Microplastics – tiny particles produced as plastic weathers and fragments – pose a growing threat to ecosystems and human health. These threats go beyond direct physical or chemical effects, a new laboratory study suggests that the presence of microplastics increases the severity of an important viral fish disease.
lead author on the study, published in Science of the Total Environment, Dr. Meredith Evans Seeley, who conducted the research as part of her Ph.D. program at the Virginia Institute of Marine Science of William & Mary. Joining him as co-authors were VIMS professors Rob Hale, Andrew Wargo and Wolfgang Vogelbein; W&M Professor Patty Zvolo; and VIMS laboratory technician Galen Verey.
“Microplastics and pathogens are everywhere,” Seeley says, “but they are often present in highest concentrations in densely populated aquatic environments such as fish farms. We wanted to find out whether microplastics affect the severity of IHNV infection in aquaculture.” can affect.” IHNV is a virulent pathogen in salmonid aquaculture, affecting members of the salmon family including rainbow trout, steelhead trout, chinook salmon, and sockeye salmon.
The team wanted to determine whether there could be a “cause and effect” between microplastics, viruses and fish mortality. Seale and his colleagues exposed aquarium-housed rainbow trout to low, medium and high concentrations of three different types of microparticles, and then added the IHN virus to half the tanks. They selected plastics that are widely used in aquaculture and commonly found in nature as breakdown products: polystyrene foam (often in floats, buoys, home insulation and food containers); and nylon fibers (lost from fishing nets, fishing line, and clothing). They also exposed infected and healthy fish to small pieces of common saltmarsh cordgrass. Spartina alterniflora, There were no viruses or microscopic particles in the control tanks.
their results? “We found that co-exposure to microplastics and viruses increased disease severity,” says Seale, “with nylon fibers having the biggest effect.” This is the first time this interaction has been documented, and emphasizes the importance of testing multiple stressors, which is more environmentally realistic.”
Dr. Rob Hale, an environmental chemist and Sealy’s doctoral advisor at VIMS, agrees. “Our results,” he says, “show that we should consider the toxicity of microplastics not alone but in combination with other environmental stressors.”
Dr Andrew Wargo, an expert in the ecology of infectious diseases, says that IHNV is a worldwide issue. “It originated in the Pacific Northwest, where it is causing major problems for both salmonid aquaculture and conservation. Our study shows that there is an interaction between microplastics and IHNV. We don’t yet know if aquaculture How this interaction plays out in human or wild environments will ultimately depend on the amount of plastic pollution and IHNV in any given area.”
Not all microparticles are created equal
Based on their laboratory results, the researchers suspect that exposure to microparticles increases disease severity by physically damaging the delicate tissue lining the gills and gut, making it easier for the virus to colonize its host. goes.
Exposure to synthetic microplastics – nylon and polystyrene – had a greater effect than natural microparticles spartina, Exposure to nylon-derived microfibers had the greatest effect. The researchers suspect that this may be due to their larger size, extended length, or greater rigidity of the plastic compared to plant matter.
“Nylon microfibers are larger and may be more likely to get stuck and damage the delicate tissues of the lining of the gills and gut,” says Seeley. “This may make it easier for the virus to enter and exert pressure on the host, ultimately leading to an increase in disease virulence.”
The team’s work has major implications beyond fisheries. “Our research question is very relevant in aquaculture,” says Seeley, “but it also applies to natural environments. Microplastics are distributed around the world, so at any given time they co-occur with a variety of natural pathogens.” Can.”
“Disease and microplastics can interact to produce poor consequences in a range of aquatic and terrestrial systems,” says Hale, “including wild fish, corals, and birds.” If you test for microplastics alone you may not see any effect and call it a day, but in the real world they can interact with microplastic pathogens, increasing temperatures, decreasing pH, increasing water turbidity and other variables Huh.”
Sealy says the team’s results may also be relevant to human health. “Indoor environments are dense with microplastics – for example in household dust,” she says. “This leads us to wonder how indoor microplastic contaminants might affect the progression of airborne diseases such as COVID-19.”