Sushi Parasites On the Rise
The University of Washington has recently published their scientific findings on the presence of worms in raw fish. Raw fish, often consumed in the forms of sushi, sashimi, nigiri, or undercooked fish, are already thought of as a high risk food for food poisoning because of the risk for bacteria, such as Salmonella and E. coli. However, recent studies have found a more dangerous implication for raw fish: parasitic worms. The herring worm, known as Anisakis, has increasingly been found in raw fish and unknowingly consumed by humans and marine mammals. In fact, a meta-analysis conducted by the journal Global Change Biology discovered the herring worms presence in the past 40 years has increased 283-fold.
Ingesting Anisakis worms infects the subject with Anisakiasis, which often presents symptoms of food poisoning, leading to a misdiagnosis. The symptoms of Anisakiasis include diarrhea, vomiting, and nausea. These symptoms are caused by the Anisakis worm invading the intestinal wall of its host. If the host is human, the herring worms cannot reproduce and only live for a few days; however, in marine mammals such as squid or marine fish, the worms can reproduce and survive in its host. The herring worms are then deposited by its marine mammalian host via feces, but it has yet to be determined how long the worms stay in their host. The length of the Anisakis worms infestation in their marine host is hypothesized to be increasingly detrimental because of the loss of nutrients caused by the food poisoning like symptoms of Anisakiasis.
To avoid consuming the parasite, raw fish should be thoroughly checked for any sighting of the worms, cutting large pieces in half. Herring worms typically measure out to 2cm when fully uncoiled, being fully visible to the naked eye. Anisakiasis has no treatment unless the worms are unable to pass in their human host; these cases are often treated endoscopically or by surgically removing the worms.