A new report has issued an urgent warning on the spread of drug resistance (anti-microbial resistance, AMR) from animal to human pathogens. It identifies aquaculture as a major source worldwide. Aquaculture (fish farming) is an under-appreciated source of AMR, and as global citizens we can no longer neglect its ecological and human impacts.
The challenge for the scientific and political community is to find a sustainable solution to the spread of AMR without compromising the economic security of fishing societies.
As with so many other health and environmental disasters, coastal communities in low- and middle-income countries in Africa and South Asia are facing the worst of this crisis. Rates of AMR in humans are skyrocketing in places that do not have the infrastructure or resources needed to monitor the spread of resistance in hospitals, a measure thought to be key in controlling AMR outbreaks.
We have been building to this moment for a long time. For decades, fishing communities have made heavy use of antibiotics to boost animal growth and to prevent disease outbreaks. Intensification of aquaculture has meant ever-increasing numbers of fish are kept in pens and ponds, in some cases devastating aquatic ecosystems. Take for example Saprolegnia parasitica, a fungal-like organism from the oomycete family. This species is naturally saprotrophic it eats dead things, contributing to the carbon cycle. But when salmon are farmed intensively, packed together in crowded pools, S. parasitica becomes a deadly parasite, necrotizing the flesh of stressed animals and causing the disease Saprolegniasis.
From an animal welfare point of view, infections like these seem avoidable the disease stems directly from animal over-crowding, so a simple solution would be to keep fewer fish together or give them more space. But this would reduce yields at a time when farmed fish are vital to feed our growing global human population. And it neglects the central role of aquaculture in supporting the economies of coastal communities, particularly in low- and middle-income countries.
Fish farming can be an economic boon, but it comes with risks. Vulnerability to climate change and local spread of AMR in human pathogens are directly correlated. There is even evidence that increasing water temperatures due to climate change increases the severity of some fish diseases, which will almost certainly lead to ever-greater reliance on antibiotics as the oceans continue to heat.
Of course, the global economic importance of aquaculture means that lots of well-funded research is going on, developing new drugs and vaccines to control pathogens and prevent infection. Farmed salmon have been vaccinated against furunculosis in Norway since the 1980s, where the use of antibiotics on fish farms is now minimal. Other northern European countries are looking at new offshore systems for fish farming that use recirculation aquaculture in indoor tanks to prevent runoff of pharmaceuticals into the wider ocean.
2017 2019 Massive Science Inc.