04. Cestodes: Order cyclophyllidea, Family Hymenolepididae Flashcards
What is the taxonomy of H. nana?
Order Cyclophyllidea
FAmily Hymenlopididae
Genus Hymenolepis
Species nana
What is the taxonomy of H. diminuta?
Order Cyclophyllidea
FAmily Hymenlopididae
Genus Hymenolepis
Species diminiuta
What is the common name of H. nana?
dwarf tapeworm
What is the common name of H. diminuta?
rat tapeworm
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
What is the IH of Hymenolepididae family?
an invertibrate is the IH
What are the two species in Family Hymenolepididae that infect humans?
H. nana and H. diminuta
Who is the most common culprit of H. nana?
Children, because they play in dirt and often eat it
Who is a reservoir host for H. nana?
rodents
What is special about H. nana?
They are the only tapeworm that does not need an IH to complete its life cycle
What is the length of H. nana?
- 1.5-4.5 cm in length
- adult has 150-200 prglottids
How many suckers and hooks in H. nana?
- four suckers
- 1 row of hooks
Who is most affected by H. diminuta?
Children, because they play in dirt and often eat it
What is the length of H. diminuta?
20-40 cm in length
How many suckers and hooks in H. diminuta?
- 4 suckers
- NO hooks
What are possible reservoir host of H. diminuta?
- dogs
- cats
- many rodent species
What is the taxonomy of D. caninum?
Order Cyclophyllidea
Family Dipylidiidae
Genus Dipylidium
Species Caninum
What is the common name for Dipylidium caninum?
Double-pored dog tapeworm
Who is the major DH of Dipylidium caninum?
Canine
What makes them a “double pored” worm?
the adult worms have genital pores on either side
What is different about the uterus of D. caninum?
- it breaks down into egg capsules, each containing -
several eggs with oncospheres
How are proglottids/eggs spread?
- it is the gravid proglottids that are passed in feces and the eggs are released in capsules
How many suckers and hooks in D. caninum?
- four suckers
- four rows of hooks
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
