Class%20Cestoidea

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Class Cestoidea

• The Tapeworms

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What is a Tapeworm?

• Trematodes are in blood or tissues, but need to
  get eggs or cysts in digestive tract to continue
  cycle. Sometimes the eggs dont get there.
• Living in the digestive tract seems like a good
  place for a parasite.
• One problem How could it hold onto the side of
  the digestive tract as food is pushed forcibly
  through it?

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Would this be sufficient?
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Or these?
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But as a Platyhelminth (and by definition without
a circulatory system) these parasites have to be
thin and flat. This makes their bodies fragile
and get easily broken up as food is forced over
them.
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Yes, they would tend to break up. So tapeworms
have taken this limitation and turned it into an
advantageous adaptation. Evolution of
Proglottids. Sections that purposely break off.
When life gives you lemons
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General Body Shape of a Tapeworm

1. Scolex
2. Neck
3. Strobila made up of proglottids

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Scolices
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Scolex (pl Scolices)

• Sucker like Organs of Scolex
• Acetabula Cup shaped, circular with heavy
  muscular wall usually four.

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Scolex (pl Scolices)

• Sucker like Organs of Scolex
• Bothria with slit-like groove with weak suction
  powers and usually two in number

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Scolex (pl Scolices)

• Sucker like Organs of Scolex
• Bothridia usually in groups of four, quite
  muscular and can be highly mobile and leaf like.

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Neck

• Undifferentiated stem cells that give rise to
  proglottids in strobila.

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Integument

• Microtriches (like Microvilli of vertebrate small
  intestine), on surface of proglottid.
• Absorb nutrients

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Proglottids

• Unique structure of Cestodes
• Contains both male and female organs
• Essentially a whole reproductive package in one
  segment of the strobila.

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RED Male BLUE Female
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Systematics

• Order Pseudophyllidea
• Family Diphyllobothriidae
• Diphyllobothrium latum
• Order Cyclophyllidea
• Family Taeniidae
• Taenia saginata, T. solium, T. multiceps,
• T. hydatigena, T. pisiformis, T.
  taeniaeformis,
• T. ovis
• Echinococcus granulosus
• Family Dilepididae
• Dipylidium caninum
• Moniezia benedeni, M. expansa
• Anoplocephala spp.
• Order Cyclophyllidea
• Family Taeniidae
• Taenia saginata, T. solium, T. multiceps,

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Life Cycles
Definitive Host
Adult
Egg

Coracidium
Intermediate Host
Oncosphere
Cysticercus
Hydatid Cysts
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Diphyllobothrium latumFish tapeworm

• Important parasite of man.
• Definitive hosts can be humans, dogs, foxes,
  cats, mink, bears, and seals. 
• Site of attachment small intestine.
• In humans the tapeworm can reach a length of 10
  meters (gt30 feet) and produce over a million eggs
  a day! .

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Diphyllobothrium latumFish tapeworm

• Dogs and cats are often infected when they are
  fed the offal remaining after cleaning fish.
• Occasionally, humans are infected with the
  plerocercoid stage of of cestodes. Such
  infections are refereed to sparganosis.

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Taenia saginataBeef tapeworm

• Most common tapeworm in humans.
• Large species reaching up to 20 m.
• No hooks on scolex.

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Taenia saginata - Beef tapeworm

• Beef Tapeworms do not cause a serious disease.
• Usually asymptomatic but may cause dizziness,
  abdominal pain, diarrhea, headache and nausea.
• Proglottids obvious in feces.

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Taenia solium
Similar to T. saginata but with hooks on scolex
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Taenia solium
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Taenia solium

• Distinct difference with T. saginata is that
  humans can be infected with egg stage and
  onocosphere migrates to some site in body and
  develops into cycticercus
• This can be serious, called Cysticercosis

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SECTION OF SKELETAL MUSCLE FROM PIG
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Taenia solium

• Most common tissues in order
• Connective tissues
• Eye
• Brain
• Muscles
• Heart
• Liver
• Lungs

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Taenia solium

• When in brain, may cause severe central nervous
  system dysfunction.
• Most common and distinct symptom is sudden onset
  epilepsy.
• Brain imaging can now spot cysticercus in brain.

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Other Taenia spp.

• Taenia multiceps normally found in dogs and
  wolves. Contracted by eating infected parts of
  sheep.
• Taenia hydatigena in sheep.
• Taenia taeniaeformis occurs in domestic and wild
  cats. Little damage to cat but metacestode in
  rodent host causes harm.
• Taenia ovis

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Taenia pisiformis

• Dogs are definitive host
• Rabbits most often serve as the intermediate
  host. 
• .  Dog owners often encounter this parasite when
  the proglottids are passed in the stools of their
  pet. 
• The proglottids of this species are distinctly
  rectangular and much larger than those the more
  common dog tapeworm, D. caninum.

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Echinococcus granulosus

• Smallest tapeworms in Family Taeniidae.
• Normally in small intestine of Canines, as
  definitive hosts.
• Dogs are infected when they eat infected
  herbivores (sheep, goats, camels, reindeer, pigs,
  etc.)
• Occasionally infect humans. The hyatid cysts grow
  very slowly and can overcrowd organs.

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Dipylidium caninum

• Dogs or cats (humans rarely) as the definitive
  host
• Fleas or lice are the intermediate host. 

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Dipylidium caninum

• Flea or louse ingests the eggs in the perianal
  region of the dog or cat. 
• The dog or cat (or human) is infected when they
  ingest a flea or louse infected with the
  metacestode state (cysticercoid)

Dog flea
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Dipylidium caninum
Proglottids of Dipylidium caninum compared to a
match stick.  These are often passed intact in
the feces of an infected dog.  When the
proglottids dry, their appearance is similar to
grains of rice. 

• (The proglottids of the other common tapeworm of
  dogs, Taenia pisiformis, are much larger and
  rectangular in shape.)

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Moniezia expansa

• Sheep are the definitive host and soil mites
  serve as the intermediate hosts. 
• Orobatid mites are infected when they eat the
  eggs from feces the metacestode stage in the
  mite is called a cysticercoid. 
• Sheep are infected when then eat infected mites
• This species of tapeworm is unusual in that each
  proglottid contains two sets of female
  reproductive organs

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Anoplocephala spp.

• Cosmopolitan tapeworms of horses.
• Orobatid mites are intermediate hosts
• Heavy infection can result in death.