According to the definition of the Center for Disease Control and Prevention (CDC), Anisakiasis is a parasitic disease caused by anisakid nematodes (worms) that can invade the stomach wall or intestine of humans. The transmission of this disease occurs when infective larvae are ingested from fish or squid that humans eat raw or undercooked, like in sushi or sashimi. In some cases, this infection is treated by removal of the larvae via endoscopy or surgery.
The worm has normally a lenght ranging from 0,3 to 1 inch and is therefore visible to the naked eye.
Adult stages of Anisakis simplex usually are embedded in the mucosa of marine mammals, where they reside in a stable manner. Unembryonated eggs produced by adult females are passed in the feces of marine mammals. The eggs become embryonated in water and first-stage larvae are formed in the eggs. The larvae molt, becoming second-stage larvae. After their hatching from the eggs, they become free-swimming and are then ingested by crustaceans, where they develop to third-stage larvae and become infective to fishes and squids. Fishes and squids maintain third-stage larvae that are infective also to humans and marine mammals.
Which are the symptoms?
The most common symptoms of the infection include:
- Abdominal pains
- Faecal blood
In the most serious cases, infection can take chronic forms with ulcers and intense abdominal pains, involving other organs such as liver, spleen, pancreas, blood vessel and myocardium. Allergic reactions with rash, itching and, although infrequently, anaphylaxis, can also occur, owing to the biochemical substances which are secreted by the larvae.
How is it diagnosed?
Generally, a previous history of ingestion of raw or undercooked fish is very helpful. A definitive diagnosis can be made only by endoscopy, radiography, or surgery if the worm has embedded.
How can be prevented?
Never eat raw or undercooked fish or squid.
The FDA recommendations for seafood preparation or storage, in order to kill parasites include:
Cooking (Seafood in General)
- Cook seafood adequately (to an internal temperature of at least 145F°/63°C).
- At -4°F (-20°C) or below for 7 days (total time), or
- At -31°F (-35°C) or below until solid, and storing at -31°F (-35°C) or below for 15 hours, or
- At -31°F (-35°C) or below until solid and storing at -4°F (-20°C) or below for 24 hours.
You can find more information on Safe Food Handling at the Partnership for Food Safety Education