Cestodes (Platyhelminthes)

Question 1

Which is the beef tapeworm?

Answer 1

Taenia saginata

Question 2

describe the lifecycle of Taenia saginata

Answer 2

Adult worms in human (def. host) expels eggs in feces.
Ox (int. host) ingests eggs in pasture.
Thick egg wall digested in duodenum and oncosphere released. Has hooks to bore through gut wall and enters circulation.
Encysts = Cysticercus/Cysticerci in muscle.
Cysticerci ingested in raw beef by human.

Question 3

What allows transmission of Taenia saginata?

Answer 3

human feces contaminating pasture
poor standards of meat inspection
eating inadequately cooked beef

Question 4

What is an oncosphere?

Answer 4

contained in egg

is an embryo with hooks.

Question 5

What is the dog tapeworm?

Answer 5

Echinococcus granulosus

Question 6

example of Hydatid disease

Answer 6

Turkana people of Kenya
v. close relationship with dogs.
Used dogs to bathe, as cleaning maids - transmitted cysts

Question 7

lifecycle of dog tapeworm

Answer 7

1. Adult 3-6mm resides in small int of dog.
2. Proglottids release eggs, passed in feces.
3. Int.host eg sheep ingests eggs, hatch in small int and release oncosphere.
4. Oncosphere penetrates int wall and circulates to lungs and liver. Develops into hydatid cyst.
5. cyst produces protoscoleces and daughter cysts.
6. Dog ingests infected cyst containing organs
7. protoscoleces attach to mucosal wall of small int and develop into adults.

Question 8

Which is pork tapeworm?

Answer 8

Taenia solium

Question 9

lifecycle Taenia solium

Answer 9

1. Adult worm 3-5m in human (def. host), proglottids pass in faeces, eggs released.
2. eggs develop into oncosphere in environment and ingested by pig (Int. host)
3. oncosphere migrates to muscles - forms Cysticercus cellulosae.
4. human eats undercooked pork containing Cysticercus celluosae.

Question 10

What happens if a human eats Taenia solium eggs?

Answer 10

Cysticerci develop in skin and brain

Causes epilepsy and neurocysticercosis

Question 11

What happens if Taenia solium passes from human to human?

Answer 11

Develops as it would in a pig- cysticerci develop in tissues

Question 12

Which is the fish tapeworm?

What are the definitive and intermediate hosts?

Answer 12

Diphyllobothrium latum
Def: Humans, fish eating mammals
Int: Copepods, fish

Question 13

Diphyllobothrium latum lifecycle

Answer 13

1. Unembryonated eggs passed in human feces
2. Eggs embryonate in water
3. Coracidia hatch and get eaten by copepods
4. Proceroids develop inside copepods
5. Copepods ingested by fish and pleroceroid larvae develop.
6. passed on from fish to fish then nhuman ingests raw fish