PHYLUM PLATYHELMINTHES

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PHYLUM PLATYHELMINTHES III. Class Cestoidea
tapeworms E. Order Cyclophyllidae
1. Species with cysticercus metacestode e.
Echinococcus granulosus the hydatid worm
-- worldwide distribution throughout U.S.,
esp. south and west -- most damaging of
all cestodes -- smallest adult
tapeworm, but largest metacestode
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PHYLUM PLATYHELMINTHES III. Class Cestoidea
tapeworms E. Order Cyclophyllidae
1. Species with cysticercus metacestode e.
Echinococcus granulosus 1) Life
cycle DH carnivores, esp. canids IH
herbivore wolf moose coyote
rabbit lion warthog dog sheep
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PHYLUM PLATYHELMINTHES III. Class Cestoidea
tapeworms E. Order Cyclophyllidae
1. Species with cysticercus metacestode e.
Echinococcus granulosus 1) Life
cycle -- adult in small intestines of DH
apolytic
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PHYLUM PLATYHELMINTHES III. Class Cestoidea
tapeworms E. Order Cyclophyllidae
1. Species with cysticercus metacestode e.
Echinococcus granulosus 1) Life
cycle -- eggs get on vegetation eaten by
herbivore IH -- hexacanth oncosphere hatches
penetrates gut ? unilocular hydatid
cyst -- hydatid cyst eaten by carnivore
protoscolices
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Hydatid cysts in herbivores
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PHYLUM PLATYHELMINTHES III. Class Cestoidea
tapeworms E. Order Cyclophyllidae
1. Species with cysticercus metacestode e.
Echinococcus granulosus 2) pathology
zoonosis (humans act as IH) -- accidental
ingestion of eggs -- most common in people
associated with sheep ranching -- hydatid
cysts in liver, lungs, brain
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Hydatid cyst human liver (hepatic hydatidosis)
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Hydatid cysts human brain
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Hydatid cyst removal
Aspiration of hydatid fluid
Bile injected into cyst
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Hydatid cyst removal
Removal of cyst wall repair of cyst cavity
Cyst membrane removed
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PHYLUM PLATYHELMINTHES III. Class Cestoidea
tapeworms E. Order Cyclophyllidae
1. Species with cysticercus metacestode e.
Echinococcus multilocularis -- in
boreal regions -- most common in fur
trappers
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PHYLUM PLATYHELMINTHES III. Class Cestoidea
tapeworms E. Order Cyclophyllidae
1. Species with cysticercus metacestode e.
Echinococcus multilocularis 1) life
cycle -- DH foxes IH
rodents -- metacestode
multilocular (alveolar) cyst
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PHYLUM PLATYHELMINTHES III. Class Cestoidea
tapeworms E. Order Cyclophyllidae
1. Species with cysticercus metacestode e.
Echinococcus multilocularis 2)
Pathology -- accidental ingestion of eggs ?
alveolar cysts in liver, lungs -- in humans,
often no protoscolices misdiagnosed as
cancer -- 75 fatality if untreated --
rare in humans
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PHYLUM PLATYHELMINTHES III. Class Cestoidea
tapeworms E. Order Cyclophyllidae
2. Species with cysticercoid metacestode a.
Hymenolepis nana the dwarf tapeworm --
common human tapeworm, esp. children
(1 southern U.S.
97 Moscow) -- small usually lt 40 mm
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PHYLUM PLATYHELMINTHES III. Class Cestoidea
tapeworms E. Order Cyclophyllidae
2. Species with cysticercoid metacestode a.
Hymenolepis nana the dwarf tapeworm
1) life cycle DH human, rats
apolytic
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PHYLUM PLATYHELMINTHES III. Class Cestoidea
tapeworms E. Order Cyclophyllidae
2. Species with cysticercoid metacestode a.
Hymenolepis nana the dwarf tapeworm
1) life cycle -- eggs eaten
by grain beetle, Tenebrio, or larval flea,
Ctenocephalides (IH optional)
-- oncosphere penetrates gut ? cysticercoid
larvae
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PHYLUM PLATYHELMINTHES III. Class Cestoidea
tapeworms E. Order Cyclophyllidae
2. Species with cysticercoid metacestode a.
Hymenolepis nana the dwarf tapeworm
1) life cycle -- IH eaten by
rat ? cysticercoid becomes adult in gut
-- rat ingests eggs directly ? oncosphere ?
