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Flashcards in Cestodes- rest of them Deck (24):

What are distinguishing characteristics of the Hymenolepidae family of cestodes?

proglottids are wider than long
mature proglottids only have 3-4 testes
gravid proglottids disintegrate and release eggs in host
intermediate hosts are invertebrates


What are the two Hymenolepidae species that affect humans?

Hymenolepis nana and Hymenolepis diminuta


What is the distribution of Hymenolepis nana?

dwarf tapeworm is worldwide, affects mostly children


What is particular of the Hymenolepis nana hosts?

rodents are reservoir hosts, they do not necessarily require an intermediate host to complete their life cycle


How can Hymenolepis nana be physically distinguished?

has 150-200 proglottids,
scolex has four suckers and a single row of hooks
15-45mm long (small)


What is the distribution of Hymenolepis diminuta?

worldwide, mostly affects children


How can Hymenolepis diminuta be physically distinguished?

20-60cm long (small)
scolex has 4 suckers and no hooks


What are the reservoir hosts of Hymenolepis diminuta?

dogs, cats, any rodents, others


What are distinguishing features of Dipylidium caninum (aka double-pored dog tapeworm)?

proglottids have genital pores on each side
uterus breaks down into egg capsules, each with several eggs. egg capsules released when in external environment
scolex has rostellum with four rows of hooks and four suckers


What are the hosts of Dipylidium caninum?

definitive: dogs, cats, foxes, humans (children)
intermediate: cat/dog flea


What are some defining characteristics of the order Pseudophyllidea?

-scolex has two grooves (bothria), which are slit-like adhesive organs
-separate male and female genital pores, located mid-ventrally on each proglottid
-testes scattered throughout the proglottid
-gravid proglottids remain attached and secrete eggs through the uterine pore


What are the hosts of worms of the order Pseudophyllidea?

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


What is the distribution of the Pseudophyllidea order?

worldwide but more in northern hemisphere
Great Lakes area in North America, Finland in Europe (eat a lot of pickled fish)


What are the definitive hosts for Diphyllobothrium latum (broad fish tapeworm)?

bears (mostly), dogs, cats, foxes, mink, raccoon, walrus, seals, humans
second intermediate host: fish from Great Lakes


What does Diphyllobothrium latum have an affinity for?

B12, have a receptor on their tegument. affects DNA synthesis, fatty acid synthesis, and energy production of host


Describe the characteristics of the Diphyllobothrium latum eggs

oval or ellipsoidal in shape, possibly inconspicuous operculum and a nob at the opposite end, eggs pass in the stool unembryonated


Describe the body morphology of Diphyllobothrium latum

scolex has bothrium, proglottids are wider than long, genital pores are located mid-ventrally


What are the hosts of Spirometra mansonoides?

definitive: dogs, cats, birds, wild carnivores
accidental: humans
first intermediate: copepods and other freshwater crustaceans
second intermediate & reservoirs: birds, reptiles, amphibians


What is the distribution of Spirometra mansonoides?

worldwide, but more human cases in southeast Asian countries. animal cases are endemic in North America


What disease does Spirometra mansonoides infection cause and what does it do?

sparganosis. can either be due to Spirometra mansonoides infection migrating to brain (cerebral sparganosis) or by migration to the eyes (ocular sparganosis)


Which drugs can be used as antihelminthes?

praziquantel, niclosamide, and albendazole.
can be used to kill adults and eggs in one dose, but specifically targets adult worms


What does praziquantel do?

used for flat worms and also trematodes.
increases worm membrane permeability to calcium ions, which causes them to contract and become paralysed. the body can then digest them, so they are not seen in feces


What does niclosamide do?

used specifically for tapeworms, does not affect pinworms or roundworms.
only effective against adult cestodes, thought to block ATP production by uncoupling oxidative phosphorylation


What does albendazole do?

effective against roundworms, tapeworms and flukes. First treatment used in Echinococcus granulosus infections

in the benzimidazole family of drugs. binds beta-tubulin, preventing its polymerization with alpha-tubulin to synthesize microtubules. This causes reduction of glucose uptake and depletes the glycogen stores of the parasite