04. Cestodes: Order cyclophyllidea, Family Hymenolepididae Flashcards by Liz Siciliani

What is the taxonomy of H. nana?

Order Cyclophyllidea
FAmily Hymenlopididae
Genus Hymenolepis
Species nana

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What is the taxonomy of H. diminuta?

Order Cyclophyllidea
FAmily Hymenlopididae
Genus Hymenolepis
Species diminiuta

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What is the common name of H. nana?

dwarf tapeworm

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What is the common name of H. diminuta?

rat tapeworm

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What are the characters of Family Hymenolepididae?

Proglottids that are wider than they are long
mature proglottids contain a small number of eggs
gravid proglottids disintegrate in host and release eggs
3-4 testes

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What is the IH of Hymenolepididae family?

an invertibrate is the IH

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What are the two species in Family Hymenolepididae that infect humans?

H. nana and H. diminuta

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Who is the most common culprit of H. nana?

Children, because they play in dirt and often eat it

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Who is a reservoir host for H. nana?

rodents

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What is special about H. nana?

They are the only tapeworm that does not need an IH to complete its life cycle

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What is the length of H. nana?

1.5-4.5 cm in length

- adult has 150-200 prglottids

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How many suckers and hooks in H. nana?

four suckers

- 1 row of hooks

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Who is most affected by H. diminuta?

Children, because they play in dirt and often eat it

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What is the length of H. diminuta?

20-40 cm in length

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How many suckers and hooks in H. diminuta?

4 suckers

- NO hooks

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What are possible reservoir host of H. diminuta?

dogs
cats
many rodent species

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What is the taxonomy of D. caninum?

Order Cyclophyllidea
Family Dipylidiidae
Genus Dipylidium
Species Caninum

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What is the common name for Dipylidium caninum?

Double-pored dog tapeworm

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Who is the major DH of Dipylidium caninum?

Canine

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What makes them a “double pored” worm?

the adult worms have genital pores on either side

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What is different about the uterus of D. caninum?

it breaks down into egg capsules, each containing -

several eggs with oncospheres

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How are proglottids/eggs spread?

it is the gravid proglottids that are passed in feces and the eggs are released in capsules

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How many suckers and hooks in D. caninum?

four suckers

- four rows of hooks

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What is the taxonomy os S. mansonoides?

Order Pseudophyllidean 
Genus Spirometra (previously Diphyllobothrium)
Species mansonoides

What is special about D. latum and S. mansonoides worms?

they contain some of the largest tapeworms known, with lengths of around 10 m

What are the characteristics of the order Pseudophyllidean?

- scolex contains 2 grooves (aka bothria) - male and female genital openings are separated, and located mid-ventrally in the mature proglottid - proglottids are not shed, rather shed eggs directly into the gut via a uterine pore

What are bothria? what is their functions

- slit-like organs for adhering to the intestine of the host | - they pinch the intestinal wall of the host to hold the worm in place

Why is the life cycle of order pseudophyllidean complex?

because there are 3 or more hosts

What are the hosts of order pseudophyllidean?

first intermediate host: copepod second intermediate host: fish/amphibian DH: fish-eating mammal

What are examples of fish that can be the second intermediate hosts of worms of the order pseudophyllidean?

Minnow, northern pike, perch, salmon, trout

Where are human infections common of worms of the order pseudophyllidean?

the Great Lakes region of North America and in Northern Europe, particularly in Finland (many freshwater lakes, and common practice to eat pickled fish; doesn't kill the parasites)

What is the common name of Diphyllobothrium latum?

Broad fish tapeworm - Broad - proglottids - fish - DH is infected by eating fish

What are common DH of D. latum?

Bears, dogs, cats, foxes, mink, racoons, walruses, seals and humans

What does D. latum have a unique affinity for? Why is this important clinically?

Vitamin B12, because it will affect the cellular metabolism in the infected host

Why are bears a common DH of D. latum?

They eat fish

Why is D. latum found in cats and dogs?

they may eat uncooked scraps of fish

Humans can also become infected with D. latum. How?

by eating raw or undercooked fish

What is the morphology of D. latum eggs?

- The are oval of ellisoidal - Range in size from 55-75 µm by 40-50µm - operculum (can be difficult to see) - small knob at the other end

What is different about the eggs passed in stool of D. latum?

They are unembryonated, become embryonated in water

What is the morphology of the adult D. latum?

- scolex has 2 slit-like grooves (bothria) - proglottids are wider than they are long - genital pores are mid-ventral - longest tapeworm in humans averaging 10m

What is the disease caused by Spirometra mansonoides?

Sparganosis

What are some DH of S. mansonoides?

dogs, cats, birds, and wild carnivores, humans are accidental hosts

What is the first IH of S. mansonoides?

Copepods and other freshwater crustaceans

What are the second IH hosts of S. mansonoides?

birds, reptiles, and amphibians

Where are the most common cases of sparginosis in non-human animals?

North america

What is the life cycle of order cyclophyllidea (summary)

Basic life cycle, usually 2 hosts; H. nana does not require 2 due to autoinfection

What is the life cycle for cestodes using a vertibrate as an IH? (summary)

Embryonated egg (with oncospere) –> cysticercus (IH) –> adult tapeworm (DH)

What is the life cycle for cestodes using an invertibrate as an IH? (summary)

Embryonated egg (with oncospere) –> cysticercoid larvae (IH) –> adult tapeworm (DH)

What is the life cycle of order pseudophyllidean? (summary)

- 3-4 hosts - Unembryonated egg (with developing oncosphere) –> coracidium (free-living in water) –> plercercoid larvae (1st IH) –> plerocercoid (2nd IH) –> adult tapeworm (DH)

What stage is usually killed most effectively by anthelminthic drugs?

The adult stage + the eggs inside it

What is the possible mode-of-action of Praziquantel?

Thought to increase membrane permeability to calcium ions - indices contraction of the parasite, resulting in paralysis

Are tapeworms visible once the host is treated by Praziquantel?

No, the worms are digested. Parts of the worm can be found in feces

What else is Niclosamide used to control?

snail populations in schistosomiasis control campaigns

What life stage is susceptible to Nicloamide?

adult forms, not juvenile forms

What is the possible mechanism of action of Niclosamide?

Thought to possible block ATP production by uncoupling oxidative phosphorylation in the tapeworm

What is Albendazole used for?

it is a broad spectrum anthelminthic, effective against cestodes, trematodes and nematodes

Where was Albendazole developped? When?

SmithKline Animal Health Laboratories in 1972

What category of drugs is Albendazole?

Benzimidazole

How do benzamidazoles work?

Bind to β-tubulin, preventint its polymerization with α-tubulin to form microtubules