Anisakiasis can be classified into four clinical presentations
depending on where the larvae is found:
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.
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.
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.
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.
Anisakidae larvae penetrating the gastric wall.
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.