Expert's voice

Interview: Antimicrobials use in animals – why, when and how?

The World Organisation for Animal Health (WOAH) has recently released a landmark report with trends on the global use of antimicrobials in animals. In this interview, Dr Javier Yugueros-Marcos, Head of the Antimicrobial Resistance and Veterinary Products Department, elaborates on some of the key findings.
Dr Javier Yugueros-Marcos, Head of the Antimicrobial Resistance and Veterinary Products Department

The report shows a decrease in the use of antimicrobials in the animal health sector, but is this enough to curb the development of antimicrobial resistance (AMR)?

JYM: We are pleased to see steady progress in the way antimicrobials are used in animals. From 2016 to 2018, the global amounts used in animals have declined by 27%, according to the data1 reported to our Organisation. These are encouraging results as they show the commitment of the animal health sector, from farmers to veterinarians, to address this global health challenge. These efforts also contribute to protect everyone’s health, as drug-resistant bacteria can spread between and within animals, humans, plants and through the environment.

Yet, much more still needs to be done to fight antimicrobial resistance and preserve the efficacy of these critical medicines. It is important to rely on practices in animal production systems that reduce the need for antibiotics, by preventing diseases in the first place. Biosecurity measures and good animal husbandry can have an enormous impact in reducing the risk of introduction, establishment and spread of infections in animals. Concurrently, appropriate funding needs to be provided to support the research for alternatives to antimicrobial use, including vaccination, for instance.

Core to making more progress is to increase our knowledge and understanding around how, when and why antimicrobials are used worldwide. The database created by the World Organisation for Animal Health in 2015 contributes to this knowledge, as it enables countries to gain a good understanding of their situation and measure progress and efficiency of actions over time.  

Tetracyclines are the most used antibiotics in animal health globally. Why is this happening? Does it pose a risk for the development of resistance?

JYM: Tetracyclines are one of the earliest discovered family of antibiotics. They were found in 1944, not long after penicillin was discovered by Alexandre Fleming. Tetracyclines have a very broad spectrum of activity, meaning that they can act against a wide range of disease-causing bacteria. They are easily available worldwide and much cheaper compared to other broad-spectrum antibiotics (e.g., fluoroquinolones). In terrestrial food-producing animals they can be used as first line treatment to numerous diseases in various species, including large ruminants (listeriosis, mycoplasmosis, etc.), swine (respiratory and gastrointestinal diseases, neonatal septicemia, etc.), poultry (respiratory diseases, coccidiosis, arthritis, etc.), among others.

As with every antimicrobial, when tetracyclines are misused or overused, there is a risk to select resistant pathogens. While some studies show a relationship between use in animals and resistance observed in humans, more research is needed to fully understand the implications. AMR is a complex phenomenon that can originate in animal, human or plant populations, and which can then pose a threat to all the other species.

Integrated surveillance, which allows to gather data from across sectors, is essential to monitor and take preventive actions before it is too late. This is why we are working with our Quadripartite partners – the Food and Agriculture Organization of the United Nations (FAO), the United Nations Environment Programme (UNEP) and the World Health Organization (WHO) – to reinforce surveillance at national level, integration of regional and global data, and cross-sectoral analyses.

The report also highlights a decrease in the use of “critical” antimicrobials in animals. What else could be done to preserve the efficacy of these specific antimicrobials that are essential to human medicine?

It is worth emphasising that antimicrobials are important for both human and animal health. In 2006, we developed a list of antimicrobial agents of veterinary importance. Within this list, we provide recommendations to our Members for those antimicrobials that are considered as highest priority and critically important for human health by WHO. The aim of our recommendations is to discourage their use in animals. This means that these critical antimicrobials should not be used as first line treatment unless justified by evidence (e.g., findings of antimicrobial susceptibility testing), or to boost growth in healthy animals, for instance. Yet, in some specific situations, their use may still be necessary to ensure animal health and welfare.

Such list serves as a reference for countries to develop their own guidelines to ensure responsible use of antimicrobials in food-producing animals.

Antibiotics are still used in healthy animals to boost growth in at least 40 countries. What is the position of the World Organisation for Animal Health on this kind of practice?

JYM: Any use of antimicrobials in animals should be in line with our international Standards, which encourage responsible and prudent practices. These evidence-based Standards are published in our Terrestrial and Aquatic Codes. According to these recommendations, the use of antimicrobial agents for growth promotion in the absence of a risk analysis is not deemed to be responsible use. Noteworthy, for those antimicrobials considered as highest priority and critically important by WHO, we do urge Members to phase out their use as growth promoters and explore alternatives to enhance productivity.  

In addition to this, we work closely with veterinary authorities to make sure that these guidelines are adapted and deployed at national level. Equally relevant, we support the development of awareness campaigns to promote the prudent use of antimicrobials and the implementation of good husbandry and biosecurity practices to prevent diseases in animals. 

Why can the data presented in the report not be accessed by country?

JYM: The report provides global and regional overviews of the use of antimicrobials in animals. The data is not broken down by country as the aim of our database is to foster the participation of the greatest number of countries, without pointing out potential gaps in national capacities.

Nevertheless, we do encourage countries to use their available data to better understand their national situation and measure the progress and efficiency of their actions over time. The information collected can be published on national platforms and countries that are already doing this are referenced in the report (Section 11). In the near future, our new interactive and customised online system (ANIMUSE) to collect and report antimicrobial use data will allow countries to explore and analyse their data through an interactive dashboard. 

Can we compare the data on the use of antimicrobials between animals and humans?

JYM: One of the major advances achieved in our data collection and analysis process over the past years, was to be able to adjust the quantities of antimicrobials used in animals to their biomass. This parameter is key to draw relevant comparisons of the amounts of drugs used across different animal species, regions and over time and hopefully soon with humans. Animal biomass is calculated as the total weight of live domestic animals in a given country and year. Since antibiotics are used differently depending on animal species and types of animal production systems, variation in the species composition of regional biomass may explain some of the differences noted in antimicrobial consumption across countries and regions.

However, to date, it is not possible to compare our global data on animals to the quantities of antimicrobials used in the human health sector. While some countries are able to do so (e.g., Canada and countries from the European Union), achieving this at global level is more challenging. To address this gap and have a better picture of antimicrobial use and antimicrobial resistance across sectors, we are collaborating with the World Health Organization and the Food and Agriculture Organization of the United Nations on the development of a joint platform. The latter will have an important role in supporting policy makers in the development of relevant strategies against antimicrobial resistance under the One Health approach.

Could the use of antimicrobials in animals be banned and replaced with vaccines and good animal husbandry practices?

JTM: Vaccines and good animal husbandry are both core measures to prevent disease and are central components of the fight against AMR, but sometimes animals still fall ill and need treatment.

Unfortunately, we do not have vaccines available for all diseases, thus, an outright ban on antimicrobials would be damaging for animal health and welfare, as well as the livelihoods of farming communities. This would consequently have a negative impact on national economies and food security.

Antimicrobials are needed to fight infectious diseases in animal health too. But they must be used in a  responsible manner, only when necessary, when biosecurity and husbandry fail, and when there are no other alternatives available. That’s what we advocate for at the World Organisation for Animal Health.

1 Based on the data reported by 72 countries to the World Organisation for Animal Health for all years between 2016 to 2018.