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Parasitology > Cestodes > Flashcards

Cestodes Flashcards

1
Q

Cestoda

A

Phylum: platyhelminthes

  • acoelomates
  • dorsoventrally flattened
  • segmented
  • monoecious
  • adults in DH small intestine
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2
Q

Are adult cestodes pathogenic?

A

Not usually

- larval stages are pathogenic

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3
Q

Proglottids

A

Cestode segments

  • immature segments are toward the head, as they move over they mature
  • gravid segments are located toward the end, contain eggs
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4
Q

Cestode body

A

Stroblia

- chain of independent reproductive units (proglottids)

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5
Q

Scolex

A

Anterior end of cestode

  • holdfast organ
  • may have specialized attachement organs
  • acetabula (suckers, usually have 4)
  • bothria (2 slits on either side for loose attachement)
  • bothridia
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6
Q

Cestode eggs typically contain the ______

A

First larval stage

- eggs come in various morphologies

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7
Q

Cestodes have an _____ life cycle

A

Indirect!
- DH (predator) with cestode in SI –> proglottids with eggs in feces –> eggs in environment ingested –> IH (prey) with metacestode (larval stage) in tissues –> IH ingested

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8
Q

Which stage is infective to the DH?

A

Metacestode

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9
Q

Does the DH have to be a predator?

A

No, the IH could be free living mites in the environment (how horses get infected)

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10
Q

Cyclophyllidea

A

True cestodes

  • terrestrial life cycle
  • cestode larvae require 1 IH
  • IH: various vertebrates and invertebrates
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11
Q

Diphyllobothriidea

A

Primitive cestodes

  • aquatic life cycle
  • cestode larvae require 2 IH
  • first IH: copepod
  • second IH: fish or non-fish vertebrate
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12
Q

Difference between 2 genera

A

Look at ppt!!

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13
Q

Metacestode

A

Larval cestode in IH

- metacestodes are more often associated with disease than adult cestodes!!

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14
Q

How many metacestodes do cyclophyllideans have?

A

6 types, depends on species!

  • metacestodes that develop into 1 adult DH: cysticercus, strobilocercus, cysticercoid
  • metacestodes that develop into multiple adults in DH: coenurus, unilocular hydatid cyst, alveolar (multilocular) hydatid
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15
Q

How many metacestodes do diphyllobothriideans have?

A

2 stages, depends on IH

  • procercoid develops in first IH
  • plerocercoid develops in second IH
  • each plerocercoid develops into 1 adult cestode!*
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16
Q

Cysticercus

A

Bladder worm

  • small, fluid filled scolex inside
  • ex: Taenia pisiformis
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17
Q

Strobilocercus

A

Fluid filled bladder, but scolex is everted!

  • resembles a cyst in adult animal
  • ex: Taenia taeniaeformis
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18
Q

Cysticercoid

A

Solid, scolex inside

  • cestodes with arthropod IH
  • ex: Dipylidium caninum, Anoplocephalids
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19
Q

Coenurus

A

Multiple larvae attached in cyst

- ex: Taenia multiceps

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20
Q

Unilocular hydatid cyst

A

Cysts in cysts, internal budding

  • thick walled, slow growing
  • ex: Echinococcus granulosus
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21
Q

Alveolar (multilocular) hydatid

A

External budding

  • thin walled, invasive, faster growth
  • ex: Echinococcus multilocularis
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22
Q

Endogenous budding

A

Slow growing

- thick walled

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23
Q

Exogenous budding

A

Fast growing

- thin walled

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24
Q

Procercoid

A

First larval stage

- found in 1st IH

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25
Q

Plerocercoid

A

Second larval stage

- found in 2nd IH

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26
Q

Taeniidae

A

Taenia, Echinococcus

  • DH and IH are mammals!
  • predator/prey
  • adult cestodes in DH small intestine
  • metacestodes in IH may cause disease
  • humans may be DH or dead end IH (zoonotic!)
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27
Q

What is the treatment of choice for Taeniidae?

A
  • praziquantel
  • epsiprantel
  • fenbendazole (Taenia pisiformis)
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28
Q

Taenia pisiformis life cycle

A

DH (canids) cysticercus is digested –> scolex embeds in SI –> develops into adult –> proglottids shed in feces –> IH (rabbit), egg ingested, hatches –> hexacanth embryo migrates to organ –> develops into cysticercus (metacestode)

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29
Q

Where is the cysticercus located in the IH of Taenia pisiformis?

