It has been discovered that over 90% of common game fish in Southern California are infected with invasive, parasitic worms that can spread to humans.
According to a study conducted by researchers from the Scripps Institution of Oceanography at the University of California, San Diego, two types of parasitic flatworms called “trematodes” were found to infect five species of freshwater fish from San Diego County.
Human worm infections usually result in gastrointestinal issues, fatigue, and weight loss, but in extreme situations, heart attacks and strokes have been reported.
“Americans don’t usually think about parasites when they eat freshwater fish because it hasn’t historically been an issue here,” paper author and ecologist Ryan Hechinger stated.
He did, however, add: “These parasites are here in the U.S., and they’re infecting fish that people are eating.”
“We hope this study can help make public health officials, doctors and the public more aware.”
The researchers sampled 84 fish from five well-known fishing locations in San Diego County, representing seven different species, including largemouth bass and bluegill, for their study.
Haplorchis pumilio and Centrocestus formosanus are the two invasive trematode species that the team found in the fish.
Ninety-three percent of the fish sampled had H. pumilio, and some of those fish had thousands of the parasitic worms. In contrast, 91 percent of the fish from two of the sites had C. formosanus.
It is thought that both worms entered the United States from Southeast Asia over ten years ago by entering the body of one of their hosts, the Malaysian trumpet snail (Melanoides tuberculata), an invasive aquatic species.
M. tuberculata and its parasites are common in California, and they are currently found in 17 states and Puerto Rico.
In their life cycle, the worms inhabit three different hosts: a trumpet snail initially, followed by a fish, and ultimately a warm-blooded vertebrate, such as a person or bird, if the infected fish is unfortunate enough to be consumed.
There is “no need to panic,” according to Hechinger, because the parasite risk may be eliminated by boiling the fish or, if you’re going to eat it raw, freezing it for at least a week in advance.
However, the team’s analysis of social media videos in addition to their fieldwork showed that some Americans are eating raw freshwater fish without taking these safety measures, which puts them at risk for infection.
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Emma Palmer, a marine biologist at the Smithsonian Environmental Research Center and the paper’s author, said in a statement, “Nearly 5 million views demonstrate there is widespread interest and possibly a widespread practice of folks eating freshwater fish raw.”
While pursuing her doctorate studies at the Scripps Institution of Oceanography, Palmer carried out the parasite research.
The researchers stated it’s unknown what effect the invasive worms may be having on Southern California’s fish enthusiasts.
The researchers have suggested that these fish-borne worm infections be included in the list of illnesses that physicians must report to public health officials in order to better monitor the parasites.
