Week 5: Cestodes Flashcards by MC GC

Which tapeworm life cycle stage is infective for the intermediate host?

Eggs

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What are the parts of an adult tapeworm?

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What are the parts of a tapeworm egg?

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What kind of tapeworm stages can you use for stool samples?

Proglottids
Whole tapeworms

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Which tapeworm stage can you use for concentration in the lab?

Eggs

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What are the two Taenia species and what are their primary non-human hosts?

Taenia saginata: beef
Taenia solium: pork

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Describe the lifecycle of Taenia species. Include infective and diagnostic stages

Infective stage: Embryonated eggs ingested by human host

Diagnostic stage: Adults in small intestine

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Describe Taenia species’ eggs

Round
30-43 microns
thick cell wall with radial striations
inside of embryonated egg 6-hooked oncosphere (refer to image)

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Which Taenia parts are found in the feces?

eggs
scolex
proglottids (segmented part)

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What is the scolex?

It’s the head of the tapeworm

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Since can’t look at eggs to differentiate between Taenia species, what do you look at instead?

Uterine branches of gravid proglottids. Solium has fewer branches while saginata has more branches

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Identify the genital pores of the proglottid and the Taenia species

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How do you distinguish between the scolex of Taenia solium and saginata?

T. solium has rostellum with a double row of hooklets. But both have 4 suckers

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Which human disease is Taenia solium associated with? Signs/symptoms caused by what?

Cystercosis

Cysticerous stage disseminated throughout body causes muscle, brain, eye, and CNS symptoms

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What are the 2 Hymenolepsis spp?

nana dwarf tapeworm
diminuta rat tapeworm

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Describe the Hymenolepsis nana life cycle. Include infective and diagnostic stages

Infective: embryonated egg ingested by humans in contaminated food, water, or hands. Also embryonated egg in feces is infectious
Diagnostic: Embryonated egg in feces

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Describe Hymenolepsis nana eggs

Oval shaped
30-50 microns
Inner membrane with polar filaments
Oncosphere has 6 hooks

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Describe the Hymenolepsis diminuta life cycle. Include infective and diagnostic stages

Infective stage: Cysticerci in body cavity of insect ingested by rodent or human
Diagnostic stage: Eggs passed in feces

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Describe Hymenolepsis diminuta eggs

Size = 70-85 microns
-Round or slightly oval
Striated outer membrane
Thin inner membrane
Zero polar filaments
Oncosphere has 6 hooks

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Describe the fish tapeworm aka Diphyllobothrium latum life cycle. Include infective and diagnostic stages

Infective stage: Human ingests raw or undercooked, infected fish
Diagnostic stage: Unembryonated eggs passed in feces

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Where is Diphyllobothrium latum found?

Found worldwide where pickled or raw freshwater fish is eaten

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Describe the Diphyllobothrium latum egg

Unembryonated
Operculated (refers to the end of the egg having a lid- or cap-like cover)
Bile stained
Size= 58-76 by 40-50 microns
Knoblike structure on the end opposite the operculum

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Which stages of Diphyllobothrium latum are ID’d for lab diagnosis?

scolex
proglottid
egg

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Does pickling readily kill Diphyllobothrium latum?

No. Does not readily destroy eggs. Cooking does kill the eggs

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What is the animal host of *Echinococcus granulosis*?

Dogs ## Footnote Sorry, Scooby Doo

Describe the life cycle of *Echinococcus granulosis*? **Include infective and diagnostic stages**

- **Infective stage:** Embryonated egg in feces - **Diagnostic stage:** Hydatid cyst in liver, lungs, brain, bone, heart

Which disease is *Echinococcus granulosis*? associated with?

Hydatid cyst disease

What does the *Echinococcus granulosis* larval stage produce? Describe

**Hydatid cysts** Contain fluid, brood capsules, and daughter cysts in which the scolices (plural of scolex) of potential tapeworms are formed. Material inside called **hydatid sand**

What determines hydatid cyst size

The organ it grows in. It'll just keep growing until it can't anymore

What are two types of flukes/trematodes (in reference to their reproductive aspect). Where do they live?

1. **Hermaphroditic adults:** live in intestine, lungs, and liver 2. **Unisexual adults:** live within blood vessels (aka blood flukes)

What is the genus of the blood flukes?

*Schistosoma*

Describe the general trematode life cycle

Ain't no way I'm typing all this :)

Describe the *Paragonimus westermani* life cycle. **Include infective and diagnostic stages**

- **Infective stage:** humans ingest inadequately cooked or pickled crustaceans containing metacercariae (cysts) - **Diagnostic stage:** unembryonated eggs in stool or sputum (cuz they're lung flukes). Harder to find in stool though. Better chance finding them in the lungs

Describe the *Paragonimus westermani* egg

- Size: 80-118 microns by 48-60 microns - oval, flattend operculum - slight shoulders - unembryonated - Thickened area opposite the operculum

Describe the **Fasciolopsis buski** life cycle. **Include infective and diagnostic stages**

- **Infective stage:** Metacercariae on water plant ingested by humans or pigs, causing infection - **Diagnostic stage:** Unembryonated eggs passed in feces.

What is the size of **Fasciolopsis buski** adults?

3-7 microns

Describe **Fasciolopsis buski** eggs

- Size = 130-140 by 80-85 microns - Bile stained - Inconspicuous operculum - Unembryonated - **Identical to *Fasciola hepatica* so report as *Fasciola/Fasciolopsis* **

Describe the *Fasciola hepatica* life cycle. **Include infective and diagnostic stages**

- **Infective stage:** Metacercariae on water plant ingested by human, sheep, or cattle - **Diagnostic stage:** Unembryonated egg passed in feces

Describe *Fasciola hepatica* eggs

- Size= 130-150 microns by 60-90 microns - Unembryonated - Inconspicuous operculum - Identical to *Fasciolopsis buski*

Describe the *Clonorchis sinensis* life cycle. **Include infective and diagnostic stages**

- **Infective stage:** Metacercariae in flesh or skin of fresh water fish are ingested by human host - **Diagnostic stage:** Embryonated eggs passed in feces

Size of *Clonorchis sinensis* adults?

6-17 mm

Describe the *Clonorchis sinensis* egg

- Size - 29-35 microns - Embryonated - Flask shaped - Operculated with *prominent shoulders* (Darrell underlined this part in the slides( - Knob at the end opposite the operculum

Describe the *Metagonimus yokogawai* and *Heterophyes heterophyes* life cycles. **Include infective and diagnostic stages**

- **Infective stage:** Host becomes infected by ingesting undercooked fish containing metacercariae - **Diagnostic stage:** Embryonated eggs each with a fully-developed miracidium are passed in the feces

Describe the *Metagonimus yokogawai* and *Heterophyes heterophyes* eggs (same features)

- Size - 28-39 microns - Embryonated - Operculated with *inconspicuous shoulders* (Darrell underlined in slides) - Vase or flask shaped - Resemble *Clonorchis sinensis* and *Opisthorchis* species

True or false: *Schistosoma* eggs are operculated

False

What is the ONE intermediate blood fluke host?

The snail

How do blood flukes infect humans?

Cercarial penetration of skin

Describe the *Schistosoma* life cycle. **Include infective and diagnostic stages**

- **Infective stage:** cCercariae released by snail into water and free-swimming penetrate human skin - **Diagnostic stage:** Passed in feces (*mansoni, japonicum, and haematobium*) or urine (*japonicum or haematobium*)