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Miami Herald
4 days ago
- Health
- Miami Herald
California freshwater fish found to be teeming with parasites. How to keep from getting sick
LOS ANGELES - More than 90% of popular freshwater fish in Southern California are carrying human-infecting parasites, researchers say. This poses a significant danger for those who like to eat freshly caught freshwater fish. But there are ways to protect yourself. The parasites are called trematodes. Two species of the flatworms were discovered in California's freshwater fish, according to a study published Tuesday in the Journal of Infectious Diseases. The tiny, flattened and sluglike creatures can cause gastrointestinal problems, weight loss and lethargy when a person eats an infected fish. In some rare and severe cases, the parasites have caused strokes or heart attacks. "Americans don't usually think about parasites when they eat freshwater fish because it hasn't historically been an issue here," said Ryan Hechinger, the study's senior author. In fact, even when a person has fallen ill from a locally caught infected freshwater fish, their healthcare provider will typically ask if the patient has recently traveled outside of the United States, Hechinger said. California wasn't this parasite's first home Researchers identified two species of trematode: Haplorchis pumilio and Centrocestus formosanus. These two parasite species have historically infected people in Southeast Asia who eat raw fish, crustaceans or vegetables that carry the parasite larvae. A trematode has a very specific life cycle, leeching onto three hosts that include a freshwater snail, a fish and then a bird or human who ate the infected fish. The parasite was probably carried to the U.S. by the red-rimmed melania, or Malaysian trumpet snail, which is host to a number of parasitic species and was introduced to the United States, Hechinger estimates, decades ago. It inhabits "freshwater springs, streams, lakes and swamps," according to the Smithsonian Environmental Research Center, but can occasionally be found in "brackish and marine habitats, especially mangroves" (think the Everglades). The snail first popped up in California in 1972 in a Riverside County ditch, according to the center. Hechinger, through previous and new research, found that the snail and its associated trematode parasites can be widely found in lakes and reservoirs across the state. He's identified the snails in Los Angeles, Imperial, Orange, Riverside, San Bernardino and San Diego counties. Some fish harbor thousands of parasites In summer and fall 2023, researchers, with the help of the California Department of Fish and Wildlife, analyzed fresh fish that were collected at five fishing localities in San Diego County: Miramar, Murray, Lower Otay and San Vicente reservoirs as well as Chollas Lake. The fish included largemouth bass and bluegill. Hechinger and his team found that 93% of all the fish in the study were infected with the H. pumilio parasite, with some individual fish harboring thousands of the parasites. The second parasite, C. formosanus, was found at two of the five locations, where it occurred in 91% of the fish. The parasites are each found on different parts of the fish. H. pumilio is found at the base of the fins and C. formosanus is found on the gills. But the parasites can infect the muscles and connective tissue of the fish, Hechinger said, which is how a person eating it can get sick despite cutting off the head and fins. "The other thing we have to remember," he said, "is the possibility of contamination on the food preparation surfaces and utensils." How to protect yourself The risk is real, but the precautions you can take against illness are straightforward. Thorough cooking of any freshwater fish that could potentially be infected can prevent illness, according to the U.S. Food and Drug Administration. If you choose to eat the fish raw, the agency advises you eat freshwater fish that has been previously frozen. Freezing will kill parasites that may be present. However, the FDA said freezing doesn't kill all harmful germs, so the safest route is to thoroughly cook your seafood. Some food prep is fishy As part of this study, researchers conducted a survey of 125 YouTube videos with a total of 5 million views and found that 65% of these videos did not mention proper cooking or freezing of caught fish. The lack of proper food preparation not only promotes the transmission of parasites but can also increase the odds of infection, Hechinger said. Copyright (C) 2025, Tribune Content Agency, LLC. Portions copyrighted by the respective providers.
