Cestodes - Exam Questions Flashcards
What are the 3 regions of the tapeworm body?
- Scolex
- Neck
- Strobila
What are the 2 medically important orders of cestodes?
- Pseudophyllidea
- Cyclophyllidea
When comparing Pseudophyllidea and Cyclophyllidea, how do they differ with respect to their eggs, stages that hatch from the egg, number of intermediate hosts, and the larval stages that occur?
- Pseudophyllidea:
- Eggs –> embryonate in water + infective to
humans that eat fish - Stages that hatch from egg –> Coracidia
- # of intermediate hosts –> 2
- Larval stages –> procercoid larvae +
plerocercoid larva
- Eggs –> embryonate in water + infective to
- Cyclophyllidea:
- Eggs –> infective only to cow
- Stages that hatch from egg -> oncospheres
- # of intermediate hosts –> 1
- Larval stages –> oncosphere + cysticerci
Humans can serve as two types of hosts for cestodes: which type is of greater medical significance and why?
- Humans serve as intermediate hosts
- potentially highly pathogenic - Humans as definitive hosts
- nonpathogenic
What drug treats adult tapeworm infection?
Niclosamide + praziquantel
What is the common name of Diphyllobothrium latum? In what regions of the world does it occur? How large does it get?
- Common name –> broad fish tapeworm
- Occurs worldwide
- Length –> up to 30 feet long
Describe the following structures of D. latum: scolex.
bothria located here –> two longitudinal “sucking” grooves
Describe the following structures of D. latum: uterus
rosette shape
Describe the following structures of D. latum: ovary.
bilobed
Describe the following structures of D. latum: testes.
minute, spherical, numerous
Describe the following structures of D. latum: vitelline glands.
follicular
How does the worm (D. latum) release its eggs?
exit from uterus via uterine pore
What is the first intermediate host in the D. latum life cycle?
crustaceans
What is the second intermediate host in the D. latum life cycle?
small fish
What is the larval stage in the first intermediate host in the D. latum life cycle?
procercoid larvae
What is the larval stage in the second intermediate host in the D. latum life cycle?
plerocercoid larva
What role is played by paratenic hosts in D. latum?
predator fish eats small fish + plerocercoid invades tissue
How do humans become infected with D. latum?
eating uncooked fish
What is the unusual disease associated with adult D. latum infection, and what is the mechanism?
- B12 deficiency
- Megaloblastic anemia
How is infection with D. latum diagnosed?
Unembryonated eggs passed in feces of definitive host
What is sparganosis?
development of plerocercoids of animal cestodes in human tissues
How is sparganosis diagnosed?
biopsy
How is sparganosis treated?
surgical removal of larva
What species typically causes sparganosis?
dogs and cats
In what region of the world is sparganosis a significant problem?
Most common in the orient (East related to Europe)
What is the common name of Taenia saginata?
beef tapeworm
Where does Taenia saginata occur in the world?
worldwide
How big does Taenia saginata? get?
5-10m
What is the intermediate host and what larval stage occurs in T. saginata?
- Intermediate host –> cows
- Larval stage –> oncospheres + cysticerci
What reservoir hosts occur in T. saginata?
none
How do humans typically become infected with T. saginata?
eat infected + uncooked beef
What are the medical consequences of infection with T. saginata?
inflammation + toxic reaction, intestinal discomfort, and fibrosis
Describe the structure of the egg of T. saginata.
oncosphere, inner layer of embryophore, outer layer of embryophore, gelatinous layer, and capsule
Which part of the T. saginata egg is usually missing in fecal specimens?
capsule + gelatinous layer
What is the common name of Taenia solium?
pork tapeworm
Where does T. solium occur in the world?
worldwide
How big does T. solium get?
2-7m
How does the structure of the scolex differ in T. solium and T. saginata?
- T. solium scolex –> armed
- T. saginata scolex –> unarmed
How does the structure of the gravid proglottid differ in T. solium and T. saginata?
- T. solium gravid proglottid –> darker and
more squiggly - T. saginata gravid proglottid –> has an outer
layer/membrane + insides are more
organized and straight across from one side
to another
What is the intermediate host and what larval stage occurs in T. solium?
- Intermediate host –> pig (swine)
-Larval stage –> oncosphere + cysticerci
Are there any reservoir hosts in T. solium?
none
Other than the different intermediate host, what is the major difference between the life cycle T. saginata and T. solium?
Unlike T. saginata –> eggs of T. solium develop into cysticerci in humans if injested –> humans = intermediate host
What are the medical consequences of infection with adult T. solium?
- Cysticercosis –> eggs develop into cysticerci in humans if ingested
Effects:
* Fibrosis surrounding cysticerci –> liver,
muscle, eye, CNS
* Pressure effects
* Severe inflammation if worm dies –> fatal
if in brain
What is the name of the medical condition in which humans are infected with larval T. solium?
neurocysticercosis
What are the medical consequences of neurocysticercosis?
leading cause of epilepsy in the US
Where is neurocysticercosis condition a problem in the US?
Houston, LA
How are infections with adult T. solium (vs. adult T. saginata) diagnosed?
small intestine of humans
What is the common name of Echinococcus granulosus?
dog tapeworm
How big does Echinococcus granulosus get?
3-6mm
What is the definitive host of Echinococcus granulosus?
dogs + other canidae (canines)
What types of animals serve as intermediate hosts in Echinococcus granulosus?
sheep, goats, swine
What larval stage develops in the intermediate host in Echinococcus granulosus?
oncosphere –> unilocular hydatid cyst
How do humans typically become infected with the larval stage of E. granulosus?
humans infected as a result of intimate behavior with dogs (dogs licking face) –> ingestion of egg
Would ingesting uncooked tissue from infected intermediate hosts of E. granulosus be hazardous?
no
What are the pathological effects of a unilocular hydatid cyst?
one of the most pathogenic helminths for humans
How is infection with a unilocular hydatid cyst diagnosed?
hydatid stage in live lungs
What are the infective stage for unilocular hydatid cysts?
embryonated egg in feces
What is unusual about the structure of the mature proglottid and gravid uterus of Dipylidium caninum?
- Mature proglottid –> has 2 sets of ovaries + 2
genital pores - Gravid uterus –> uterus paired w/16-20 radial branches each (which disappear early) + fragments into egg packets
How are infections with Dipylidium caninum contracted?
Ingesting a flea infected with cysticercoid
