The Unappetizing Truth About Sushi: Scientists Find Parasites in 96% of Tuna

If you were planning to order a sushi platter tonight, you may want to reconsider. A new study has found that tuna can be teeming with parasitic worms.

Researchers from the Federal University of Santa Catarina in Brazil examined 53 specimens of local fish and uncovered a disturbing statistic: 96% of the samples were infected with parasites. In total, the scientists recovered more than 1,600 worms.

Even more concerning is that one of the species identified — Anisakis — poses a direct threat to human health.

“The worm can penetrate the walls of the human intestine, causing an acute, temporary infection accompanied by abdominal pain, nausea, vomiting and diarrhea,” the researchers warn.

The scientists focused their research on skipjack tuna (Katsuwonus pelamis), a species widely consumed around the world.

“Skipjack tuna has high economic value and is widely used by the fish-processing industry, primarily for the production of canned fish,” the authors of the study, published in the journal Ocean and Coastal Research, noted.

Using scanning electron microscopy, the researchers identified two main groups of parasites — Anisakis and Trypanorhyncha — in 96% of the fish examined.

Most of the worms were found in:

• The intestines — 596 parasites;
• Muscle tissue — 441 parasites;
• The stomach — 408 parasites.

Cooking the Fish Does Not Guarantee 100% Safety

The researchers emphasize that eating raw or undercooked fish containing Anisakis parasites can be extremely dangerous. Moreover, even heat treatment may not always eliminate the risks.

• “Cooking and/or freezing seafood may be insufficient to prevent hypersensitivity reactions [allergic reactions],” the researchers warn.
• The scientists also detected heat-stable allergens in the extracts, raising questions about whether fish that has contained parasites can ever be considered completely safe to eat, even after being thoroughly cooked.