Diphyllobothrium latum, the fish tapeworm, is acquired by eating infected raw fish and causes diphylothriasis. It has a complex life cycle involving crustaceans and fish as intermediate hosts. Humans and other fish-eating animals are definitive hosts. Symptoms are generally mild but may include diarrhea, abdominal pain, and fatigue. Diagnosis is confirmed by finding the tapeworm's eggs in feces. Preventing raw or undercooked fish consumption and proper sanitation can control transmission.

1. Diphyllobothrium Latum
2019
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2. Introduction
• Diphyllobothrium latum, the fish tapeworm, is
the longest tapeworm in humans, averaging
ten meters long (Also referred to as broad
tapeworm).
• Infection with Diphyllothrium latum causes
diphyllothriasis and is acquired by eating
infected raw fish.
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3. Distribution
• D. Latum is worldly distributed in river and
lake areas of Europe, Uganda, North America
and far East
• It is also found in parts of Asia, south America,
central Africa
• In countries like India, where fish is eaten only
after cooking, the infection does not occur.
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4. Habitat
• The adult worm is found in the small intestine
(ileum) of humans, cats, dogs, foxes where it
lies folded in several loops with the scolex
embedded in the mucosa.
• The first host of the larva is the Crustacean of
genus Cyclops or Diaptomus
• The second host of the larva is a fresh water
fish and there are a number of various species
that can serve as intermediate host
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5. Transmission
• Transmission is by ingesting the infective larva
known as plerocercoid in raw or insufficiently
cooked fresh water fish such as trout, perch or
pike
• Unlike the other tapeworms described, the life
cycle of D. latum requires two intermediate hosts
i.e. Crustacean and fish
• Definitive hosts include humans and fish eating
animals such as dogs, cats, foxes, bear and
leopards
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6. The life cycle of D. latum
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7. Life cycle cont…
After ingestion of plerocercoid larva
Plerocercoid becomes attached to wall of the
small intestine and within 2-4 weeks develops
into a mature tapeworm
Many eggs are produced and discharged
directly by the worm into the lumen of the
intestines and passed in feces
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8. Life cycle cont…
• For the life cycle to be continued, the eggs
must reach fresh water
• Within 1-2 weeks, the eggs mature and hatch
releasing spherical ciliated embryos called
coracidia
• The coracidia are ingested by a crustacean like
crabs, lobsters, crayfish, shrimp, krill, woodlice
and barnacles
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9. Life cycle cont…
• Within few weeks, elongated larvae called
Procercoids develop inside the crustacean
• The infected crustacean is ingested by a fresh
water fish
• In the second intermediate host, the Procercoid
are released and develop into infective
plerocercoid which migrate to the muscles and
connective tissue of the fish
• The life cycle is completed by human or animal
definitive host eating fish containing
plerocercoids
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11. Clinical features and pathology
• D. latum can live for many years in human host
• Approximately four out of five cases are
asymptomatic and may go many years without
being detected
• Symptoms of Diphyllobothiriasis are generally
mild, and can include diarrhea, abdominal pain,
vomiting, weight loss, fatigue, constipation and
discomfort etc. due to toxins released by
tapeworm
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12. Clinical features and pathology cont…
• Occasionally megaloblastic anaemia may
develop due to uptake of vit B12 by the
tapeworm in competition with the host
• It is more likely to occur when the tapeworm
is situated in the upper part of the jejunum
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13. Morphology of adult D. latum
• The adult worm is composed of three fairly
distinct morphological segments: the scolex
(head), the neck, and the lower body.
• Each side of the scolex has a slit-like groove,
which is a bothrium for attachment to the
intestine.
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14. Morphology of adult D. latum cont…
• The scolex attaches to the neck, or
proliferative region.
• From the neck grow many proglottid
segments which contain the reproductive
organs of the worm.
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15. Adult worm
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16. Morphology of adult D. latum cont…
• Adults can shed up to a million eggs a day.
• In adults, proglottids are wider than they are
long (hence the name broad tapeworm).
• As in all pseudophyllid cestodes, the genital
pores open mid-ventrally
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17. Laboratory diagnosis
• Confirmation of D.latum infection is by;
Finding eggs in feces
Occasionally detecting mature segments in
feces
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18. Examination of faeces for D. latum eggs
• Many eggs are usually present in the faeces
because they are constantly discharged
through the uterine pore.
• They can therefore be easily detected by
direct examination of a fecal specimen
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19. Identification features of D. latum
eggs
• It is yellow-brown and oval
in shape, measuring about
70 x 45µm.
• Has an operculum (lid)
which is usually difficult to
see.
• Contains a mass of
granulated yolk cells
surrounding an
undeveloped ovum.
• Sometimes a small
projection is visible at the
non- operculated end of the
egg.
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20. Identification features of a D. latum
segment
• Often not found in the faeces
because they tend to disintegrate
in the intestines.
• When found, they often appear
shrunken and empty.
• Undamaged mature segments of
D. latum are wider than they are
long, measuring 10–20mm across
by 3–7mm long.
• The genital pore is found in the
centre of the segment and not on
the lateral margin as is the case
with Taenia species.
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21. Measures to prevent and control D. latum
infection
• Avoid eating raw or undercooked fish which may
contain plerocercoids.
• Health education about proper preparation of
fish. Fish that is thoroughly cooked, brined, or
frozen at -10 °C for 24–48 hours can be consumed
without risk of D. latum infection.
• Screening and successful treatment of people
infected with the parasite
• Preventing the eggs reaching water by providing
adequate latrines combined with health
education.
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22. Thank you
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