publicado em 29/03/2012 às 14h36:00
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Oysters can accumulate disease-causing agents, proves research

Survey also revealed that molluscs from breeding sites of oysters also contained virus

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The Pacific oyster feeds on plankton by sucking and filtering the sea water.
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The Pacific oyster feeds on plankton by sucking and filtering the sea water.

A group of Brazilian researchers assessed the impacts of different degrees of pollution in the creation of the Pacific oyster in Florianópolis, capital of Santa Catarina, responsible for 95% of the shellfish production in Brazil. In search of a diagnosis of the condition of animals sold, the study published in February in Ecotoxicology and Environmental Safety confirmed that oysters can accumulate in your body chemicals and agents such as viruses, bacteria and protozoa that cause disease in people. These organisms can cause infections, especially in those who eat raw food. The survey also showed that snails from breeding sites of oysters contained virus even when the cultivation sites had acceptable levels of fecal coliform, according to a resolution of the National Environment Council (CONAMA). Critical situations were found in animals experimentally placed in the most polluted environments, not used as breeding sites.

The oyster (Crassostrea gigas) feeds on plankton that live adrift at sea, and does so by sucking and filtering the water. In the food itself, it absorbs and other chemicals are organic in water to be killed or become infected with these viruses, bacteria and protozoa. They are retained in the tissue of the animal, protected from abuse and ultraviolet radiation from the sun, says the study coordinator Monte Barardi Regina Célia, the Virology Laboratory, Department of Applied Microbiology, Immunology and Parasitology, Federal University of Santa Catarina (UFSC) . Oysters can accumulate metals, pesticides and other organic compounds in their tissues and gills, reaching higher concentrations than those present in seawater. Therefore, the quality of shellfish sold is related to sanitary conditions in the waters where they are grown.

The study was conducted in partnership with the Center for Research on Aquaculture Pathology and Center for Agricultural Sciences and Laboratory for Biomarkers of Aquatic Contamination (both from UFSC), Marine Organic Chemistry Laboratory, University of São Paulo (USP) and Laboratory of Protozoology State University of Campinas (Unicamp). The researchers inserted oysters from the Lab Cultivation of Marine Molluscs (UFSC), located on Shellmound (see map) in four locations: Ribeirão da Ilha (number 1 on map) and Santo Antonio de Lisboa (2), where there is currently growing shellfish; Tapera (3), with cultivation disabled due to the proximity of the coast and heavy traffic of boats, which cause contamination of the sea, and river mouth BÜCHELER (4), unsuitable for cultivation for receiving domestic sewage.

The sea water and pellets were analyzed at the time when the left researchers oysters and 14 days later when collected. The team found through analysis of microbiological contamination of shellfish by viruses that attack humans, organic compounds, protozoa and bacteria such as fecal coliforms, eliminated through the feces and urine of people, besides heavy metals, petroleum products and pesticides dumped at sea.

As expected, the oysters collected from the river mouth BÜCHELER, the most polluted of the four sites studied, contained a greater number of human pathogens: adenovirus (which can cause respiratory infection, conjunctivitis or gastroenteritis), norovirus (the leading cause of nonbacterial acute gastroenteritis), hepatitis A virus, polyomavirus (dangerous for people with low immunity) and fecal coliforms. Pesticides, hydrocarbons and steroids were also found in the oysters taken from near the river BÜCHELER. Already collected in the old area of ​​cultivation Tapera contained norovirus, fecal coliforms and protozoa Cryptosporidium spp., Which can cause intestinal problems.

Oysters collected in two areas currently used for cultivation, Ribeirão da Ilha and Santo Antonio de Lisboa, had fewer triggers of disease compared to other regions analyzed. However, as they filter seawater, shellfish from these areas are still at risk of possible contamination. This is because both locations are subject to receiving the input of domestic sewage, rural, urban and treated and untreated pollutants such as petroleum.

A solution for those who would like the molluscs to ingest the cooked food may be in the exhalation (steam) at a temperature exceeding 90 ° C. This action inactivates viruses, protozoa and fecal coliforms, the researcher explains. However, does not eliminate pesticides or heavy metals.

Another way to protect people from contamination by microorganisms, pesticides or heavy metals would cultivate oysters in clean water, says Celia. In order to reduce the risk of contamination by microorganisms that cause disease, researchers at UFSC, among them one of the authors Doris Marques Souza Sobral, debuggers are testing small-shaped tanks. The water of these scrubbers is sterilized with ultraviolet light. As the oyster feeds by filtering water, we expect to remain clam in the tanks with sea water purified by ultraviolet radiation, decrease the amount of contaminants retained by oysters, says the researcher. The idea is to install equipment in restaurants and establishments that sell the shellfish.

Source: FAPESP
   Palavras-chave:   Oyster    Infection    Transmission    Pollution    FAPESP    Foundation for Research    National Council on the Environment    CONAMA   
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