Frequently Asked Questions
- What is an antimicrobial drug?
- What are antibiotics used for?
- How does antibiotic use in animals affect humans?
- What is Antimicrobial Resistance (AMR)?
- How does the emergence of AMR in animals affect human health?
- Are the antimicrobials used in animals the same ones used in people?
- Is antimicrobial use in farm animals responsible for the spread of resistant bacteria?
- What are food producers doing to prevent antimicrobial resistance?
- What procedures does a producer need to follow when using antimicrobial products?
- What is the withdrawal time for antimicrobials?
- Where can I get further information on AMR?
An antimicrobial is a drug that kills microorganisms or stops their growth. Antimicrobial medicines can be grouped according to the microorganisms they act primarily against. For example, antibiotics are used against bacteria and antifungals are used against fungi.
Antibiotics are medicines useful for controlling and preventing infectious disease in livestock. Proper use can keep animals healthy, control the spread of diseases between herds, and prevent the spread of diseases from animals to humans.
Research has provided strong evidence that antibiotic use in food animals can lead to resistant infections in humans. Resistant bacteria in food can cause infections in humans.
Antimicrobial resistance (AMR) is where the medicines (e.g. antibiotics) used to treat diseases caused by specific micro-organisms (e.g. bacteria) are no longer effective. Antibiotic resistance does not mean the body is becoming resistant to antibiotics; it is that bacteria have become resistant to the antibiotics designed to kill them.
The emergence of AMR in livestock has been shown to affect human health through the following mechanisms:
- Contamination of meat, milk, and egg animal products;
- Direct contact with animals
- Contamination of the environment, for example, through spreading animal manure on fields as fertilizer and pollution of water; and through providing a ‘reservoir’ of resistance genes.
Antimicrobials and antibiotics are grouped in “classes” based upon their mechanism of action (how they affect the bacteria, viruses and fungi). There are only a few classes that are specific to either human medicine or veterinary medicine. In fact, the vast majority of antibiotic classes are used in both humans and animals, so there really is no such thing as “human drugs used in animals.”
Many antimicrobials used in human medicine are not approved for use in animals or are, quite simply, too expensive to use in animals. When antimicrobials are needed for an animal, veterinarians base their choices on many factors, including:
- the type of infection;
- the organism causing the infection and its susceptibility (either likely susceptibility based on prior experience and knowledge, or susceptibility based on the results of laboratory testing) to the antimicrobial;
- the method by which the antimicrobial is given (whether it’s given orally or by injection, for example) and how that will be tolerated, as well as whether or not it should be given to the animal that way;
- whether or not it is approved for use in that animal species;
- the risk of side effects;
The use of antimicrobial drugs in agriculture is a contributing factor in the emergence of resistant pathogenic bacteria. However, there are other significant factors, such as the overuse and inappropriate use of antibiotics in human medicine.
Keeping animals healthy is the main goal – after all, sick animals aren’t allowed to enter our food chain – and healthy animals are less likely to become infected and are more likely to successfully fight off infection if they’re exposed to an infectious organism e.g a pathogen. The use of vaccines, parasite treatments, good nutrition and good management and husbandry to reduce stress and minimize the risk of disease are all necessary strategies. It is also reasonable to expect producers to use antimicrobials prudently.
When producers use antimicrobials and other medications, they are required to follow the label directions, which include the withdrawal times for the medications.
The withdrawal period is the amount of time (days, weeks or months) after the last treatment (or dose) has been given that the animal’s milk must be discarded or the amount of time before it can be slaughtered. The withdrawal times are based on how the body processes the medications, and observing them ensures that there are no drug residues in the milk or meat.
Other frequently asked questions on AMR are available at: