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PHYLUM PLATYHELMINTHES
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Collectively called the FLATWORMS
A
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C
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A
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erinacei ;
S
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ranarum
B
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Diphyllobothrium latum (Broad Fish Tapeworm)
Common Name:
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Fish Tapeworm

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Adult worm is yellowish grey in
color
Dark central markings in the strobili
are due to the egg-filled uterus
Measures 3 to 10 meters in length
Life-span is for a period of 5 to 15
years
Scolex :
 Is spoon-shaped or spatulate
 bears 2 slit-like grooves
(BOTHRIA)

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Broad Fish Tapeworm

Morphology:

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 has no rostellum and no
hooklets
Neck is thin and unsegmented and
is much longer than the head
3,000 to 4,000 proglottids
A mature segment is filled with
male and female reproductive
organs
Terminal segments shrink and
becomes empty as eggs are
constantly discharged

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Dried up segments break offfrom
the body in chains and are passed
out in the host’s feces
Uterus at the center of the
segment appears in the form of a
rosette

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OVA
66 X 44 µm w/ 58-76 µm length and
40-51 µm width
Oval
Bile stained
Contains abundant granules and
unsegmented ovum
Inconspicuous operculum at one
end and a small knob at the other
end (abopercular knob)
Does not float in saturated solutions
of common salt
A single egg gives rise to a single
larva
Not infective to man
About 1 million released everyday

LIFE CYCLE
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1st IH (Infective stage:
Coracidium)
- Copepods (Cyclops or
Diaptomus)
nd
2 IH (Infective stage:
Procercoid)
- Fresh water fish, pike, trout,
salmon, perch
Definitive Host (Infective Stage:
Plerocercoid)
- Man, Dog, Cat
- Small intestine
Mode of infection
- Ingestion of imperfectly
cooked infected fish or roe
containing plerocoid
larvae

* Proglottids disintegrate only when the
segment completes its reproductive
function

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LARVAE
Passed first in water and then in
the respective intermediate hosts
3 stages:
 First Stage Larva
- Coracidium
- Ciliated oncosphere that
develops from egg in water
 Second Stage Larva
- Procercoid
- Spindle-like solid body w/
cephalic invagination
- Found inside the Cyclops
(1st IH)
 Third Stage Larva
- Plerocercoid
- Head is invaginated in the
neck
- Found in the fresh water
fish (2nd IH)

Infection:
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Diphyllobothriasis
Broad fish tapeworm
infection

Signs and Symptoms:
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G
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disturbances
Hyperchromic and
megaloblastic anemia
with thrombocytopenia and
leukopenia
Mistaken for Pernicious
anemia (Vit

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