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Microplastics might transfer pathogens to farmed seafood

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The role that microplastics play in transporting bacteria and viruses is unclear but researchers have expressed concern that they could be affecting the health of humans and animals exposed to them.

The world has a growing plastic waste problem with trillions of microplastic particles floating in the ocean that are known to carry specific combinations of metals, pollutants and pathogens.

A new study by the University of Exeter and the Centre for Environment, Fisheries and Aquaculture Science (Cefas) is assessing whether microplastics pose a possible threat to food production and safety.

Seafood farming, which already faces challenges due to diseases, is vulnerable to the issue and it is expected to play a vital role in feeding the world’s growing population in the future.

“Microplastic fragments differ markedly from natural floating particles, and there is growing evidence that they represent a potential reservoir of pathogens,” said Dr Ceri Lewis, of Exeter’s Global Systems Institute.

“Of particular concern are the increasing reports of the presence of numerous pathogens on plastic surfaces in oceans around the world.

“One study found antimicrobial-resistant bacteria at concentrations 100-5,000 times higher on microplastic surfaces than in surrounding seawater.

“However, the effects of all this on marine animals, aquaculture and ultimately human health are really unknown at this point.”

Many studies have suggested that disease transfer from plastic to ingesting organisms may occur, but this has not been demonstrated experimentally.

Aquaculture is now the fastest-growing food sector, and bivalves (such as mussels and oysters) arguably offer the best route to increase production globally.

However, bivalves are filter-feeders and are known to take in microplastic particles from seawater.

“Understanding any risk of pathogen transport associated with microplastic is important for the aquaculture industry,” said lead author Jake Bowley, of the University of Exeter.

“Disease is one of the biggest issues faced by the industry.

“We mapped the abundance of sea-surface plastics against areas of intensive aquaculture, and the results show a number of areas of high aquaculture production in microplastic hotspots where pathogen transfer could theoretically occur.

“One such hotspot is in China, where 57 microplastic particles per individual have been reported in the commercially important Yesso clam.”

Dr Craig Baker-Austin, of Cefas, added: “Bacteria from a genus called vibrio - a globally important group of human and animal pathogens that are increasing in incidence - have been found in high levels on microplastics.

“Some vibrio bacteria are known to contribute to disease in bivalves, often causing mass mortality among larvae and in some cases mortality within adult bivalve populations.”

Earlier this month, another team at the University found that devices to clean up ocean surface plastic pollution are not effective enough to deal with the broader problem.  

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