EIn the name of healthy eating habits, the consumption of fish has been increasingly recommended to replace red meat, among other reasons, because it has a lower amount of fat and because it contains omega 3, a very active antioxidant in the fight against cardiovascular diseases. However, in relation to food safety, fish meat, like other foods of animal origin, may contain residues of veterinary medicines, including antibiotics. This is what studies carried out at the Chemistry Institute (IQ) at Unicamp show.

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for others species

Aquaculture, understood as the cultivation of aquatic organisms, is the fastest growing food production system of animal origin in the world, especially in developing countries. Brazil has great potential in this activity given the vastness of the territory, privileged by rich river basins – with emphasis on the Amazon region, responsible for 20% of the Earth's fresh water – and a coastline of more than eight thousand kilometers.

In aquaculture in general and fish farming in particular, captive breeding is used, which has made the use of antimicrobials – antibiotics – imperative for the producer to guarantee their production and not run the risk of losses, as infectious diseases constitute potential risks. . However, in Brazil there is no legislation that regulates the use of veterinary medicines in aquaculture, which leads to their misuse. Producers, most of the time, use formulations indicated for other species, compromising medication prescriptions such as dosage, treatment period and withdrawal period, fundamental indications to guarantee the complete action of the medication and its elimination, so that residues in meat are at concentrations below the limits considered safe and recommended by health bodies.

This fact raises two main issues: food safety and bacterial resistance. The misuse of antibiotics can result in products intended for consumers with residues at levels that can compromise health. Furthermore, at the production site, they favor the selection of resistant bacteria, which can compromise the environment and even the consumer, due to the reduction in the efficiency of the medicines.

This situation motivated agricultural engineer Jonas AR Paschoal to develop a doctorate in the area of ​​determining antibiotic residues in fish meat. The researcher also carried out a test with tilapia, one of the main species of fish produced in the world, to evaluate oxytetracycline residues in the meat of these animals in periods after medication, in order to evaluate what is called residual depletion. It is established through a curve that shows how the concentration of residues of the substance in the meat decreases after medication.

Oxytetracycline is a widespread product, relatively cheap, recommended for practically all animal species, widely used because it is easily found on the market, has a broad spectrum of action and is efficient for its purpose, which is why it was chosen.

When comparing the results obtained with those reported in the literature, the researcher concludes that there is a need for studies in the national territory to be carried out in the fish farming region, aiming to establish grace periods, since the depletion parameters depend not only on the animal species, but also environmental conditions, more particularly the temperature of the environment.

According to Jonas Paschoal, the work addresses two important issues. The first deals with the development of analytical methodologies for analyzing fish meat available on the market or even in production tanks, which allow determining the residue rates present and evaluating the use of antibiotics. The second brings to light the dependence of metabolism on the breeding environment. The so-called withdrawal period for the drug to act – the period that the producer must wait to slaughter the animal after medication – must be determined through residual depletion tests and pharmacokinetic studies, which allow the evaluation of the absorption and elimination of the drug.

He states that the resulting doctoral thesis contributes to highlighting the importance of these types of information and serves as guidance for other research that can and should be carried out. He emphasizes that the legislation that regulates the use of veterinary medicines in aquaculture must be based on scientific studies carried out in the climate and handling conditions that permeate national production. On the other hand, the establishment of control analyzes of commercialized products requires reliable methods, such as those used and described in the thesis.

As in Brazil there are no antimicrobials specifically legislated for application in aquaculture that can be used in the farming of shrimp, molluscs and fish, producers use regulated medicines intended for cattle, goats, pigs and other livestock.

Professor Susane Rath, research advisor, considers that this fact, aggravated by veterinary practices that are not always correct, leads to consequences that are much more serious than the residue of the antimicrobial that remains in the meat and could be harmful to health. For her, the big discussion that arises today is the progressive increase in bacterial resistance that manifests itself at the production site, leading to the development of resistant bacteria, which can affect humans.

“I am not against the use of antibiotics, which are recognized as necessary in confined farms, but their application must respect good veterinary practices that prescribe appropriate uses. Furthermore, resistant bacteria that develop in the breeding environment can create problems for the production system itself and, more seriously, end up affecting the ecosystem”, warns the researcher.

Work involving antibiotic residues. have a long history at Unicamp with the Food and Drug Toxicology Group (GTAF), coordinated by professors Susanne Rath (IQ) and Felix GR Reyes (FEA), who has already carried out studies on chicken meat, milk, honey, tomatoes. Jonas Paschoal approached Professor Susanne interested in developing analytical methods to detect antibiotic residues in foods of animal origin.

He ended up choosing to do it in fish farming and explains: “It is the fastest growing food production system in the world, and Brazil is one of the countries with the greatest potential for exploring this activity”. Professor Susane adds that “if the country intends to explore and expand this type of activity with a view to the international market, it is necessary that this type of research is urgently implemented, so that problems similar to those that led to the recent shipment of beef into the European Community”.

The researchers clarify that, although the Ministry of Agriculture, Livestock and Supply maintains the National Plan for Control of Residues in Products of Animal Origin (PNCR), aimed at controlling pesticides and veterinary medicines in meat, milk, honey and fish, the plan does not provide for the control of tetracyclines and quinolones in fish.

In turn, the National Program for the Analysis of Veterinary Drug Residues in Food Exposed to Consumption (PAMVet) is still in the implementation phase of analyzing milk samples only. The paradox, they say, is that, although there is no legislation that regulates the use of antibiotics in aquaculture, ordinances indicate, based on international standards, the residue levels that must be respected, even if the products sold are not controlled, a situation which has become routine in the country.