Latest news with #freshwaterfish
Daily Mail
6 days ago
- Health
- Daily Mail
Urgent warning over parasite-riddled fish eaten by millions that cause heart attacks
Nearly every single freshwater fish in Southern California may be riddled with parasites that could cause serious health issues in humans. Researchers from the University of California-San Diego revealed that a staggering 93 percent of the 84 freshwater game fish they examined carried two species of trematodes - parasitic worms that infect people who eat raw or undercooked fish. These freshwater species included bluegills, largemouth bass, green sunfish, bluegill-green sunfish hybrids, redear sunfish, black crappies, and the common carp. The two species of flatworms discovered (Haplorchis pumilio and Centrocestus formosanus) typically cause stomach problems, weight loss, and fatigue in people. However, the research team warned that particularly severe infections can lead to heart attacks of strokes. The researchers added that Americans don't often think about freshwater fish having parasites, but the outbreak has already been found in Texas, Florida, and Utah as well. Ryan Hechinger, an ecologist at UC San Diego's Scripps Institution of Oceanography said: 'These parasites are here in the US, and they're infecting fish that people are eating.' The fish are typically found in warm, shallow waters with vegetation nearby. However, this has also become a thriving habitat for the invasive snail Melanoides tuberculata, which carries the trematodes spreading to local fish. Freshwater game fish include multiple species that live in lakes, rivers, or reservoirs. They're popular targets for recreational fishing, often because anglers consider them fun to catch or good to eat. Fully cooking any fish caught in these locations will eliminate the parasites, according to guidelines from the US Food and Drug Administration (FDA). For those who eat raw fish, in items like sushi, they need to freeze their catch for at least a week to kill the trematodes. The parasites were mostly in the fins and gills, though H. pumilio was often found in the muscle tissue near fin bases, which could end up in fish fillets. Overall, researchers found 78 of the 84 fish they examined are carrying the parasitic worms. Other popular freshwater game fish that could be at risk from the snail's parasites include catfish, trout, salmon, and perch. The study authors fear that millions of people could be at risk of contamination, based on the amount of interest in eating raw fish on social media and platforms like YouTube. During their study, published in the Journal of Infectious Diseases, Hechinger's team also looked at 125 popular YouTube videos which featured people eating raw freshwater fish. Nearly two-thirds (65%) did not mention the proper cooking or freezing methods for these fish, which the team believes is promoting bad habits and will likely lead to the spread of dangerous parasites among seafood lovers. According to the study authors, many videos also spread false information, like claiming that marinating fish in citrus juice or choosing 'healthy-looking' fish eliminates the risk of parasites, which isn't true. While there hasn't been widespread outbreak of trematode infections reported in California or elsewhere, Hechinger said that doesn't mean many people aren't getting sick. 'Nobody is looking for cases and doctors aren't required to report them,' he explained. Hechinger added that his team believes fish-borne trematode infections should be added to the list of diseases doctors have to report to public health officials. The FDA explains that improper cooking of fish means it hasn't reached an internal temperature of at least 145°F. For those freezing their fish to eat it raw, it needs to reach a temperature of -4°F for seven days or be flash-frozen at -31°F for at least 15 hours. When fish is improperly cooked or frozen, the trematodes can survive and then infect the human body when eaten. Once swallowed, these parasites enter your stomach and not even the stomach's acids can kill the larvae, which are protected by a cyst-like covering. In the small intestine, digestive enzymes break down this covering and release the young worms into the gastrointestinal tract. Over the next few days to weeks, the juvenile worms grow into adults, which are about one to two millimeters long. As the worms multiply and attach themselves to the small intestine, they irritate the intestinal lining, leading to symptoms like stomach pain, diarrhea, nausea, and indigestion. After eating infected fish, most symptoms of H. pumilio or C. formosanus typically start within one to two weeks. If left untreated, the more severe symptoms of a chronic infection could start to show one to three months after eating the fish. Once doctors diagnose someone with an infection, the standard treatment is an anti-parasitic medication called Praziquantel. The infections typically clear up within days after taking the drug.
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The Independent
7 days ago
- General
- The Independent
California fish carry human-infecting parasites that can cause stroke or heart attack, researchers find
More than 90 percent of popular freshwater game fish in Southern California contain a parasite that is capable of inducing strokes or heart attacks in the humans who eat them. Researchers said the parasites were two species of flatworms known as trematodes. At no more than a few centimeters in length, the flukes – a class of flatworms – can result in weight loss or lethargy. Although rare, infection has also resulted in more severe consequences. 'Americans don't usually think about parasites when they eat freshwater fish because it hasn't historically been an issue here,' Ryan Hechinger, an ecologist and parasitologist at UC San Diego's Scripps Institution of Oceanography, said in a statement. 'But these trematodes have now been widely introduced in the U.S. and that means that doctors and the public should be aware.' He is the senior author of the study which was published Tuesday in the Journal of Infectious Diseases. It was funded by the National Institutes of Health. To identify this issue, Hechinger, the University of Nebraska's Daniel Metz, and former Scripps graduate student and Smithsonian Environmental Research Center marine scientist Emma Palmer examined 84 fish from seven different species in 2023. Those fish included largemouth bass and bluegill, which were collected from five frequented fishing locations in San Diego County. Of those, 93 percent were infected with the Haplorchis pumilio parasite, and some were the host to thousands. Two of the five locations yielded positive results for the second parasite known as Centrocestus formosanus, which occurred in 91 percent of the fish. Historically, the trematodes have infected people in Southeast Asia and likely arrived in the U.S. more than a decade ago inside an invasive aquatic snail known as the red-rimmed melania. That snail is found in 17 states and Puerto Rico. Previous work led by Hechinger had found that the red-rimmed melania and its parasites are widespread in the Golden State. So, what is the risk to Californians and Americans at large? Hechinger says there haven't been any reported cases of parasites infecting Americans yets, but 'nobody is looking for cases and doctors aren't required to report them.' Californians should make sure to monitor fish advisories for any changes. The risks posed by them are easy to avoid as, if you fully cook your fish or freeze any that's intended to be eaten raw for at least a week, the parasites will die. Although, the authors found that many Americans are likely consuming freshwater fish without taking the proper precautions. The greatest health threats come from repeated infection over many months or years. Foodborne trematode infections cause two million life years lost to disability and death worldwide every year, according to the World Health Organization. They recommend that fish-borne trematode infection be added to the list of diseases doctors are required to report to public health officials. 'These parasites are here in the U.S., and they're infecting fish that people are eating,' said Hechinger. 'We hope this study can help make public health officials, doctors and the public more aware.'
