Veterinary Parasitology CH5 - Class Cestoda

Study material for Chapter 5 of Diagnostic Parasitology for Veterinary Technicians. For class BIO225 at MWCC.

Phylum Platyhelmenthes (flatworms) contains…

Trematodes and Cestodes

Trematodes and Cestodes are also called what?

Flukes and Tapeworms

True or false: Flatworms are dorsoventrally flattened?

True

What shape are flukes?

Leaf shaped

What shape are tapeworms?

Ribbon-like and segmented into proglottids

The two classes of cestodes are…

Eucestoda (true tapeworms) and Cotyloda (pseudotapeworms)

Anterior end of cestodes is called…

Scolex or head

The four suckers of cestodes are called…

Acetabula

What is the function of the acetabula?

Hold on to intestinal linging

True or false: Cestodes only attach, they do not take blood meals

True

Where do cestodes absorb nutrients from the host intestine?

Through their skin/tegument

Proglottids closted to the next are sexually…

Immature

Proglottids intermediate distance away from the neck are sexually…

Mature

Gravid proglottids furthest away from the neck

Sex organs are old and “spent”, only remaining part is uterus filled with eggs

True or false: Cestodes are hermaphroditic

True

Each proglottid contains…

Both male and female reproductive organs

Cestodes’ sex organs are on what side of their proglottids?

Lateral sides

What is the difference between cross-fertilization and self-fertilization?

• Cross-fertilization: Between two proglottids

• Self-fertilization: Within one proglottid

Gravids contain what stage of egg? What is it called and why?

Larval stage - Hexacanth because it has 6 hooks

Four types of gravid eggs

• Pyriform apparatus: Pear shape innermost layer of 3 egg coverings

• Dipylidium type: Multiple hexacanths in one egg

• Taenia type: Thicker outer shell, hexacanth in egg

• Pseudophyllidean type: Operculum at one end, hexacanth inside

Life cycle of tapeworms

1. Gravids pass in feces into environment​

2. Rupture and release hexacanth embryos (eggs)​

3. Eggs must be swallowed by intermediate host, depending on species can be vertebrate or invertebrate​

4. Develop in intermediate host to larval metacestode stage​

5. Definitive host ingests intermediate host​

6. Juvenile emerges from metacestode state and attaches to intestine, begins to produce strobila​

7. Proglottids have muscles and can move, can find in feces, hair coat or bedding of infected animal

Metacestode forms

• Hydatid cyst: A fluid-filled sac that forms in the body as a result of infection by the tapeworm Echinococcus granulosus

• Cysitcercus: If intermediate host is mammal (rabbit). Example: Taenia pisiformis (dog)

• Coenurus: Multiceps multiceps

• Tetrathyridia: Larval stage of certain tapeworms, resembling an elongated form with an invaginated scolex at one end

• Cysticercoid: If intermediate host is arthropod (flea or mite). Examples: Dipyllidium caninum (dogs and cats), Thysanosoma actinoides (cattle)

Class Cotyloda, also know as…

Pseudotapeworms

What shape are pseudotapeworms?

Long, segmented, flattened, ribbon-like

True or false: Pseudotapeworms have an anterior scolex

True

Pseudotapeworms have 2 slit-like grooves along the length of the scolex called what?

Bothria

What is the function of the bothria?

Helps them attach to intestinal lining

Strobila are made of…

Immature, mature and gravid proglottids

True or false: Pseudotapeworms are hermaphroditic

True

Pseudotapeworms sex organs are located where in proglottids?

Centrally

Pseudotapeworm eggs are operculated, which means…

They have one flat end of the egg that acts as a lid

Where do their operculated eggs exit?

Through uterine pore

Pseudotapeworm gravids tend to…

Drop off in long chains

Lifecycle of pseudotapeworms

1. Operculated eggs pass into environment​

2. If in water, eggs hatch, release ciliated hexacanth embryo—coracidium out of operculum​

3. Must be ingested by first intermediate host, a tiny crustacean copepod​

4. Inside copepod, coracidium becomes procercoid​

5. When copepod is ingested by second intermediate host, a fish, develops into second infective plerocercoid stage​

6. Definitive host is infected by ingesting fish, plerocercoid develops into juvenile worm and attaches to intestinal lining, builds strobili

The common name of Dipyllobothrium latum is what?

Broad fish tapeworm

The common name of Spirometra mansonoides is what?

Zipper tapeworm