Diphyllobothriasis is found principally among fish-eating people in
the Scandinavian countries, Brazil , Russia, and inparts of Asia
including Japan, Malaysia, Korea and Saudi Arabia.
In the United States
it is found in northern Michigan, Wisconsin, and Minnesota.
Image (LifeCycle)
The
infection is extremely rare in tropical areas.
The causative agent, Diphyllobothrium latum
(fish tapeworm), measures between 3 and 10 meter
(10 and 33 feet) in length and is composed of 3000 or more proglottids.
Humans and other mammals, especially dogs, acquire the infection by
eating uncooked fish or fish products. The worms live in the small
intestine. The presence of multiple worms is not uncommon.
Infected
persons may be symptomless or may suffer from
gastrointestinal disorders, especially abdominal pain.
Occasionally a megaloblastic anemia (bothriocephalus anemia) is seen, especially when
the worm is implanted high in the small intestine. The exact mechanism
for the production of anemia has not been fully elucidated. One
explanation for anemia is that the worm produces an enzyme that
interferes with the association between vitamin B12 and the intrinsic
factor. The uncomplexed vitamin B12 is not absorbed in the ileum and
is available for the worm’s utilization. Megaloblastic hyperactivity
of the bone marrow and even central nervous system degeneration may be
noted in some patients.
Differential
diagnosis should be made primarily between tapeworm anemia and genuine
pernicious anemia. [ Free hydrochloric acid in the gastric juice,
remission after the worm cure without additional therapy, and a
Schilling test value that becomes normal after the expulsion of the
parasite constitute evidence of tape-worm anemia.]
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