Parasitology > Cestodes > Flashcards

Cestodes Flashcards

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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
Plerocercoid
Second larval stage | - found in 2nd IH
26
Taeniidae
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!)
27
What is the treatment of choice for Taeniidae?
- praziquantel - epsiprantel - fenbendazole (Taenia pisiformis)
28
Taenia pisiformis life cycle
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)
29
Where is the cysticercus located in the IH of Taenia pisiformis?
On the liver/mesentery
30
Taenia hydatigena life cycle
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
31
Taenia taeniaeformis life cycle
DH (felids) --> strobilocercus is digested --> scolex embeds in SI mucosa --> develops into adult --> proglottids shed in feces --> IH (rodents), strobilocercus in liver, peritoneum
32
Taenia multiceps coenurus is located in the ______
Sheep brain
33
Taenia serialis coenurus is located in the _______
Cat brain
34
Which 2 species of Taenia have public health importance?
- Taenia solium (pork tapeworm) | - Taenia saginata (beef tapeworm)
35
Taenia solium life cycle
DH (humans) --> proglottids shed in feces --> IH (swine) cysticercus in muscle --> DH ingests IH, or becomes accidental IH via ingesting eggs
36
Taenia saginata life cycle
DH (humans) --> proglottids shed in feces --> IH (cattle), cysticercus in muscle **no chance of humans becoming accidental IH, ingested eggs do not develop**
37
Taenia solium cysterceri are located in ______
Various locations - subcutaneous, eyes, etc - neurocysticercosis: prevalence of epilepsy
38
Taenia solium and Taenia saginata prevalence
Endemic foci throughout the world - high prevalence of infected pigs - high risk factors for human infection
39
Echinococcus spp
- small adult stages (several mm long, 3-5 segments) - metacestodes are very large! --> unilocular or multilocular hydatid cysts - zoonotic!!
40
Echinococcus granulosus life cycle
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
Echinococcus granulosus - sylvatic cycle
Wolf (DH) --> caribou (IH) --> dingo (DH) --> kangaroo (IH) - other DH: coyotes - other IH: moose
42
Echinococcus granulosus - domestic cycle
Dogs (DH) --> sheep (IH) | - other IH: swine, cattle, horses
43
Distribution of E. granulosus in US
Common in sheep herding areas
44
E. granulosus - zoonosis
Humans are accidental IH - ingest eggs while handling dogs - benign neoplasia, cystic echinococcosis - endemic in Australia, Africa, S. America
45
Echinococcus multilocularis life cycle
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
Echinococcus multilocularis - sylvatic cycle
Arctic fox (DH) --> vole (IH) - other DH: wolves, other foxes - other IH: lemmings, other rodents - sylvatic is the primary cycle!!
47
Echinococcus multilocularis - domestic cycle
- other DH: dogs, cats (rare) | - other IH: rodents (rarely, cattle, horses, swine)
48
E. multilocularis prevalence
Endemic to northern hemisphere
49
E. multilocularis zoonosis
Humans are rarely an accidnetal IH - pathology mimics hepatic carcinoma - alveolar echinococcosis/hydatid disease
50
Diplylidium caninum
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
Dipylidium caninum life cycle
DH (canids, felids) --> proglottids shed in feces --> egg packet --> flea larva ingests eggs --> IH (adult fleas), biting lice --> cysticercoid --> DH ingests flea
52
How do diagnose D. caninum
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
Anoplocephala perfoliata
``` DH: equids - ileum, cecum, ileocecal junction - 4 lappets under suckers - associated with colic, inflammation, ulcers IH: oribatid (free living) mites ```
54
Anoplocephala perfoliata life cycle
DH = equids --> proglottids and eggs shed in feces (eggs in low numbers, segments easily missed) --> egg has pyriform apparatus --> IH = oribatid mite --> cysticercoid
55
Anoplocephala magna
- life cycle similar to A. perfoliata - posterior SI - larger than A. perfoliata, no lappets - relatively harmless
56
Paranoplocephala mamillana
- life cycle similar to A. perfoliata - anterior SI - smaller than A. perfoliata, no lappets - relatively harmless
57
Moniezia life cycle
DH (ruminants) --> proglottids shed in feces (pyriform apparatus) --> IH (oribatid mites) --> cysticercoid
58
Are Moniezia pathogenic?
NO | - very common
59
Thysanosoma life cycle
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
Thysanosoma prevalence
- western north and south america | - mountain areas
61
Spirometra life cycle
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
Spirometra spp
- common in southeastern US (Spirometra mansonoides) | - adult cestodes associated with GI signs in dogs and cats (vomiting, diarrhea, weight loss)
63
Sparganosis
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
What if a cat ingests copepods with the procercoid?
Cat becomes the 2nd IH with development of sparganosis
65
Diphyllobothrium latum life cycle
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
Diphyllobothrium latum prevalence
- distribution: cold climates, northern US
67
D. latum human infection
No or mild clinical disease - acute: GI symptoms - chronic: vitamin B12 deficiency --> nerve degeneration
68
Cyclophyllidean segments
- mesocestoides and echinococcus: tiny proglottids, will not see grossly - dipylidium: proglottids tapered on ends - taenia: proglottids rectangular in shape
69
Adult _____ cestodes are more likely to cause disease
Diphyllobothriidean
70
Which 2 adult cyclophyllideans do cause disease?
- anoplocephala perfoliata | - thysanosoma
71
Pathogenesis of metacestodes in IH depends on ______
- location - size - invasiveness
72
Name of pathogenesis of Diphyllobothriidean metacestodes in 2nd IH
Sparganosis
73
What is NOT a viable form of treatment for cestodes?
Avermectins/milbemycins
74
Control
- flea control (vacuuming) - prevent predator/prey behavior - pasture management to decrease mite populations and contamination by feces with cestode eggs
75
Humans as accidental IH (4)
- echinococcus granulosus - echinococcus multilocularis - spirometra spp (2nd IH or PH) - taenia solium
76
Humans as accidental or normal DH (4)
- dipylidium caninum (accidental) - taenia solium - taenia saginata - diphyllobothrium latum
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