A

On the liver/mesentery

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30
Q

Taenia hydatigena life cycle

A

DH (canids) –> cysticercus is digested –> scolex embeds in SI mucosa –> develops into adult –> proglottids shed in feces –> not as common as T. pisiformis in domestic dogs –> IH (ruminants, swine), cysticercus in peritoneal membranes

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31
Q

Taenia taeniaeformis life cycle

A

DH (felids) –> strobilocercus is digested –> scolex embeds in SI mucosa –> develops into adult –> proglottids shed in feces –> IH (rodents), strobilocercus in liver, peritoneum

32
Q

Taenia multiceps coenurus is located in the ______

A

Sheep brain

33
Q

Taenia serialis coenurus is located in the _______

A

Cat brain

34
Q

Which 2 species of Taenia have public health importance?

A
  • Taenia solium (pork tapeworm)

- Taenia saginata (beef tapeworm)

35
Q

Taenia solium life cycle

A

DH (humans) –> proglottids shed in feces –> IH (swine) cysticercus in muscle –> DH ingests IH, or becomes accidental IH via ingesting eggs

36
Q

Taenia saginata life cycle

A

DH (humans) –> proglottids shed in feces –> IH (cattle), cysticercus in muscle
no chance of humans becoming accidental IH, ingested eggs do not develop

37
Q

Taenia solium cysterceri are located in ______

A

Various locations

  • subcutaneous, eyes, etc
  • neurocysticercosis: prevalence of epilepsy
38
Q

Taenia solium and Taenia saginata prevalence

A

Endemic foci throughout the world

  • high prevalence of infected pigs
  • high risk factors for human infection
39
Q

Echinococcus spp

A
  • small adult stages (several mm long, 3-5 segments)
  • metacestodes are very large! –> unilocular or multilocular hydatid cysts
  • zoonotic!!
40
Q

Echinococcus granulosus life cycle

A

DH (canids) –> hydatid is digested –> scolices embed in SI mucosa –> develop into adults –> eggs in feces –> IH (primarily ungulates), unilocular hydatid cyst in liver, lung, etc

41
Q

Echinococcus granulosus - sylvatic cycle

A

Wolf (DH) –> caribou (IH) –> dingo (DH) –> kangaroo (IH)

  • other DH: coyotes
  • other IH: moose
42
Q

Echinococcus granulosus - domestic cycle

A

Dogs (DH) –> sheep (IH)

- other IH: swine, cattle, horses

43
Q

Distribution of E. granulosus in US

A

Common in sheep herding areas

44
Q

E. granulosus - zoonosis

A

Humans are accidental IH

  • ingest eggs while handling dogs
  • benign neoplasia, cystic echinococcosis
  • endemic in Australia, Africa, S. America
45
Q

Echinococcus multilocularis life cycle

A

DH (foxes, other canids, rare in cats) –> hydatid is digested –> scolices embed in SI –> develop into adults –> Taeniid eggs in feces –> IH (rodents) –> multilocular hydatid cyst in abdominal cavity

46
Q

Echinococcus multilocularis - sylvatic cycle

A

Arctic fox (DH) –> vole (IH)

  • other DH: wolves, other foxes
  • other IH: lemmings, other rodents
  • sylvatic is the primary cycle!!
47
Q

Echinococcus multilocularis - domestic cycle

A
  • other DH: dogs, cats (rare)

- other IH: rodents (rarely, cattle, horses, swine)

48
Q

E. multilocularis prevalence

A

Endemic to northern hemisphere

49
Q

E. multilocularis zoonosis

A

Humans are rarely an accidnetal IH

  • pathology mimics hepatic carcinoma
  • alveolar echinococcosis/hydatid disease
50
Q

Diplylidium caninum

A

Cucumber tapeworm, flea tapeworm, double pored tapeworm

  • DH: felids and canids –> infection by ingestion of infected IH, rarely causes pathology in DH
  • IH: Ctenocephalides felis, other fleas, Trichodectes canis
  • zoonotic*
51
Q

Dipylidium caninum life cycle

A

DH (canids, felids) –> proglottids shed in feces –> egg packet –> flea larva ingests eggs –> IH (adult fleas), biting lice –> cysticercoid –> DH ingests flea

