides, and cytokines
- Chemicals, including enzymes
- Regulatory pathways to enable the licensure of alternatives to antibiotics
Since the last symposium, researchers “have begun implementing research programs to discover and develop alternatives to antibiotics that could reduce the need for them [and thus] safeguard important medical antibiotics,” said Dr Gay.
Numerous countries have acted to reduce antibiotic use in animals. For example, Denmark discontinued the use of antimicrobials for growth promotion in 1999, through a combination of regulatory measures and volunteer efforts by animal producers. A WHO expert committee determined that this intervention led to substantial reductions in antimicrobial use, antimicrobial resistance in animal reservoirs, and the related risk to public health.6
The WHO guidelines acknowledge that low and middle-income countries may require implementation support, such as “assistance with animal health management to reduce the need for antimicrobials, including improvements in disease prevention strategies, housing, and husbandry practices,” the authors wrote. “Furthermore, many countries may need technical and laboratory capacity building assistance for conducting the recommended bacterial culture and sensitivity testing.” They propose that the Food and Agriculture Organization and OIE could potentially provide such support when warranted.
In the new WHO guidelines regarding the use of medically important antibiotics in food-producing animals, recommendations include avoidance of use for disease prevention and growth promotion, as well as avoidance of antibiotics deemed by the WHO to be critically important to human health.
- Burki TK. Tackling antimicrobial resistance in food-producing animals. Lancet Respir Med. 2018;6(2):93–94.
- Aidara-Kane A, Angulo, FJ, Conly JM, et al; WHO Guideline Development Group. World Health Organization (WHO) guidelines on use of medically important antimicrobials in food-producing animals. Antimicrob Resist Infect Control. 2018;7:7.
- World Health Organization (WHO). Stop using antibiotics in healthy animals to prevent the spread of antibiotic resistance. http://www.who.int/mediacentre/news/releases/2017/antibiotics-animals-effectiveness/en/. November 7, 2017. Accessed March 13, 2018.
- Tang KL, Caffrey NP, Nóbrega DB, et al. Restricting the use of antibiotics in food-producing animals and its associations with antibiotic resistance in food-producing animals and human beings: a systematic review and meta-analysis. Lancet Planet Health. 2017;1(8):e316-e327.
- Alternatives to Antibiotics. https://www.ars.usda.gov/alternativestoantibiotics/Symposium2016/. 2016. Accessed March 13, 2018.
- World Health Organization. Impacts of antimicrobial growth promoter termination in Denmark: the WHO international review panel’s evaluation of the termination of the use of antimicrobial growth promoters in Denmark: Foulum, Denmark, 6-9 November 2002. Geneva: World Health Organization.