The migrating shorebird called the “Straight-billed Curlew” (Limosa haemastica), travels every year 15 thousand kilometers from the coastal wetlands of Chiloé to Alaska to spend its reproductive season in the northern hemisphere.

To carry out this trip, he must carry out a preparation that includes physiological adaptations that allow him to fly for seven consecutive days to the wetlands of the great plains of North America, his only stopover at 10,000 kilometers from Chiloé.

Among these adaptations, this bird doubles its weight and reduces the size and functionality of organs that are not essential for its flight, such as the stomach and liver, while those that serve them for movement increase in volume.

However, the presence of antibiotics in the bays, the places where the Curlew and other species find their food, could alter their ability to complete all these adaptations in time to migrate.

In this context, experts in marine biology and ecology raised the need to measure which of these compounds are present in the environment and organism of this species.

The work was led by Juan Navedo, head of the Bird Ecology Lab of the Institute of Marine and Limnological Sciences, and director of the Quempillén Experimental Station of the Faculty of Sciences of the Austral University in Chiloé, under the auspices of the FONDECYT project.

” Assessing sub-lethal pollution effects on wildlife: prevalence of antibiotic resistance in coastal environments and associated costs to migratory birds ”.

In this study, developed in conjunction with Claudio Verdugo, a researcher at the Faculty of Veterinary Sciences of the Austral University, and Valeria Araya, a Ph.D. student in Marine Biology at the same institution, the presence of resistant bacteria and genes of Resistance to different antibiotics in coastal wetland sediments and in the intestinal microbiota of Curlew birds.

For this, two bays in Chiloé were investigated; the first to the north in the Chacao channel, 30 km from the nearest marine culture center; and the second next to the Dalcahue canal, surrounded by marine farming centers.

The first results of this research were published in 2021 in the prestigious journal Science of the Total Environment under the title (Translated) “Raising a silent pollution: resistance to antibiotics in coastal environments and transfer to long-distance migratory shorebirds.”

The antibiotic footprint and the visibility of the effects of these drugs on the environment
As is well known, the marine phase of salmon farming takes place in cages with high fish densities, where the salmon are fed to the desired size.

There, along with the food, they are given drugs for the treatment of different diseases, some of them bacterial origin such as Piscirickettsia salmonis.

“Seven antibiotics from different families were studied, three of them used exclusively in the salmon industry,” explained Navedo, academic of the Doctorate in Marine Biology and Doctorate in Ecology and Evolution of the Faculty of Sciences of the Austral University of Chile.

The results obtained showed that 62% of the sediment samples, considering both bays, had resistant bacteria and genes for resistance to at least one antibiotic, while only the area closest to the farming centers were found multi-resistant bacteria.

Furthermore, 87% of the samples from the poultry sewers presented bacteria resistant to at least one antibiotic, 63% being multi-resistant, and some of them with a high potential for pathogenicity. Finally, regarding the resistance genes, these were present in 46% of the bird samples, being multiresistant in many cases.

The data of this study have been a concrete contribution to the visibility of the effects of these drugs in the environment and have been widely shared with the scientific community, for example, through the letter recently published in the journal Science (translated) “Salmon aquaculture threatens Patagonia”.

In it, Navedo together with Luis Vargas-Chacoff, also an academic of the Doctorate in Marine Biology at the Austral University of Chile, make a direct call to the Government of Chile to increase the regulations for this industry, while at the international level they suggest pressing for improve environmental policies in our country and thus stop the salmon expansion.

Currently, together with other researchers and doctoral students from the Bird Ecology Lab, Dr. Navedo is finishing assembling several experiments already carried out, to also know if environmental exposure to antibiotics (non-clinical doses) has effects on any biological process Curlew life, which would have implications for other vertebrates, including humans.

“In an experimental and environmental approach, we are observing how these components may have modified the composition of the intestinal microbiota in vertebrates, since an imbalance in this bacterial community could cause dysfunctions in vital processes, such as the absorption of nutrients or the immune capacity. ”, He detailed.

Although the conclusions of these experiments have not yet been published, the researcher highlights that it is essential to make transparent what is the load of antibiotic residues that passes from the culture cages to nature, considering that according to the 2020 Report on the use of antimicrobials in the national salmon farming of the National Fisheries and Aquaculture Service, last year a total of 379 tons of antibiotics were used, reaching an annual harvest of one million 75 tons of salmon.

“To produce a kilo of salmon in Chile 100 times more antibiotics are used than in Norway, which is the world’s leading producer of this product. This volume of medicines reinforces the idea that the antibiotic footprint should be widely spread on the coasts of southern Chile and can even reach North America through migratory birds, affecting multiple components of biodiversity, including being human ”, emphasized the academic.

Finally, he added, it is increasingly urgent in the global context of ‘One health’ to reduce the densities of salmon farming and the planning of the cage capacity that may exist in each area, since this will allow to limit the potential incidence of disease and the volume of antibiotics used in the industry.

By ritu

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