simplex and related worms
simplex (herring worm),
Pseudoterranova (Phocanema, Terranova) decipiens (cod
or seal worm), Contracaecum spp., and Hysterothylacium
(Thynnascaris) spp. are anisakid nematodes (roundworms) that
have been implicated in human infections caused by the consumption
of raw or undercooked seafood.
is generally used when referring to the acute disease in humans.
is diagnosed when the affected individual feels a tingling or tickling
sensation in the throat and coughs up or manually extracts a nematode
worm. With severe cases there is acute abdominal pain, much like
acute appendicitis accompanied by nausea. Symptoms occur from an
hour to about 2 weeks after eating raw or undercooked seafood.
one nematode is usually recovered from a patient.
cases where the patient vomits or coughs up the worm, the disease
may be diagnosed by looking at the worm. Other cases may a scope
that allows the physician to examine the inside of the stomach and
the first part of the small intestine and use a mechanical forceps
to remove the worm.
cases are diagnosed upon finding a granulomatous lesion with a worm
are the principal sources of human infections with these larval
worms. The adults of A. simplex are found in the stomachs
of whales and dolphins. Fertilized eggs from the female parasite
pass out of the host with the host's feces. In seawater, the eggs
embryonate, developing into larvae that hatch in seawater. These
larvae are infective to minute crustaceans and other small invertebrates.
The larvae grow in the invertebrate and then become infective for
the next host, a fish or larger invertebrate host such as a squid.
The larvae may penetrate through the digestive tract into the muscle
of the second host. The nematode larvae move from the viscera to
the flesh f fish caught by fishermen so it is important to gut the
fish quickly after catching. These parasites are known to occur
frequently in the flesh of cod, haddock, fluke, pacific salmon,
herring, flounder, and monkfish.
than 10 cases are diagnosed in the U.S. annually. Raw, undercooked
or insufficiently frozen fish and shellfish transmit the disease.
cases of anisakiasis are extremely painful and require surgical
intervention. Physical removal of the nematode(s) from the lesion
is the only known method of reducing the pain and eliminating the
cause (other than waiting for the worms to die). The symptoms may
persist after the worm as irritation may also be caused by nematode
processors use candling or examining fish on a light table. This
method is not totally effective.
the most reported cases because of all the raw fish consumed there.