cysticercoid ? invades gut ? adult (rat
DH and IH)
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PHYLUM PLATYHELMINTHES III. Class Cestoidea
tapeworms E. Order Cyclophyllidae
2. Species with cysticercoid metacestode a.
Hymenolepis nana the dwarf tapeworm
2) pathology -- few harmful effects, except
in massive infection -- humans become infected
by accidental ingestion of eggs
? oncosphere ? cysticercoids in gut wall ?
reinvade gut ? adults
ingestion of grain beetle or flea
autoinfection -- treat with Praziquantel
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PHYLUM PLATYHELMINTHES III. Class Cestoidea
tapeworms E. Order Cyclophyllidae
2. Species with cysticercoid metacestode b.
Hymenolepis diminuta
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PHYLUM PLATYHELMINTHES III. Class Cestoidea
tapeworms E. Order Cyclophyllidae
2. Species with cysticercoid metacestode b.
Hymenolepis diminuta DH rat, human IH
Tenebrio
Egg with oncosphere
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PHYLUM PLATYHELMINTHES III. Class Cestoidea
tapeworms E. Order Cyclophyllidae
2. Species with cysticercoid metacestode c.
Dipylidium caninum cucumber seed worm
double-pored tapeworm of dogs and cats
often occurs in children
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PHYLUM PLATYHELMINTHES III. Class Cestoidea
tapeworms E. Order Cyclophyllidae
2. Species with cysticercoid metacestode c.
Dipylidium caninum 1) Life cycle
DH dogs, cats in gut proglottids
with egg capsules apolytic
cucumber seed proglottids
egg capsule
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PHYLUM PLATYHELMINTHES III. Class Cestoidea
tapeworms E. Order Cyclophyllidae
2. Species with cysticercoid metacestode c.
Dipylidium caninum 1) Life cycle
-- eggs ingested by larval
Ctenocephalides ? onchosphere ? penetrates
gut ? cysticercoid in hemocoel
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PHYLUM PLATYHELMINTHES III. Class Cestoidea
tapeworms E. Order Cyclophyllidae
2. Species with cysticercoid metacestode c.
Dipylidium caninum 1) Life cycle
-- flea ingested by DH (dog, cat,
child)
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PHYLUM PLATYHELMINTHES III. Class Cestoidea
tapeworms E. Order Cyclophyllidae
2. Species with cysticercoid metacestode c.
Dipylidium caninum 2) Pathology --
host can develop large numbers of
tapeworms -- typically not very pathogenic
can cause diarrhea -- treatment Praziquantel
for adult worms control fleas
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PHYLUM PLATYHELMINTHES III. Class Cestoidea
tapeworms E. Order Cyclophyllidae
2. Species with cysticercoid metacestode d.
Monezia spp. DH sheep, cattle IH
grass mite (has cysticeroid larva)
?
(cool)
?
!!
Adults in gut
grass mite
proglottids in feces
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PHYLUM PLATYHELMINTHES III. Class Cestoidea
tapeworms F. Order Caryophyllidea --
simple scolex no suckers -- one proglottid
(monozoic)
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PHYLUM PLATYHELMINTHES III. Class Cestoidea
tapeworms F. Order Caryophyllidea --
life cycle DH fish eggs released eaten by
aquatic annelid
procercoid eaten by fish ? adult cestode (no

plerocercoid stage) -- adult cestode may be
neotenic plerocercoid (neotony to achieve
sexual maturity in a juvenile form)