GoKawiilA fatty tuna that is often used for sashimi or canning may be swimming with parasites more often than not.
When scientists at the Federal University of Santa Catarina in southern Brazil analyzed 53 locally caught fish, they found nearly all were contaminated by worms.
According to a brief communication published in Ocean and Coastal Research, the research team counted more than 1,600 little worms in total.
Using powerful microscopy tools as aids, they found that the kidney and heart were the only organs free of parasites in every fish.
Otherwise, the worms and their signs were everywhere.
Of the 53-fish haul, 96 percent were infected by parasites.
The intestines were the most heavily infected organ, followed by the muscle tissue – notably, the bit we eat – and then the stomach.
"These results highlight the importance of sanitary inspection," the study authors conclude, "and emphasize the importance of immediate evisceration to avoid the migration of larvae from the viscera to the musculature."
(A) Necropsied tuna; (B) Internal Organs: (1) spleen, (2) heart, (3) intestine, (4) gallbladder, (5) liver, (6) gonad, (7) eyes; Infected tissues: (C) Rhadinorhynchus sp.; (D) Trypanorhyncha; and (E) Anisakis sp. (Maia de Aquino et a., Ocean Coast. Res., 2026)
The study from Brazil is small and covers only a single point in time, but it suggests that tuna in this region commonly host two worm genera: Trypanorhyncha and Anisakis.
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