LUMINAL FORM

The larvae that cause luminal anisakiasis are incapable of penetrating the mucosal surface of the digestive tract, and are accompanied by a tingling, tickling throat until the patient actually coughs up or can otherwise extract a nematode. Symptoms occur one hour to two weeks after consumption, and usually only one nematode is recovered. Most cases in the U.S. are of this form.

GASTRIC FORM

This form is usually caused by the Anisakis species, and symptoms mimic gastritis or an ulcer, accompanied by nausea, vomiting, and abdominal pain. Symptoms first occur 12 hours after consumption of the larvae.

INTESTINAL FORM

All intestinal cases are caused by the Anisakis species, and are characterized by the burrowing of the larval nematodes into the wall of the intestines, possibly even burrowing through to the cavity, causing intraperitoneal anisakiasis (see below). Any portion of the intestines may be invaded, but the terminal ileum is the most common site. The larvae produce a substance that recruits eosinophils to the site, causing the formation of a granuloma around the worm in the tissue.

INTRAPERITONEAL FORM

In severe cases, the larvae may completely penetrate the intestinal wall and migrate to the liver, gallbladder, lymph nodes, and mesenteries of the host. Often, symptoms mimic gastric cancer, appendicitis, pancreatic cancer, or peritonitis. The prognosis of this form of anisakiasis is the worst.

Section of an anisakid worm within an abcess in the stomach of a Japanese patient. The parasite was found within a typical lesion associated with anisakiasis.