Intestinal anisakiasis. Report of a case and recovery of larvae from market fish

Intestinal anisakiasis refers to the accidental infection of humans by a marine nematode as a result of eating raw fish which contains larval stages of the nematode sub-family Anisakinae. The symptoms mimic appendicitis or regional enteritis and most cases are diagnosed post-operatively. This patient developed acute intestinal symptoms two weeks after eating raw salmon. A degenerating 150 micron larva accompanied by acute inflammation and granulation tissue was found in an adhesive band which extended from her jejunum to her omentum. Examination of a single salmon obtained from the same market where the patient shopped resulted in the recovery of 5 viable larvae, and confirmed the impression that anisakine infection of market fish is common. A related species (Phocanema) causes infestation, but not symptomatic disease. Although common in countries where raw fish is routinely eaten (e.g. Japan), its frequency is not proportional to the size of the group at risk, suggesting that predisposing factors influence the course of exposure. Preventative measures include freezing at -17°C for 24 hours.