Adult Anisakis is
a
parasite (usually, but not only,
founded in the stomach) of marine mammals such as whales or dolphins,
which
are the definitive host. Eggs produced by female worms pass with the
faeces
of the host into the ocean water; then the larvae enter small marine
invertebrates
such as crustaceans of the family Euphasidae and develop into several
phases until reach the stage III. When a fish eats the crustacean, the
larvae stage
III is released and pass thought the gastrointestinal tract, then can
migrate
to fish muscle. If a marine mammal eats the infected fish, the larvae
is
released and established in the stomach.
When humans eat the infected fish, raw or
inadequately
cooked, the nematode (larval stage III) may enter the tissue of the
gastrointestinal
tract and then it can cause different problems associated with gastric
and
abdominal infections; occasionally the worm can migrate to another
viscera.
Generally, the
clinical symptoms of acute
intestinal
anisakiasis include violent epigastric pain, nausea, vomiting,
diarrhoea,
and sudden abdominal pain similar to an acute abdominal syndrome such
as
intestinal obstruction, appendicitis or peritonitis. Additional
disorders
have been reported such as urticaria, pulmonary disturbances, allergic
oedema
or polyarthritis.Chronic anisakiasis produces mild symptoms such as
abdominal
pain, nausea, vomiting, and some times bloody stools, that could
suggest
a stomach tumour.
Parasitological diagnosis is made finding the worms by
endoscopy technique or by biopsy of the tissue. Serological tests are
very
important in chronic anisakiasis where diagnosis by endoscopy is not
possible.
The treatment for most infections is the removal of the
parasites surgically or by the use of though endoscopy forceps. No
drugs
have been approved for treatment of human anisakiasis.
Anisakis simplex is the nematode species most frequently
associated with human disease in Europe. The human disease acquired by
an
intake of parasited marine fish species is named anisakiasis.
Anisakiasis was first recognised in Holland in the 1960
(mainly because the ingestion of matjest-herring), but it is in Japan
where
it constitute a major public health risk because the habit of eat raw
fish
(more than 2.000 occurrences per year are usually recorded). The
disease
was initially associated with the use of refrigerated fish stored for
long
periods. Furthermore, cold smoking, marinating, salting or brining are
unable
to kill the worm. Only an appropriate freezing (at -20ºC for 72
hours)
or heating above 55ºC for 10 seconds can ensure the absence of
nematodes
alive.
The anisakiasis cases recorded more recently in Europe
are associated with the ingestion of brined, marinated or cold-smoked
fish
species, and it must be pointed out than the recently habit of eat raw
fish
in Japanese type restaurants can be considered a serious risk because
the
high parasitation rates detected in fresh fish caught in European
waters.
Some authors (Bier, J.W. et al. 1987. Balliere´s
Clinical Tropical Medicine and Communicable Diseases 2:723-733) have
suggested
that the infection of fillets may be related to body cavity burdens,
subsamples
that can not be immediately frozen or gutted could be checked for
numbers
of parasites. If the number exceeds 15, the fish should be banned for
human
consumption according with these researchers.
Nowadays this recommendation becomes more important because
the recent foundlings on the allergic reactions of some consumers (and
even
dermatological reactions of fish handlers) to the parasite (Iglesias,
R.
1998. La anisaquiosis y su diagnóstico. Doctoral Thesis.
Universidad
de Santiago de Compostela).
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