Lucas Alonso, researcher at the University de la Plata in Argentina, headed an unpublished work for Latin America last year. Together with a group of researchers, he showed that antibiotics are found as pollutants in rivers and streams of the Cuenca del Plata, one of the largest drainage basins in the world. Here he replies to a few questions on the subject.
Lucas, why are antibiotics used in food animal production?
Many times, antibiotics are used in animal production as part of a generalized production model. This model begins by confining animals to spaces where there are bad hygiene conditions. This creates an environment where diseases spread easily, because animals are surrounded by their own urine and their own feces. It is in this scenario that antibiotics enter. These drugs are administered preventively to stop spread of infections through mixing it with the feed (medicated feed) of the animal or in the drinking fountains.
Some microbes that are found in the animals’ digestive systems are susceptible to these antibiotics, which changes the way they process the food that they consume and they grow faster. The animals are subjected to a food containing antibiotics not for therapeutic reasons but to prevent infections and to make the animals grow faster.
Lucas Alonso holds a Doctoral Fellow position at the Centre for Environmental Research (CIM, Argentina) and works as a University teacher and researcher at National of La Plata in Argentina.
He has conducted investigations on the contamination of waters by residues from agricultural activity.
How and why do antibiotics get into the ecosystems?
There is a change in the concept of antibiotics from when it is given to the animals to when it enters the environment. A part of the antibiotics given to animals is excreted through urine and feces, and is conceptually transformed into a pollutant, because it becomes a substance that is in a place that should not to be and can generate harm. We no longer have control of it because it integrates into the environment.
Production systems accumulate large amounts of excreta (feces and urine), which is used as manure. Antibiotics can be transported to water through rain that washes over the manure, and the antibiotic residues from the manure can be mobilized to water sources nearby.
Manure is a waste of great value for agriculture due to the content of organic matter and nutrients, such as phosphorous and nitrogen and is mainly used in horticulture.
At a first glance, manure is a very good input because it replaces the use of synthetic fertilizers. But what happens is that it comes loaded with antibiotics because it was generated in a process where animals received these antibiotics routinely, and we are now transferring the antibiotics to the soils where we produce vegetables and fruits.
There are several consequences that can arise, like sometimes being available in the ground and sometimes being captured by plants as if it were a nutrient being able to enter the plant generating some effect like accumulating and if after that plant is consumed we can ingest those antibiotics that they are on the ground.
In addition, since the function of an antibiotic is to eliminate bacteria, it may be that when we spread this manure contaminated with antibiotics, we are negatively affecting the microbiome of the soil. All the beneficial microorganisms of the soil can suffer adverse effects and we would be reducing the fertility of that soil because bacteria and microorganisms are part of what gives it life and improve the quality of those soils.
So it is necessary to be very careful and know the origin of the manure since we must avoid transferring the problems we have in the breeding sites to cultivated soils.
What happens when antibiotics reach the environment?
Antibiotics, like any other molecule, have physical-chemical properties that define where they could spread once they reach the environment. Once they enter a body of water, they can stay in the sediments or move with the water.
According to a study carried out by our team of researchers, antibiotics were shown to be transported in the water and taking the problem to other places. For example, antibiotic concentrations are high in bodies of water nearby places where animals are raised for human consumption, and disperse downstream. They do not degrade easily, causing long-term effects on ecosystems.
What are the security risks for food bacterial resistance?
As such, food security does not only include making food healthy but also ensuring your production is sustainable. On the one hand, the use of antibiotics routinely in raising animals for human consumption, can also generate accumulation and generate contamination in food that is consumed and in the soils that serve for the production of fruits, vegetables and cereals. This can put the quality of the food we have at risk, precisely due to the incorporation of antibiotics. On the other hand, food security has to consider the damage to the environment that is caused by production processes, so it is important to regulate antibiotics.
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