Yahoo
4 days ago
- Health
- Yahoo
California freshwater fish found to be teeming with parasites. How to keep from getting sick
More than 90% of popular freshwater fish in Southern California are carrying human-infecting parasites, researchers say. This poses a significant danger for those who like to eat freshly caught freshwater fish. But there are ways to protect yourself. The parasites are called trematodes. Two species of the flatworms were discovered in California's freshwater fish, according to a study published Tuesday in the Journal of Infectious Diseases. The tiny, flattened and sluglike creatures can cause gastrointestinal problems, weight loss and lethargy when a person eats an infected fish. In some rare and severe cases, the parasites have caused strokes or heart attacks. 'Americans don't usually think about parasites when they eat freshwater fish because it hasn't historically been an issue here,' said Ryan Hechinger, the study's senior author. In fact, even when a person has fallen ill from a locally caught infected freshwater fish, their healthcare provider will typically ask if the patient has recently traveled outside of the United States, Hechinger said. Researchers identified two species of trematode: Haplorchis pumilio and Centrocestus formosanus. These two parasite species have historically infected people in Southeast Asia who eat raw fish, crustaceans or vegetables that carry the parasite larvae. A trematode has a very specific life cycle, leeching onto three hosts that include a freshwater snail, a fish and then a bird or human who ate the infected fish. The parasite was probably carried to the U.S. by the red-rimmed melania, or Malaysian trumpet snail, which is host to a number of parasitic species and was introduced to the United States, Hechinger estimates, decades ago. It inhabits "freshwater springs, streams, lakes and swamps," according to the Smithsonian Environmental Research Center, but can occasionally be found in "brackish and marine habitats, especially mangroves" (think the Everglades). The snail first popped up in California in 1972 in a Riverside County ditch, according to the center. Hechinger, through previous and new research, found that the snail and its associated trematode parasites can be widely found in lakes and reservoirs across the state. He's identified the snails in Los Angeles, Imperial, Orange, Riverside, San Bernardino and San Diego counties. In summer and fall 2023, researchers, with the help of the California Department of Fish and Wildlife, analyzed fresh fish that were collected at five fishing localities in San Diego County: Miramar, Murray, Lower Otay and San Vicente reservoirs as well as Chollas Lake. The fish included largemouth bass and bluegill. Hechinger and his team found that 93% of all the fish in the study were infected with the H. pumilio parasite, with some individual fish harboring thousands of the parasites. The second parasite, C. formosanus, was found at two of the five locations, where it occurred in 91% of the fish. The parasites are each found on different parts of the fish. H. pumilio is found at the base of the fins and C. formosanus is found on the gills. But the parasites can infect the muscles and connective tissue of the fish, Hechinger said, which is how a person eating it can get sick despite cutting off the head and fins. "The other thing we have to remember," he said, "is the possibility of contamination on the food preparation surfaces and utensils." The risk is real, but the precautions you can take against illness are straightforward. Thorough cooking of any freshwater fish that could potentially be infected can prevent illness, according to the U.S. Food and Drug Administration. If you choose to eat the fish raw, the agency advises you eat freshwater fish that has been previously frozen. Freezing will kill parasites that may be present. However, the FDA said freezing doesn't kill all harmful germs, so the safest route is to thoroughly cook your seafood. As part of this study, researchers conducted a survey of 125 YouTube videos with a total of 5 million views and found that 65% of these videos did not mention proper cooking or freezing of caught fish. The lack of proper food preparation not only promotes the transmission of parasites but can also increase the odds of infection, Hechinger said. Sign up for Essential California for news, features and recommendations from the L.A. Times and beyond in your inbox six days a week. This story originally appeared in Los Angeles Times.
