I found this in another group, and not the sushi one, which I don't follow.
So I don't know what sort of follow-up this has had. It would have been
nice if it said what types of fish had this problem. Don.

Newsgroup: alt.food.sushi
Subject: Latest Amer. Gast. Insten. Journal - sushi risk
From: [log in to unmask] (ada)
Date: Wed, Jul 29, 1998 23:20 EDT

Risk of parasitic infection from sushi
A recent report warns of the risk of the gastrointestinal illness
  anisakidosis from tiny parasites in sushi (raw fish).
    - researchers at Japan's Yokohama City University School of
      Medicine say the number of cases of anisakidosis reported have
      been increasing and are expected to keep increasing.
    - anisakidosis is caused by the ingestion of the larval form
      of the anisaki worm; the worm is found naturally in the
      intestinal systems of various marine mammals and fish.
    - authors say infestation with the parasite can result in
      the immune system trying to surround the organisms with
      a mass of white blood cells, which can result in the
      formation of masses called granulomas that can become
      large enough to block intestinal tracts.
    - the report is in the American Journal of Gastroenterology
      (1998;93:1172-1173).