Parasitology Lec 9: Part 3 platyhelminthes

What is the topic of the handwritten page?

Aquatic invertebrate sampling.

Where should sampling occur?

More shady, undisturbed areas.

How long do artificial substrates need to be in place?

6–8 weeks.

What is one artificial substrate sampler?

Multi-plate sampler.

What is the Ohio multi-plate sampler called?

Hester-Dendy.

What is another artificial substrate sampler?

Rock basket.

What type of sampling uses artificial substrates?

Quantitative sampling.

What is one kick-netting method?

Multi-habitat sampling.

What type of sampling is multi-habitat sampling?

Qualitative sampling.

How can kick-netting be made quantitative?

A 7.5-minute kick.

What conditions should be sampled when kick-netting?

Aerobic conditions.

What should you wear while kick-netting?

Boots to protect toes.

What should you do to sediment while kick-netting?

Shift sediment.

Where must a sampler be placed in relation to flow?

Downstream of flow.

What substrates should be picked?

Rocks, leaves, detritus, etc.

What organisms can be collected by picking substrates?

Black flies.

What organisms are partial to picking substrates?

Midges.

What is a pool?

Slow water.

What is a riffle?

Fast-moving, erosional water.

What is a run?

A fast-moving portion.

What type of sediment occurs in a pool?

Depositional sediment.

Why use all three sampling methods?

You should be able to get all the habitats.

What is the topic of Lecture 9?

Class Cestoda – Tapeworms.

What do tapeworms primarily parasitize?

Vertebrates.

What type of tegument do tapeworms possess?

A nonciliated syncytial tegument.

What digestive structures do tapeworms lack?

No mouth or digestive system.

How do tapeworms receive nutrients?

All nutrients must be received across the tegument.

What attachment structures are on the scolex?

Hooks and/or suckers.

What are the hooks and suckers on the scolex used for?

To maintain the tapeworm’s position within the host.

What is the region posterior to the scolex called?

The neck.

What does the neck produce?

The proglottids.

What reproductive systems does each proglottid contain?

Both male and female reproductive systems.

What is the hydatid dog tapeworm?

Echinococcus granulosus.

What two pathways does the hydatid dog tapeworm have?

A sylvatic and pastoral pathway.

What does sylvatic mean?

Occurring in or affecting wild animals.

What does pastoral mean?

Related to the grazing of sheep or cattle.

Where does adult E. granulosus reside?

In the small intestine of the definitive hosts: dogs, wolves, and coyotes.

What do gravid proglottids release?

Embryonated eggs that are passed in the feces.

What happens after a suitable intermediate host ingests an E. granulosus egg?

The egg hatches in the small intestine and releases an oncosphere.

What are sylvatic intermediate hosts for E. granulosus?

Moose, deer, bison, etc.

What are domestic intermediate hosts for E. granulosus?

Sheep, goat, swine, cattle, horses.

What does an E. granulosus oncosphere do?

Penetrates the intestinal wall and migrates through the circulatory system into various organs, especially the liver and lungs of the intermediate host.

What does an E. granulosus oncosphere develop into in organs?

A hydatid cyst that enlarges gradually, producing protoscolices that fill the cyst interior.

How does the definitive host become infected with E. granulosus?

By ingesting the cyst-containing organs of the infected intermediate host.

What happens after protoscolices are ingested?

They attach to the intestinal mucosa and develop into the adult stage.

Which host does the hydatid dog tapeworm usually cause more problems for?

The intermediate hosts.

What are humans in the E. granulosus life cycle?

A dead-end host.

Where can hydatid cysts occur in humans?

In the liver, heart, or nervous system.

How large can hydatid cysts become?

The size of a basketball, thus disrupting organ function.

What is the dog tapeworm?

Dipylidium caninum.

What animals are the most common definitive hosts of Dipylidium caninum?

Dogs, foxes and cats (and wild felids).

How is Dipylidium caninum easily controlled?

With medicine.

What is the intermediate host of Dipylidium caninum?

The flea.

How can humans become a host for Dipylidium caninum?

In the rare case of swallowing a flea.

How do gravid Dipylidium proglottids leave the definitive host?

Passed intact in the feces or emerge from the perianal region of the definitive host.

What do Dipylidium proglottids typically release?

Proglottids.

What can happen to Dipylidium proglottids on some occasions?

The proglottids rupture and egg packets are seen in feces.

What happens after a dog or cat flea ingests Dipylidium eggs?

A flea, an oncosphere is released into the flea’s intestine.

What does a Dipylidium oncosphere do in the flea?

Penetrates the intestinal wall, invades the insect’s hemocoel (body cavity), and develops into a cysticercoid larva.

How does the flea host become infected by Dipylidium?

By ingesting the adult flea containing the cysticercoid.

What happens in the small intestine of the vertebrate host?

The cysticercoid develops into the adult tapeworm and reaches maturity.

What is the rabbit (dog) tapeworm?

Taenia pisiformis.

What animals are the definitive hosts of Taenia pisiformis?

Dogs, foxes and coyotes.

What animals are the intermediate hosts of Taenia pisiformis?

Rabbits, hares and rodents.

How are Taenia pisiformis proglottids released?

Passed out with the feces.

What happens to Taenia pisiformis eggs?

The eggs become attached to grass and are ingested by the intermediate host.

What happens after a Taenia pisiformis egg hatches?

The egg hatches in the small intestine and the oncosphere burrows through the intestinal wall and travels to the liver via the blood.

What does the Taenia pisiformis cysticercoid do?

Develops in the liver and then burrows out into the peritoneal cavity where it attaches to the viscera.

What happens when a dog eats a rabbit containing a Taenia pisiformis cysticercoid?

The protoscolex attaches to the small intestinal wall of the canid and the worm begins to form proglottids.

What is Moniezia?

A genus of parasitic tapeworms that use sheep, cattle and wild ruminants as definitive hosts.

What is the most important Moniezia species?

Moniezia expansa.

What animals do Moniezia tapeworms not affect?

Dogs, cats, horses, swine, poultry or humans.

Where do adult Moniezia tapeworms reproduce?

In the small intestine.

What are the intermediate hosts for Moniezia?

Oribatid mites.

What happens when oribatid mites ingest Moniezia eggs?

The eggs hatch in their gut and develop into cysticercoids in the body cavity of the mites.

What habitats do oribatid mites prefer?

Humid pastures.

What conditions do oribatid mites avoid?

Light and dryness.

How long can cysticercoids survive inside mites?

For months.

How does the definitive host become infected with Moniezia?

After ingesting contaminated mites while grazing.

What happens to mites after the definitive host ingests them?

The mites are digested and this releases the cysticercoids which attach to the host’s intestinal wall.

What do Moniezia cysticercoids develop into?

Adult tapeworms within several weeks.

How do Moniezia infections affect adult livestock?

They are rather benign and usually do not cause clinical signs.

How can Moniezia negatively affect productivity?

They compete for nutrients with the host.