Study finds high prevalence of worms in sushi-grade tuna

A study conducted by Brazilian scientists revealed that 96% of locally-caught skipjack tuna tested were contaminated with worms. The research, published in the journal Ocean and Coastal Research, involved the analysis of 53 tuna specimens using advanced microscopy. The total number of worms found amounted to 1,600, primarily located in the intestines, followed by muscle tissue and stomach, while kidneys and hearts showed no contamination. The findings raise concerns about the sanitary inspection of seafood, especially given the global popularity of skipjack tuna, which saw 3.1 million tons caught in 2022. The researchers emphasized the need for immediate removal of fish viscera to prevent parasites from migrating to the edible portions. Previous research from the University of Washington indicated a significant increase in herring worms in raw fish over several decades, with the prevalence rising from one worm per 100 fish to one worm in every fish caught. Consumption of raw or undercooked fish infested with these parasites can lead to gastrointestinal issues, although symptoms typically resolve within a few days. Experts suggest that thorough cooking of fish can mitigate these risks. Some researchers, however, view the presence of parasites as an indicator of fish freshness, with Chelsea Wood, a parasitologist at the University of Washington, stating that worms can signify a healthy ecosystem.