Los Angeles Times
5 days ago
- Health
- Los Angeles Times
California freshwater fish found to be teeming with parasites. How to keep from getting sick
More than 90% of popular freshwater fish in Southern California are carrying human-infecting parasites, researchers say. This poses a significant danger for those who like to eat freshly caught freshwater fish. But there are ways to protect yourself. The parasites are called trematodes. Two species of the flatworms were discovered in California's freshwater fish, according to a study published Tuesday in the Journal of Infectious Diseases. The tiny, flattened and sluglike creatures can cause gastrointestinal problems, weight loss and lethargy when a person eats an infected fish. In some rare and severe cases, the parasites have caused strokes or heart attacks. 'Americans don't usually think about parasites when they eat freshwater fish because it hasn't historically been an issue here,' said Ryan Hechinger, the study's senior author. In fact, even when a person has fallen ill from a locally caught infected freshwater fish, their healthcare provider will typically ask if the patient has recently traveled outside of the United States, Hechinger said. Researchers identified two species of trematode: Haplorchis pumilio and Centrocestus formosanus. These two parasite species have historically infected people in Southeast Asia who eat raw fish, crustaceans or vegetables that carry the parasite larvae. A trematode has a very specific life cycle, leeching onto three hosts that include a freshwater snail, a fish and then a bird or human who ate the infected fish. The parasite was probably carried to the U.S. by the red-rimmed melania, or Malaysian trumpet snail, which is host to a number of parasitic species and was introduced to the United States, Hechinger estimates, decades ago. It inhabits 'freshwater springs, streams, lakes and swamps,' according to the Smithsonian Environmental Research Center, but can occasionally be found in 'brackish and marine habitats, especially mangroves' (think the Everglades). The snail first popped up in California in 1972 in a Riverside County ditch, according to the center. Hechinger, through previous and new research, found that the snail and its associated trematode parasites can be widely found in lakes and reservoirs across the state. He's identified the snails in Los Angeles, Imperial, Orange, Riverside, San Bernardino and San Diego counties. In summer and fall 2023, researchers, with the help of the California Department of Fish and Wildlife, analyzed fresh fish that were collected at five fishing localities in San Diego County: Miramar, Murray, Lower Otay and San Vicente reservoirs as well as Chollas Lake. The fish included largemouth bass and bluegill. Hechinger and his team found that 93% of all the fish in the study were infected with the H. pumilio parasite, with some individual fish harboring thousands of the parasites. The second parasite, C. formosanus, was found at two of the five locations, where it occurred in 91% of the fish. The parasites are each found on different parts of the fish. H. pumilio is found at the base of the fins and C. formosanus is found on the gills. But the parasites can infect the muscles and connective tissue of the fish, Hechinger said, which is how a person eating it can get sick despite cutting off the head and fins. 'The other thing we have to remember,' he said, 'is the possibility of contamination on the food preparation surfaces and utensils.' The risk is real, but the precautions you can take against illness are straightforward. Thorough cooking of any freshwater fish that could potentially be infected can prevent illness, according to the U.S. Food and Drug Administration. If you choose to eat the fish raw, the agency advises you eat freshwater fish that has been previously frozen. Freezing will kill parasites that may be present. However, the FDA said freezing doesn't kill all harmful germs, so the safest route is to thoroughly cook your seafood. As part of this study, researchers conducted a survey of 125 YouTube videos with a total of 5 million views and found that 65% of these videos did not mention proper cooking or freezing of caught fish. The lack of proper food preparation not only promotes the transmission of parasites but can also increase the odds of infection, Hechinger said.
San Francisco Chronicle
30-05-2025
- Science
- San Francisco Chronicle
California's native oysters are unusually well adapted for climate change
Sorry, your browser doesn't support embedded videos. The tiny native oysters of San Francisco Bay managed to outlive the Gold Rush, bay-shore development and decades of punishing pollution. New research shows they have a fighting chance to survive global warming as well. A different species than the farmed Pacific oysters slurped up in restaurants, Olympia oysters are the West Coast's only native oyster species, once forming huge reefs along thousands of miles of coastline from Baja California to British Columbia. Though delicious, they're not as commercially viable and can't be safely harvested from San Francisco Bay because of pollution. But efforts are underway to restore the native oyster in the bay and along the West Coast for its important role in the ecosystem, including providing habitat for baby salmon and crab. 