A study conducted by scientists at the Federal University of Santa Catarina in southern Brazil found that a significant number of locally caught tuna are infected with parasites. The research analyzed 53 fish and reported that 96 percent were contaminated by worms, with over 1,600 worms counted in total. The kidneys and hearts of the fish were the only organs consistently free of parasites, while the intestines and muscle tissue showed the highest levels of infection.
The study, published in Ocean and Coastal Research, emphasizes the importance of sanitary inspection and immediate evisceration of fish to prevent the migration of larvae to the muscle tissue. The tuna species examined, known as skipjack or Katsuwonus pelamis, is commercially valuable and was the third most-captured marine species globally in 2022, with 3.1 million tons caught.
While tuna sold for consumption is typically inspected for parasites, some may still go unnoticed. Parasitologists in the U.S. are currently studying worms in expired canned fish to monitor parasite prevalence. The study notes that human infection with Trypanorhyncha larvae is rare, and not all Anisakis species are known to cause disease. Most parasitic worms are rendered harmless during the canning process, but some can cause gastrointestinal symptoms if consumed in raw or undercooked fish.
The presence of parasites can impact the marketability of seafood products, affecting consumer confidence and leading to economic losses for the fishing industry. However, some researchers, like Chelsea Wood from the University of Washington, view the presence of parasites as an indicator of a healthy ecosystem.
The study highlights a need for further research on fish parasites, particularly in key fishing regions worldwide, to understand their dynamics in a changing environment. Wood suggests that while worms are present in many foods, cooking effectively eliminates them, and consuming raw or undercooked food poses the greatest risk of encountering live parasites.
The study is published in Ocean and Coastal Research.