This document summarizes the morphology, life cycle, pathogenesis, treatment, and control of Diphyllobothrium latum, the fish tapeworm. It notes that D. latum has a scolex lacking hooks and suckers, with proglottids possessing a central rosette-shaped uterus. It can reach lengths of 2-12 meters with thousands of proglottids. Its life cycle involves eggs passing from the definitive host (dogs, cats, humans) and infecting copepods and fish as intermediate hosts. Humans can become infected by eating contaminated fish and may experience anemia. Treatment involves the drug praziquantel, while control focuses on proper fish handling and prevention of sewage contamination

1. Morphology of Diphyllobothrium
latum
This tapeworm is called "pseudotapeworm or fish
tapeworm or broad tape worm." The scolex of
Diphyllobothrium latum lacks hooks and suckers, but
instead possesses two shallow, longitudinal grooves called
bothria. The scolex is 2.5 mm long and 1.0 mm wide.
Each proglottid of these tapeworms possess a centrally
located, rosette-shaped uterus and associated uterine
pore through which its eggs are released.
This tapeworm may have as many as 3000 or more
proglottids and may range in length from 2 to 12 meters.

2. • Each segment contains single set of
reproductive organs.
• Genital pore and uterine pore open separetely
on the ventral aspect where as in
mesocestoids there is no separate uterine
pore.
• Ovary is bilobed.
• In the gravid segment uterus is spiral tube in
shape.
• Vitelline gland and testes are distributed in
the lateral margin of segment.

3. • The egg is oval, tend to be rounded at one end
and opposite to it operculum is present.
• The eggs are light brown and have dimensions
that average 67-71 µm by 40-51 µm.
• The eggs are unembryonated when passed in
the feces.

4. Life cycle
Definitive host- Dog, cat, fox, man etc
Intermediate host:
1st- cyclops
2nd- fish
Developmental stage:
Egg
Ciliated coracidium
Procercoid(cyclops)
Plerocercoid(fish)
Adult

6. • Man serves as the principal definitive hosts for
Diphyllobothriumlatum, although many other mammals
that eat fresh-water fish (e.g., cat, dog, bear, and pig) may
harbor the adult cestodes.
• Unembryonated eggs pass through the uterine pore of
each of the adult cestode's gravid proglottids.
• The eggs are discharged to the external environment with
the feaces.
• In fresh water, the first developmental stage, the ciliated
coracidium, emerges from the egg and is eaten by the first
intermediate host, an aquatic copepod (a crustacean).

7. • The second developmental stage, the worm-like procercoid
stage, develops within the copepod.
• When the procercoid is ingested by the second
intermediate host, e.g. a fresh-water fish, it develops into a
plerocercoid within the musculature of the fish.
• And finally, mammals like cat, dog, bear etc includding
humans become infected with Diphyllobothriumlatum by
eating the fish and the plerocercoid develops to a mature
tapeworm in the small intestine.

8. Pathogenesis & Symptoms
• In humans this parasite demonstrates vague abdominal
discomfort, diarrhea, nausea and weakness and also
this parasite may produce a serious megaloblastic
anemia.
• The cestode does absorb large amounts of vitamin B12
and that affected humans also have an impaired ability
to absorb this vitamin.
• Pernicious anemia has not been reported in cats or any
other domesticated or wild animals; however, the
experimental infection of dogs with this parasite has
induced decreased red cell numbers and decreases in
total hemoglobin .

9. Treatment
• Praziquantel must be administered at an
elevated dose to be effective against
Diphyllobothriumlatum. A single dose of 35
mg/kg body weight eliminated all
Diphyllobothrium latum from infected dogs.

10. Control
• Prophylaxis involves the freezing or cooking of
fish. At no time should cats be fed raw fish. Such
habits may lead to infections with the infective
plerocercoid stages of D. latum
• If possible, cats should not be allowed to roam
freely or to scavenge dead fish.
• Precautions should be taken against raw human
sewage reaching fresh water lakes in endemic
areas; this has been a major cause of the
infection of the stock of dish in lakes and rivers