Eleven questions on antimicrobial resistance in animal health

What is antimicrobial resistance?

Antibiotics are substances that fight infection-causing bacteria. They began to be used on a large scale after World War II. They led to major medical breakthroughs, enabling the treatment of previously incurable diseases and increasing human life expectancy. However, their frequent and sometimes unjustified use (for non-bacterial infections, treatment periods that are too short or too long, unsuitable doses), in both human and veterinary medicine, has contributed to the multiplication of bacteria that are resistant to these treatments, via the selection of strains capable of surviving antibiotics. These resistant bacteria can be transmitted from animals to humans, and vice versa.

Why are antibiotics used in animal husbandry?

The use of antibiotics in animal husbandry is mainly to treat sick animals. Treatments to prevent the onset of an infectious bacterial disease before the appearance of clinical signs (preventive use called prophylaxis), or administered to a group of animals following the diagnosis of a bacterial infection in one or more of these animals (preventive and curative use called metaphylaxis), are highly regulated. They are only permitted when no other solution is possible to avoid infection of the animals and spread of the bacterium.

Antibiotics are administered on prescription and under veterinary supervision. All uses of antibiotics in animal health are subject to European regulations restricting their use, in order to limit the development of antimicrobial resistance.

Are antibiotics added to feed?

Since 2006, a European regulation has prohibited the use of antibiotic growth promoters in animal feed. However, antibiotics for therapeutic purposes may be added to feed to facilitate their oral administration to an animal or group of animals. They must be prescribed following a diagnosis by a veterinarian.

What legislation governs the use of antibiotics for pets and livestock?

European Regulation (EU) 2019/6 on veterinary medicinal products, which came into force in January 2022, further strengthens the framework for the administration of antibiotics and antimicrobials to animals:

• extension of the ban on the use of antimicrobials as growth promoters (which already applied to animals produced in the EU) to all animals and animal products imported into the EU,
• mandatory veterinary prescription for veterinary medicines containing antimicrobials in all European countries,
• restriction on the use of antimicrobial veterinary medicinal products for prophylaxis (administration of a medicinal product to an animal or group of animals before clinical signs of a disease, in order to prevent the occurrence of disease or infection),
• restriction on the use of antimicrobial veterinary medicinal products for metaphylaxis (administration of a medicinal product to a group of animals after a diagnosis of clinical disease in part of the group has been established),
• a total ban on veterinary use of certain compounds reserved for the treatment of infections in humans, in order to preserve the efficacy of antimicrobials,
• consideration of the risk of emergence of antimicrobial resistance for marketing authorisations.

What are the consequences of antimicrobial resistance for animals and humans?

Today, numerous bacteria are resistant to several different antimicrobials (multidrug resistant). This phenomenon compromises the efficacy of the available treatments and threatens human and animal health. The emergence of resistance to an antibiotic results in this antibiotic becoming less effective in treating infections caused by the resistant bacteria in animals or humans.

There are some situations that result in therapeutic dead-ends, when there are no longer any antibiotics effective against a bacterium.

This resistance can spread to the environment, be transmitted to other bacteria and cause cross-resistance to other antibiotics. Combating antimicrobial resistance therefore requires an overall approach, encompassing humans, animals and the environment. For this reason, actions against antimicrobial resistance must address human health, animal health and the environment according to a "One Health" approach.

What is a critical antibiotic?

Certain antibiotics are considered critically important to human health because they are the only ones, or among the few, that can treat serious diseases in humans. This is the case with third- and fourth-generation cephalosporins and fluoroquinolones. Their use is therefore regulated in veterinary medicine and should only be considered as a last resort.

How can the spread of antimicrobial resistance in animals be prevented?

To prevent and combat the spread of antimicrobial resistance, certain precautions can be taken:

• only give antibiotics to animals under veterinary supervision and in accordance with the prescription,
• only use antibiotics when necessary, complying with the recommendations by animal species and the regulatory requirements,
• vaccinate animals to reduce the need for antibiotics and opt for alternatives to these drugs, if available,
• improve hygiene and animal welfare to avoid infections,
• wash hands before and after touching an animal to avoid the transmission of antibiotic-resistant bacteria from animals to humans or between animals.

What is ANSES's role in combating antimicrobial resistance in animal health?

ANSES is the National Reference Laboratory (NRL) for antimicrobial resistance. It also coordinates RESAPATH, the only network of its kind in Europe, for monitoring resistance in pathogenic bacteria of animal origin. In addition, it is responsible for issuing marketing authorisations for veterinary medicines.

ANSES's work therefore includes:

• monitoring and studying the presence of bacterial resistance in animals and in food of animal origin,
• monitoring exposure to antimicrobials and assessing the risks associated with antimicrobial resistance as part of the marketing of veterinary antimicrobials,
• participating in European and international reference work on antimicrobial resistance,
• conducting research to better detect and understand antimicrobial resistance.

Learn more about ANSES's missions on antimicrobial resistance in animal health

Which bacteria are monitored for antimicrobial resistance in animal species?

RESAPATH tracks a range of pathogenic bacteria in animals.

For food-producing animals, three groups of bacteria of importance to human health are also monitored throughout the European Union:

• Salmonella, the main cause of food poisoning in Europe,
• Campylobacter, the leading cause of gastroenteritis in Europe,
•  Escherichia coli, in order to estimate the reservoir of circulating resistance.

What is the level of animal exposure to antimicrobials?

Since 2011, the overall exposure of animals to antimicrobials has halved (-47% between 2011 and 2021). The objectives of the EcoAntibio plan (2012-2016), which aimed to reduce antibiotic use by 25% within five years, and then of the EcoAntibio 2 plan (2017-2021), whose goal was to ensure that this decline was sustained, were achieved. The EcoAntibio 2 plan also aimed for a 50% reduction in the use of colistin, an antibiotic that is commonly used in veterinary medicine and is reserved for severe cases in human medicine. This objective was also achieved, since this decrease was 68.8% in 2021, compared to the reference level from 2014-2015, for the cattle, swine and poultry sectors. The target of a 50% reduction, which had been set by the EcoAntibio 2 plan, was therefore met.

How has the rate of antimicrobial resistance in animals changed in the last few years?

Created in 1982 and coordinated by ANSES, the French Surveillance Network for Antimicrobial Resistance in Pathogenic Bacteria of Animal Origin (RESAPATH) monitors veterinary antimicrobial resistance. Since the start of the monitoring programme, the rate of antimicrobial resistance has decreased by varying degrees depending on the animal sector and antibiotic.

In 2022, the trends in antimicrobial resistance remain generally favourable. Apart from amoxicillin and amoxicillin-clavulanic acid, there has been a decline in resistance or the level has remained stable for most antibiotics. This is particularly the case for cephalosporins and fluoroquinolones, which are of critical importance to humans and whose efficacy in human medicine must be preserved. The proportion of strains resistant to these antibiotics has remained very low (below 8%) for several years. Resistance to colistin, another antibiotic of interest, also remains low in all animal species.