Southern California fishermen, if you’re thinking of making sushi with fresh fish you’ve caught from a nearby lake, better not.
Flatworms and two other dangerous parasites that are ingested by fish have been found in lower-elevation lakes and reservoirs in five counties, according to new findings by Scripps Oceanography researchers.
“We document that three human-infectious trematodes and their first introduced intermediate snail host (Melanoides tuberculata) are widespread in southern California,” the authors write in the Journal of Infectious Diseases.
This includes Sunbeam and Weist Lakes in Imperial County, Rancho Jurupa Park Pond in Riverside County, and Seccombe Park Lake in San Bernardino County.
In all, the invasive flatworms, tremors, and snails they grow on were found in 19 of the 41 bodies of water surveyed, but the researchers cautioned that the surveys were a representative sampling and many more fishing holes in the region and in the United States. they are probably infected.
“We have every expectation and preliminary documentation that trematodes are found in the tissue of several fish in Southern California, including those that are commonly fished,” the authors wrote. “The current and potential risk of human infection in California clarifies the need to consider the introduced snail and its parasites from a public health perspective anywhere in the United States where the snail has been introduced.”
The types of parasites found can cause intestinal disease and eye damage, according to the paper and other published research.
The best way to avoid becoming infected, the authors wrote, is to immediately freeze, for up to a week, or thoroughly cook any fish you’ve caught. And be sure to wash any knives you use well, too.
“The best approach as of now is to follow the FDA guidelines for fish: either cook the fish thoroughly or freeze it in a home freezer (at about 4 F or minus 20 C) for 7 days,” said co-author Daniel Metz in an email. “It’s also important to know that these parasites can be transferred to the utensils used to prepare the fish (such as fillet knives or escalators). So if you use a knife to cut a nice fillet from your freshly caught fish, be sure to wash it before using the same knife to cut vegetables or other foods that won’t be cooked!”