52
Q

How do diagnose D. caninum

A

Based on visualization of characteristic proglottids and/or egg packets in feces

  • usually includes a history of flea ingestion
  • animal can still be infected if on a monthly flea control!
53
Q

Anoplocephala perfoliata

A 
DH: equids
- ileum, cecum, ileocecal junction
- 4 lappets under suckers
- associated with colic, inflammation, ulcers
IH: oribatid (free living) mites
54
Q

Anoplocephala perfoliata life cycle

A

DH = equids –> proglottids and eggs shed in feces (eggs in low numbers, segments easily missed) –> egg has pyriform apparatus –> IH = oribatid mite –> cysticercoid

55
Q

Anoplocephala magna

A
  • life cycle similar to A. perfoliata
  • posterior SI
  • larger than A. perfoliata, no lappets
  • relatively harmless
56
Q

Paranoplocephala mamillana

A
  • life cycle similar to A. perfoliata
  • anterior SI
  • smaller than A. perfoliata, no lappets
  • relatively harmless
57
Q

Moniezia life cycle

A

DH (ruminants) –> proglottids shed in feces (pyriform apparatus) –> IH (oribatid mites) –> cysticercoid

58
Q

Are Moniezia pathogenic?

A

NO

- very common

59
Q

Thysanosoma life cycle

A

Fringed tapeworm
- DH (small ruminants, rarely cattle and deer) –> adult cestodes in bile duct and duodenum –> proglottids shed in feces –> egg packets similar to D. caninum –> IH (booklice or bark lice) –> cysticercoid

60
Q

Thysanosoma prevalence

A
  • western north and south america

- mountain areas

61
Q

Spirometra life cycle

A

DH (felids, bobcat, canids, raccoons) –> eggs shed thru central uterine pore (operculated) –> coracidium (aquatic habitat) –> 1st IH (copepod) –> procercoid –> plerocercoid (sparganum) –> 2nd IH (non fish vertebrates) –> could also be paratenic hosts

62
Q

Spirometra spp

A
  • common in southeastern US (Spirometra mansonoides)

- adult cestodes associated with GI signs in dogs and cats (vomiting, diarrhea, weight loss)

63
Q

Sparganosis

A

When the plerocercoid causes disease

  • humans may become accidental 2nd IH via ingestion of copepod with procercoid, or PH via ingestion or transfer of plerocercoid
  • could be ocular, SC, CNS, auricular, pulmonary
64
Q

What if a cat ingests copepods with the procercoid?

A

Cat becomes the 2nd IH with development of sparganosis

65
Q

Diphyllobothrium latum life cycle

A

DH (canids, felids, humans) –> eggs shed thru central uterine pore –> coracidium (aquatic habitat) –> 1st IH (copepod) –> procercoid –> 2nd IH (freshwater fish) –> plerocercoid –> PH (hosts other than fish)

66
Q

Diphyllobothrium latum prevalence

A
  • distribution: cold climates, northern US
67
Q

D. latum human infection

A

No or mild clinical disease

  • acute: GI symptoms
  • chronic: vitamin B12 deficiency –> nerve degeneration
68
Q

Cyclophyllidean segments

A
  • mesocestoides and echinococcus: tiny proglottids, will not see grossly
  • dipylidium: proglottids tapered on ends
  • taenia: proglottids rectangular in shape
69
Q

Adult _____ cestodes are more likely to cause disease

A

Diphyllobothriidean

70
Q

Which 2 adult cyclophyllideans do cause disease?

A
  • anoplocephala perfoliata

- thysanosoma

71
Q

Pathogenesis of metacestodes in IH depends on ______

A
  • location
  • size
  • invasiveness
72
Q

Name of pathogenesis of Diphyllobothriidean metacestodes in 2nd IH

A

Sparganosis

73
Q

What is NOT a viable form of treatment for cestodes?

A

Avermectins/milbemycins

74
Q

Control

A
  • flea control (vacuuming)
  • prevent predator/prey behavior
  • pasture management to decrease mite populations and contamination by feces with cestode eggs
75
Q

Humans as accidental IH (4)

A
  • echinococcus granulosus
  • echinococcus multilocularis
  • spirometra spp (2nd IH or PH)
  • taenia solium
76
Q

Humans as accidental or normal DH (4)

A
  • dipylidium caninum (accidental)
  • taenia solium
  • taenia saginata
  • diphyllobothrium latum

Parasitology (28 decks)

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