3 The importance of a One Health approach to tackling AMR

This figure shows four circular compartments labelled ‘Human health’, ‘Animal health’, which overlaps with a separate circle for ‘Animal production’, and ‘Agriculture’. At the bottom of the diagram a bar represents the environment and includes the words ‘Water’ and ‘Soil’. In the centre of the diagram is a rectangular compartment labelled ‘Food chain’. The compartments are linked by arrows that are each labelled with a letter corresponding to a detailed description which is also found in the PDF. Description relating to each letter in the PDF is included in this explanation so you can access it conveniently.

Within the human health compartment letters A, B and C are used. These represent important drivers of AMR in people. A is described as:

• correct and/or prolonged use of antimicrobials for clinical treatment, plus uncontrolled public access to antimicrobials
• poor hygiene in hospitals, inadequate sewage and water treatment, and poor hygiene in the community contribute to the transmission of AMR amongst people
• people travelling overseas, especially those hospitalised in hospitals with poor infection control and antimicrobial prescribing practices, may acquire resistant bacteria and genes that are subsequently transmitted in hospital and/or into community environments.

B refers specifically to hospital-acquired infections (HAIs), which occur through the spread of ARB and/or ARG to people within hospitals. This may include transmission between patients and/or staff either directly or through equipment and materials in hospitals. It is generally associated with poor infection prevention and control practices.

C refers to community-acquired infections (CAIs), which occur through the transmission of ARB and/or ARG in community settings (i.e. outside hospital settings). Direct human-to-human transmission may occur as a result of poor personal hygiene, e.g. inadequate hand-washing.

E connects the human and animal health compartments. ARB and/or ARG may be transmitted from sick pets or livestock to their owners or livestock managers through contact and poor hygiene, such as inadequate handwashing. Transmission of ARB and/or ARG from humans may cause illness in animals as a result of contact and poor hygiene.

Within the animal health compartment, pets and livestock are considered. D indicates the important drivers of AMR in animals associated with clinical treatment of pets and livestock:

• Incorrect and/or prolonged use of antimicrobials to treat sick animals, plus uncontrolled public and farmer access to antimicrobials.
• Poor hygiene in veterinary clinics, poor biosecurity and hygiene on farms contribute to the transmission of AMR within these settings.

In addition ARB and/or ARG may spread among pets within veterinary clinics or boarding kennels, associated with poor hygiene, indicated by F, and among livestock through overcrowding, poor disease control and hygiene within farm environments, indicated by letter G.

Within the overlapping animal production compartment, livestock and aquaculture are named. Letters I and J describe poor biosecurity, poor hygiene and overcrowding of animals, or of aquatic species respectively, which can contribute to the transmission of AMR within farms.

More generally, H describes important drivers of AMR in farmed animals and aquatic species:

• Prolonged administration of sub-therapeutic levels of antimicrobials to enhance growth and productivity, most commonly in intensively farmed animals, e.g. pigs, poultry and aquatic species.
• Administration of therapeutic doses of antimicrobials to groups of animals to prevent clinical disease (prophylaxis) or to prevent spread of clinical disease if some animals in the group show symptoms (metaphylaxis). This is to reduce chances of the remaining animals becoming ill. This is most common in intensively raised pigs, poultry, feedlot calves and aquatic species.
• Poor biosecurity, poor hygiene and overcrowding can contribute to the transmission of AMR within and between farms.

International trade of animals can contribute to the importation of ARB and/or ARG and the movement of animals within a country contributes to local spread.

A double-headed arrow linking human health to animal production is labelled K. This explains that ARB and/or ARG may be transmitted from livestock and aquatic species to people through direct contact in the farm environment, or during transport and processing.

Within the agriculture compartment, L describes drivers for AMR in fruit and vegetable crops, which include:

• repeated use of antimicrobials to treat or prevent bacterial diseases, particularly if administered at sub-therapeutic levels
• rain and wind and poor equipment hygiene may contribute to the spread of resistant bacteria within and between crop farms/orchards – trade and the movement of plant material and/or equipment may contribute to the transmission of resistance between crop farms/orchards.

In addition, M labels food crops and explains that AMR can spread between plants via wind, rain and unhygienic equipment.

Arrows labelled N connect all three non-human compartments to a box labelled ‘Food chain’. N explains that ARB and/or ARG may be carried on the surface of fresh food products, including food animal products (including aquatic species) and fruit, vegetables and grains.

Arrows from the food chain box to human health, and in the opposite direction, are labelled P and O respectively. P represents food contamination in which people may become infected with ARB and/or ARG by consuming contaminated food. O represents food handling during which food may also be contaminated with ARB and/or ARG by people handling food during processing, transport, retail and preparation of meals.

The human health compartment is linked to the environment compartment by Q, which explains that people excrete resistant bacteria in their faeces or urine. These bacteria enter waterways and drinking water sources through poorly maintained sewage systems and inadequate sewage treatment. Inadequate treatment of hospital waste may also contribute ARB and/or ARG in sewage and waterways.

Both the animal health and animal production compartments are linked to the environment by arrows labelled R. R explains that ARB and/or ARGs in animal waste enter waterways and drinking water sources through disposal of untreated effluent and water run-off from farms after heavy rain and/or flooding and/or via irrigation.

Animal production is linked to agriculture by an arrow labelled S. S explains that ARB and/or ARG may be transmitted by spreading manure from animals onto fruit, vegetables and grain crop farms. ARB and/or ARG from human faeces may also contaminate fruit, vegetables and grain crops and/or their environment.

Agriculture is linked to the environment by an arrow labelled T, representing slurry and run-off. T explains that ARB and/or ARG may be spread from fruit, vegetable and crop farms by run-off into surrounding waterways following rain and/or irrigation.

An arrow labelled ‘Waste’ links the food chain box to the environment and is labelled U. U explains that ARB and/or ARG present during processing of meat, vegetable and fish products may be spread into waterways via slaughterhouse effluent, and/or inadequate sewage systems.

The letter V is found within the environment compartment, and describes drivers of AMR in environmental compartments such as soil and water. In summary, the presence of ARB and/or ARG from human, animal and plant sources in the environment with subsequent transmission of ARG to environmental bacteria via mobile genetic elements.

The environment is linked to the human health compartment by an arrow labelled W, which explains that people can become infected with ARB and/or ARGs through contaminated and poorly treated drinking water and swimming or bathing in contaminated river/lake water, contact with flood water.

The environment is linked to agriculture by an arrow labelled X, which explains that food crops may become contaminated with ARB and/or ARGs through contaminated water.

The environment is linked to the agriculture compartment by an arrow labelled Y. Y explains that animals may become infected with ARB and/or ARGs from contaminated drinking water or irrigation water used to grow feed crops. Aquatic species may become infected with ARB and/or ARGs through contamination of the water in which they are raised with water from other environments entering the farm water e.g. upstream water that runs through an urban and/or livestock farming area.

To the right of the environment compartment a separate box is labelled ‘Wildlife’. This is connected to the environment by arrows in both directions labelled Z. Z explains that ARB and/or ARGs may be transmitted to wildlife via water that has been contaminated in other urban and farming environments.