Governments and researchers need to pay greater attention to the spread of antimicrobial resistance -- or so-called superbugs -- in wildlife and the natural environment, according to a new study published in the Journal of Applied Ecology.
The threat posed by superbugs to human health is well known. But, the study warns, data on antimicrobial microbial resistance in wildlife are scarce.
"Superbugs are not restricted to humans and domestic animals. Antimicrobial resistance is present almost everywhere in the environment and in wildlife. Unless we take this into account we will be unable to control the spread of antimicrobial resistance effectively," says lead author Dr Marion Vittecoq of the Tour du Valat -- Research Institute for the Conservation of Mediterranean Wetlands.
Overuse of antibiotics in humans and livestock has led to rising levels of drug resistance among disease-causing microbes. In 2014 an independent report commissioned by the UK Government said that superbugs could kill an extra 10 million people a year and cost up to $100 trillion globally by 2050 if not brought under control.
Together with a team of French scientists, Vittecoq searched the literature for studies on antimicrobial resistance in wildlife. They found only 210 peer-reviewed papers, revealing worrying gaps in our knowledge as well as some key lessons.
Most studies focussed on birds and mammals in Europe and North America, with very little data on developing countries or insects, and concerned only three groups of bacteria, the human pathogens Escherichia coli, Salmonella spp and Enterococcus spp.
We need research on a wider range of bacteria and host species because of the complex ways in which bacteria can develop and exchange resistance mechanisms, Vittecoq says: "Antimicrobial resistance mechanisms that may impair our ability to treat severe diseases may be carried and spread by a wide range of bacteria groups including non-pathogenic ones. If we only focus on human pathogens when we search for resistance in bacteria carried by wildlife then we won't get a comprehensive view of the mechanisms present in a habitat."
The study makes several key recommendations. It reveals that water plays a major role in the exchange of superbugs between wildlife, humans and domestic animals, and aquaculture and sewage works are key routes by which aquatic environments can be contaminated by antimicrobial drugs and antimicrobial resistant bacteria.
"Limiting water contamination may be key to controlling the spread of antimicrobial resistance in natural ecosystems, so a first important step could be to limit water contamination through the development of improved wastewater treatment," she says.
The study found that superbugs are most common, and most diverse, in environments that are most affected by human activities, and that omnivorous and carnivorous species of wildlife are most likely to carry and spread superbugs.
As a result, the study recommends more research on the potential spread of superbugs, for example by taking advantage of hunting to get samples from game species, and multidisciplinary studies that focus in parallel on humans, cattle and wildlife to get a better understanding of the whole system in which antimicrobial resistance mechanisms are exchanged.
It also advocates the 'One Health' approach, a concept that views human, animal and ecosystem health as interconnected and which has been successfully used in studies of viruses such as influenza and SARS.
"If we control antimicrobial resistance spread within human and cattle populations but are not interested in limiting the contamination of natural habitats by antimicrobial drugs, those areas may become reservoirs of antimicrobial resistance mechanisms that may remain there even when they have (hopefully) been eliminated from hospitals and farms," Vittecoq concludes.
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