Interview – "The One-Health approach is not new. But it was neglected by many scientists for a long time"

It was due to the health crises in recent years that the links between human health, animal health, and ecosystem health have come to the forefront in scientific research, says Dik Mevius.

​Mister Mevius, your keynote lecture was titled "Antimicrobial Resistance, a complex One-Health problem". Can you briefly explain the notion One-Health?

One-Health means that the evolution of antimicrobial resistance is not solely confined to human health care but is also associated with animals and the environment. Antimicrobial resistance has evolved dramatically on a global level over the last 10 to 20 years, and that's the result of many intertwined processes in and between the human, animal and environmental domains. Therefore, to control antimicrobial resistance, research and interventions should not focus on one single domain, but aim to work at the interface between them.

The view that all these domains are interconnected does not seem new. Why has it only recently gained such an attention?

Indeed, this view is not new. But it was neglected by many scientists for a long time. It has taken the health crises in recent years like BSE, bird flu or MRSA to highlight the manifold relations between domains and their potential consequences. Of particular importance was the Q Fever outbreak in the Netherlands from 2007 to 2010. Q Fever is caused by relatively rare bacteria, which are most often found in cattle, sheep and goats, but also in pet animals like cats and dogs. They can be transmitted to humans where they lead to symptoms like pneumonia in around half of all cases. During the Q Fever outbreak in the Netherlands, thousands of people got ill and more than 25 patients died.

The infections were transmitted from animals?

The inhalation of aerosols from contaminated soil or animal waste from commercial dairy goat farms was the main cause of the epidemic.

What measures were used to deal with this crisis?

As an emergency intervention, thousands of goats were culled to stop the disease from spreading further. Then, preventive interventions like vaccinations and hygiene measures on dairy, goat and sheep farms were implemented. The most important lesson was that veterinary and human medicine have to collaborate more closely. The Q Fever outbreak could have been averted at an earlier stage if there had been a better exchange of information.

So, the crisis led to new thinking about One-Health in general?

The Q Fever outbreak was a catalyst, creating awareness about the huge importance of the One-health approach. Sixty percent of human infectious diseases are zoonotic, which means they can be transmitted between animals and humans. The number is even higher when emerging infectious diseases are concerned.

Which can become resistant to antimicrobial drugs.

Yes, that's why a reduction of resistance in the animal domain may contribute to a reduction of resistance in the human domain. However, to effectively contain antimicrobial resistance, we need to implement interventions in all domains, with the impact on other domains in mind. Furthermore, we have to investigate the exact mechanisms of resistance evolution and spread across domains. Because the problem is not only resistant pathogens, which are transmitted.

You have to explain that.

Non-pathogenic microbes and even single genetic elements, which are transmitted across domains, can also support the development of resistance in human pathogens already present. That's because bacteria have the ability to transfer genetic information between each other. And if resistant human pathogens in turn get into wastewater and animal domains, they may again lead to large reservoirs of resistance determinants, which again can lead to the development of new resistance variants in human pathogens later on. Currently, these processes are not very well understood and are poorly quantified.

In your presentation, you showed, that on the one hand, Dutch food-producing animals are an ideal environment for multidrug resistant organisms, but on the other hand, the resistance situation in human medicine in the Netherlands is quite good. Doesn't that challenge the view that domains are so closely interrelated?

In the Netherlands, the resistance situation in human medicine is quite good at the moment because effective infection control measures are in place and antibiotics are used very restrictively. But organisms in animals and the environment generally do not pose a direct threat to public health. They don't contribute massively to infections in humans. The relationships between domains are more complex and they have a predominantly evolutionary nature. They enhance the chance of new resistance variants, which are of concern to public health in relation to the emergence and spread of disease. It's this evolutionary aspect that has led to the global resistance problem we actually see.

But in the Netherlands, it hasn't led to a big problem yet?

In countries like the Netherlands and Switzerland, we may still be able to deal with the problem for a while with big efforts in health care. But if we don't control it in a One-Health way, in the long run we'll end up in a situation like other countries, where it is already very difficult to treat humans with infections.

Do you think scientists can discover crucial aspects of the processes in and between domains in the coming years and find solutions to stop or slow them?

In recent years, new scientific methods and instruments have been developed, which have fundamentally changed our ability to address questions of development and spread of resistance across domains. We can now sequence and compare huge amounts of genetic data in a very short time. That's key to effectively investigate the interrelations of resistance variants and to ultimately discover the processes that affect their evolution.

The Netherlands as a pioneer already has quite a lot of experience with research collaboration between human medicine, veterinary medicine and environmental sciences in the field of antimicrobial resistance. How well does this cooperation work?

It works fine. But this took some time of course because the different domains have to get to know each other, especially their respective roles in One-Health related issues of zoonotic diseases. Somehow you can say that in the Netherlands, it helped that we had these public health crises. They made us realize that we have to approach such issues in a One-Health way. This awareness is key for developing a close collaboration between the involved disciplines. Once such partnerships are established you can make big steps.

New approaches for solutions, coming from science, are one thing. But they have to be translated into practice. What is the experience of the Netherlands in this regard?

Researchers have to identify hazards, characterise risks and show possible solutions in a way that convinces risk managers to initiate measures. Therefore, an active interaction between research, authorities and private stakeholders is crucial. I think Switzerland is on a good path in this regard, since it's already in the implementation phase in many fields, with a coordinated national strategy against antibiotic resistance. Despite the problem being a global one, every country has to develop its own measures because measures have to suit the local conditions, be adapted to the structures of the health sector, of the agriculture sector, to the political realities and other national peculiarities. This requires awareness of the complex interrelations between domains, and it needs time.