'If we had been here 300 years ago, it would have been this striking, essential part of San Francisco Bay,' said Kerstin Wasson, research coordinator at Elkhorn Slough National Estuarine Research Reserve on Monterey Bay. 'Now it's so rare that most Californians have never seen a native oyster, have never touched one, have never eaten one.' Now, Wasson is the lead author on a study of the native oysters from Mexico to Canada that shows them to be surprisingly well adapted to warmer air temperatures caused by climate change. In recent years, extreme heat waves killed thousands of shellfish that inhabit the same type of intertidal zone, including mussels that were baked in their shells in both the Pacific Northwest and Northern California during low tide. Scientists involved with oyster restoration were really concerned when that happened, said Chela Zabin, ecologist at the Smithsonian Environmental Research Center and one of two dozen co-authors on the study. 'Into the future, are these big heat wave events going through going to affect our ability to restore oysters?' she said. The study, which was published last month and involved significant team effort in 26 locations up and down the West Coast, with funding from the nonprofit organization the Nature Conservancy, showed that native oysters thrive in a wide range of habitats. The researchers assumed that oyster populations, which occupy only a narrow band of the intertidal zone, would cluster closer to the low tide waterline to seek relief from hot air in warmer climates such as Baja California and Southern California. Instead they found that the oysters actually inhabited a larger range, demonstrating that they're more adaptable than expected. That bodes well for oysters farther north, including in the Bay Area, when climate change continues to increase air temperatures there, the authors said. 'What is happening in Baja today is what will happen in San Francisco Bay tomorrow,' Wasson said. On a tour of oyster restoration sites at Point San Pablo in Richmond on Wednesday morning, State Coastal Conservancy Project Manager Marilyn Latta demonstrated how finding native oysters during an extremely low tide was as easy as overturning rocks near the shore — like looking for pill bugs in the garden. The Coastal Conservancy, a state agency, provided funding for native oyster restoration projects at several locations along the Point San Pablo bay shore. That includes at a site called Terminal Four where contractors recently removed a derelict wharf and added new native plants as well as concrete structures, including ones that resemble sand castles, specifically designed to provide habitat for oysters. Zabin held a rock with a dime-size native oyster attached, most likely a baby; adults in San Francisco Bay are only slightly larger than an inch in diameter, making them much smaller than Pacific oysters. In addition to restoration efforts underway in the bay, aquaculture may also be necessary in the future as a backup plan to protect the species, she said. Oysters are known as filter feeders for their ability to clean the water and provide habitat that supports salmon migration back and forth to the sea, Wasson noted. When there are enough of them, they create reefs that provide shoreline protection from waves, she said. However, in California, not enough oysters have been brought back to serve this role. Up and down the West Coast, the native oysters were enjoyed by Indigenous people as well as European settlers, including during the Gold Rush, when they were overharvested and later subjected to pollution and habitat loss, especially as the bay was filled for development. Some oyster farmers, including Hog Island Oyster Co. in Tomales Bay, are experimenting with growing native Olympia oysters — though they're more difficult to produce commercially because they're small and slow-growing, Wasson said. However, growing native oysters may have other advantages, because they are known to be less vulnerable than Pacific oysters to ocean acidification that comes with climate change and inhibits the formation of shells. 'Our poor oysters have suffered a whole bunch of things in the past century,' Wasson said. 'But at least this particular way humans are messing with them is probably going to be OK, at least for the near future.'
Yahoo
28-04-2025
- Science
- Yahoo
Turning a marsh into a climate change laboratory with heat lamps and CO2 pumps
Infrared heaters trained on the Smithsonian Environmental Research Center's wetland in Edgewater help to warm it by 5.1 degrees Celsius, mimicking the potential effects of climate change. (Photo by Christine Condon/ Maryland Matters) This Chesapeake Bay wetland could be an environmental crystal ball. With infrared lamps pointed down at marsh grasses — and heating cables placed beneath them — the environment is 5.1 degrees Celsius hotter than the surrounding area, simulating a future world warmed by climate change. In nearby sections of marsh, carbon dioxide is pumped into structures that look like mini, open-air greenhouses. 