Platyhelminthes pt 2

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Platyhelminthes pt 2

• Digene trematodes and tapeworms

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Opisthaptor Ectoparasite One host
Trematoda
Acetabulum endoparasite Mollusc/vertebrate life
cycle
Cestoda
Monogenea
Turbellaria
Free living
Microtriches Scolex Proglottids
Cilia lost from ectoderm (parasitic lifestyle)
Phylum Platyhelminthes
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Di(2)-Gene(birth)

• 2 or more hosts
• Endoparasitic
• No cilia on skin, skin is syncytial
• Life cycle
• Adults in definitive host (a vertebrate)
  reproduce sexually ? eggs in hosts feces
  released into water ? hatch into ciliated larva
  (miricidium) ? snail (intermediate host) ?
  asexual reproduction ? sporocyte ? redia ?
  cercaria released from snail ? metacercaria
  encysts in 2nd intermediate host (or forage in
  some cases) ? ingested by definitive host

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Schistosoma mansoni
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200 million infected worldwide Leading cause of
death of Egyptian men 20-44 years old Adults
live in mesenteric veins, veins associated with
bladder Damage caused by unegested eggs (50
never released) Control clean water, sewage
control, snail reduction Exacerbating factors
poverty ignorance, dams
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Swimmers itch

• Schistosoma sp. that infect ducks, muskrat

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Blackspot disease Uvulifer sp.
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Fasciola hepatica (sheep liver fluke)F.
gigantica (human liver fluke)
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Dicrocoelium dendriticum a bile duct fluke of
ruminants such as sheep, goats, deer, pigs.
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3rd Annual Tri-Sci Athlon
Tuesday November 13th CMU Ballroom
Make a team of 3 4 students sign up on the
poster outside SL 118 by October 16th!!
For more information Tri-Beta Meeting October
2nd 600 SL118 Chem Club Meeting October 3rd
700 HA 405 Or contact Marissa Schafer at
marissaschafer_at_hotmail.com
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Opisthaptor Ectoparasite One host
Trematoda
Acetabulum endoparasite Mollusc/vertebrate life
cycle
Cestoda
Monogenea
Turbellaria
Free living
Microtriches Scolex Proglottids
Cilia lost from ectoderm (parasitic lifestyle)
Phylum Platyhelminthes
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Class Cestoda - Tapeworms

• Obligate endoparasites of vertebrates
• Lack digestive tract
• Have scolex for attachment to host
• Body divided into proglottids
• Each proglottid egg factory with its own ovary
  and testis (make up to 50,000 eggs per
  proglottid)
• Worm hundreds to thousands of proglottids

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General life cycle of tapeworms

• Adult in intestine of definitive host ?
  proglottids break off and pass with feces ? eggs
  released from proglottid ? eaten by intermediate
  host ? oncosphere larva ? intermed host ingested
  by definitive host ? adult develops in intestine

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Tapeworms
Scolex
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Echinococcus granulosis a tapeworm of dogs
dingoes
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Dipylidium caninum
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Beef tapeworm Taenia saginata
Attains a length of 10m
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Ligula intestinalis

• Egg ? copepod (encycts as a procercoid) ? fish
  (encysts as a plerocercoid larva) ? ingested by
  final host ? adult tapeworm in gut of bird