Parasitic flatworms have been found in popular US freshwater game fish, posing health risks to those who eat them raw.
United States: It is found that in the US, many freshwater game fish like bluegill, largemouth bass, and black crappie have parasitic flatworms that can harm people, as revealed in a new study.
More about the news
About 90% of the popular game fish studied in Southern California contained flatworms named trematodes, the researchers found and reported recently in The Journal of Infectious Diseases.
According to senior researcher Ryan Hechinger, an ecologist and parasitologist at the University of California-San Diego Scripps Institution of Oceanography, “Americans don’t usually think about parasites when they eat freshwater fish because it hasn’t historically been an issue here,” US News reported.
“But these trematodes have now been widely introduced in the U.S., and that means that doctors and the public should be aware,” he noted.
#Over 90% of freshwater game fish in #SouthernCalifornia harbor invasive trematode #Parasites capable of infecting humans, highlighting an emerging public health risk. Proper cooking or freezing is advised. @ucsandiego https://t.co/ngio2uo43B
— Phys.org (@physorg_com) June 4, 2025
It’s not a problem, Hechinger noted, since fully cooking fish will get rid of the flatworms. Any fish bought for sushi should be frozen for at least a week if you want to eat it raw.
Shockingly, dozens of YouTube clips were found showing people being at risk for infection after eating untreated fish straight from live animals.
“Nearly 5 million views shows there is widespread interest and possibly a widespread practice of folks eating freshwater fish raw,” lead researcher Emma Palmer stated.
She currently works as a marine scientist at the Smithsonian Environmental Research Center, which is located in Edgewater, Md.
Most of the time, these infections lead to issues like stomach illnesses, loss of weight, and a lack of energy in people, studies say, US News reported.
It is reported by the World Health Organization (WHO) that these flatworms can settle in the lungs or the ducts of the liver and gallbladder.
Plenty of severe liver and lung damage may occur if a person does not receive proper treatment for the infection.