from the NY Times:
“Most recently, such concern has been expressed over the dangers of eating raw saltwater fish in the forms of Japanese sushi and sashimi, Scandinavian gravlax, South American ceviche and raw or green herring, which is popular in the Netherlands.
When raw, most saltwater fish that are eaten can be carriers of anisakis simplex, a parasitic roundworm that may invade the gastrointestinal tract of humans, causing mild to serious complications.”