'You're never going to get a warmer world without also having higher CO2 in the atmosphere,' said Genevieve Noyce, a senior scientist at the Smithsonian Environmental Research Center, which runs the wetland site. The wetland is just a few miles from the Research Center's headquarters in Edgewater, nestled in a crook of the Rhode River. And it has become a hotbed — pun intended — for several experiments that mimic global warming. The latest research to emerge from the Global Change Research Wetland, or GCREW, was published last week in Science Advances, a peer-reviewed journal. That study captured data for five years, focused not on the wetland's growth, but on its emissions. But one of the experiments here has been ongoing since 1987, leading the center to pronounce that it's likely the world's longest-running field experiment simulating carbon dioxide elevation. The researchers found that adding carbon dioxide stimulated the wetland's growth by about 30% — and allowed its long grasses to start growing earlier in the springtime and stay green farther into the fall. Some years, the grasses can make it until December before they turn entirely brown, said Andrew Peresta, the site's operations manager. But nearly 40 years after the experiment's beginning, Mother Nature is playing scientist, and adding new conditions to the simulation, Peresta said. Rising water levels, a handful of millimeters each year, have begun to change the story, slowing the rate of increased grass growth. 'All of these plants are adapted to grow with their roots in wet soil. But if it's too wet — if the sea level comes up too fast — and they can't keep up, then they start struggling,' Noyce said. The study's long time horizon has allowed scientists to document the marsh's changes over time, including incursions by invasive phragmites, Peresta said. 'A lot of projects are only two to three years long,' Peresta said. 'You might not learn as much as you do with this.' Collectively, coastal wetland environments are among the world's greatest carbon sinks. According to a National Oceanic and Atmospheric Administration webpage, they annually trap carbon at a rate 10 times greater than mature tropical forests, preventing the harmful gases from reaching the atmosphere, where they contribute to warming. But wetlands also release methane, a greenhouse gas that is about 28 times more potent than carbon dioxide when it comes to trapping heat in the atmosphere, according to the Environmental Protection Agency. Traditionally, wetlands have been considered minor producers of the gas. But the Smithsonian researchers have discovered that raising the temperature of the wetland, with the submerged heaters and overhead lamps, speeds up methane production by about four times, compared to the undisturbed wetlands close by, Noyce said. The same was true when researchers added carbon dioxide to the equation, except the increase was less dramatic — about 1.5 times. In other words, if climate change gets worse, it could tip off a domino effect in the wetlands, yielding more emissions that further worsen global warming. 'We knew there was something with adding elevated CO2 to reduce the amount of methane coming out of the plots. But we didn't really know why,' Noyce said. So the researchers looked to the microbial community in the soil beneath the wetland. There, some microbes produce methane, but others consume it. Climate change seems to change the fine balance between these two types of microbes, increasing the methane that is released, said Jaehyun Lee, who was the study's lead author as a post-doctoral researcher at the Smithsonian Center. When carbon dioxide was added to the plots, it stimulated root growth, increasing the amount of oxygen in the soil. This gave more fuel to the microbes that consume methane by oxidizing it, Lee said. Their activity canceled out some of the effect from hotter temperatures, which spurred the methane-producing microbes, causing methane emissions to spike. Even with the increased methane emissions, it seems likely that wetlands will still store more globe-warming emissions than they release, Lee said. But the research proves that the balance is delicate, and could potentially flip in the other direction, said Lee, who is now a senior researcher at the Korea Institute of Science and Technology in South Korea. Since 2016, experiments in Noyce's section of the wetland, known as SMARTX, or the Salt Marsh Accretion Response to Temperature Experiment, have been funded by the U.S. Department of Energy. It remains unclear whether the funding will be impacted by recent Trump administration cuts to scientific research, particularly that which focuses on climate change. The wetland receives three years of funding at a time, and is currently in its last year of the cycle, Noyce said. The team just applied for another three years, she said. The 1987 project is funded by a National Science Foundation grant for long-term research in environmental biology, she said. The new data could help improve the accuracy of climate change modeling, as researchers attempt to predict the amount of globe-warming gases that will be emitted, Lee said. 'When we set the the goal for carbon reduction in the future, to slow down the temperature rise, we also have to consider these types of changes in methane emissions,' Lee said. Otherwise, governments could struggle to reach their carbon reduction goals, he said. The findings, released Wednesday, could also inform wetland plantings and restoration efforts, Noyce said. 'If you can start understanding which plant communities are going to respond in different ways under global change, then you can say: 'Oh, maybe this plant community is going to be better. It might reduce the amount of methane coming out of this sort of ecosystem,'' Noyce said. SUPPORT: YOU MAKE OUR WORK POSSIBLE
