A global approach to human and animal health

With a holistically integrated approach based on farm, feed and health management, antibiotic use can be reduced significantly on a global scale – with equal or even improved productivity.”

Knut Nesse, CEO of Nutreco at the UN High-level Meeting on Antimicrobial Resistance (New York)

Just as microbes know no borders, there are no borders between human and animal health. This led to the collaboration between the United Nations FAO, OIE and WHO, which produced a Tripartite Concept Note addressing health risks at the animal-human-ecosystems interfaces. (ref.32)

Bacteria are constantly being exchanged between animals and humans. Animals may carry infectious agents and can contract many infections which are similar or identical to those affecting humans. In some settings, intensive livestock production, fish and seafood farming, and the medical care of household pets rely on the same types of antibiotics as those used to treat people. Antibiotics are often used to treat sick animals, but sometimes also as a preventive measure to protect healthy animals when they are in contact with sick ones or during periods when animals are travelling or exposed to other stress factors. (ref.33) Antibiotics are also sometimes used as growth promoters for livestock, even in the absence of disease: the benefit of this practice is controversial and it has been partially or totally banned in a number of countries, including Mexico, Brazil, Australia, New Zealand, Vietnam and the European Union. The WHO recommends that farmers and the food industry stop using antibiotics routinely to promote growth and prevent disease in healthy animals (ref.115).

The FAO estimates that, every year, 62 billion animals are used for the production of meat, milk and eggs, a figure which is likely to double by 2050. In many countries, the number of chicken and cattle far exceeds that of the human population. Globally, the total biomass of livestock is two and a half times that of the human population. (ref.34) It is therefore not surprising that the majority of antibiotics sold worldwide are used by the meat, dairy and aquaculture industries. Moreover, increasing worldwide demand for meat has led to antibiotic consumption in animals rising by 70% over the past decade. (ref.53) Estimates for some countries point to as much as 80% of antibiotics being consumed by livestock. (ref.35)

“One Stop Shop” web portal

“One Stop Shop” web portal

The U.S. Department of Agriculture has launched a “One Stop Shop” web portal for One Health information. The site aims to contribute to training and educating animal health professionals on several issues related to antibiotic resistance and focuses on 3 main areas: antimicrobial resistance, avian influenza, influenza in swine.

Antibiotic-free meat

Some restaurants and fast-food chains now advertise antibiotic-free meat in their menu. Raising antibiotic-free animals may be more expensive in some regions or countries, but many consumers are willing to pay more to avoid the risk of eating food containing antibiotics or antibiotic-resistant bacteria.

 Video by Euronews on the use of antibiotics in a pig farm in Catalonia.

Video by Euronews on the use of antibiotics in a pig farm in Catalonia.

Assessing the burden of disease caused by antibiotic resistant bacteria in the veterinary sector and its impact on humans at the global level is complex. However, in countries where data is available, use of antibiotics in livestock tends to correlate with antibiotic resistance in pathogens affecting humans. In its 2011 report Tackling antibiotic resistance from a food safety perspective in Europe, the WHO stated that “resistance in the food-borne bacteria Salmonella and Campylobacter is clearly linked to antibiotic use in food animals, and food-borne diseases caused by such resistant bacteria are well documented in people.”

ECDC/EFSA/EMA joint reports unveiled a wide array of correlations between consumption of antimicrobial agents by humans and food-producing animals and occurrence of antimicrobial resistance in bacteria. (ref.36) (ref.107) Furthermore, extensive monitoring in slaughterhouses and retail outlets in 28 EU countries in 2016 revealed very high levels of multidrug resistance in some strains of Salmonella. (ref.37)
To assist countries in applying a One Health approach, the WHO Advisory Group on Integrated Surveillance of Antimicrobial Resistance developed a new guidance document. (ref.108) To steer evidence-based policies, this guidance recommends to monitor:

  • Prevalence of AMR in different reservoirs;
  • AMR trends over time;
  • Association between AMR and the use of antimicrobial agents.

Interventions that restrict antibiotic use in food-producing animals have often been associated with a reduction in the presence of antibiotic-resistant bacteria in these animals. (ref.109)

Bacteria and the environment

All environmental compartments are connected. Humans and animals constantly exchange pathogenic or non-pathogenic bacteria, with or without resistance to antibiotics. These bacteria can easily spread into the environment though different routes.

The spread of antibiotic resistance

The spread of antibiotic resistance

Humans, pets, livestock and fish farms rely on similar classes of antibiotics to fight infectious diseases. Both pathogenic and non-pathogenic bacteria evolve or exchange the ability to survive when exposed to these antibiotics. Then, they can spread into the environment through different routes, e.g. through water sanitation systems (ref.01), as wastewater treatment facilities do not entirely remove antibiotic resistant bacteria before releasing water into waterways. Another common route is through the application of animal manure containing resistant bacteria to fields with cultivated crops (ref.02), where such bacteria can flourish on plants (ref.03).

The uptake of these resistant bacteria can then happen through the food chain, when humans later consume these plants (ref.04) or the contaminated flesh of animals and fish harbouring resistant bacteria (ref.05). As bacteria can easily reach water reserves, water distribution infrastructure is also a potential route for the spread of these bacteria (ref.06). Even wildlife, insects and other bugs are potential carriers of antibiotic resistant microbes (ref.07). Tourism, migration and food imports (ref.08) are nevertheless reported as the fastest way of spreading resistant strains of bacteria across borders.

At the healthcare facility level, resistant bacteria can spread by contact between patients or with healthcare staff, or through contaminated surfaces and medical devices.

Reservoirs of antibiotic-resistant bacteria

Reservoirs of antibiotic-resistant bacteria

Foodborne transmission of resistant bacteria is a common route for the spread of antibiotic resistance. Treating livestock with antibiotics can also be detrimental for the farmers’ health, as they can acquire resistant bacteria from the animals and transmit them to others. Several studies have revealed high transmission rates of MRSA between animals and farm workers. (ref.39)

Resistant bacteria from human sources have been detected in sewage treatment plants, in treated water released into the environment and in sludge applied to farmland. The highest concentrations of antibiotics and resistant bacteria are recorded in effluent released from hospitals and drug manufacturing sites in developing countries. (ref.40)