Cestodes: Tapeworm

Question 1

Where in the host do adult tapeworms locate?

Answer 1

Attach to gut wall

Question 2

Descrie the pathogenesis of tapeworm

Answer 2

1. Attach to gut wall using suckers and hooks on head. 2. Hooks are in concentric rolls which stops them getting carried away by peristalsis.
2. Segements budded from the neck, mature as pass down body.
3. Segments contain male and female reproductive parts.

Question 3

What is the name given to the head of the worm?

Answer 3

Scolex

Question 4

What is the name given to the segments at the end of the worm?

Answer 4

Gravid - only contain eggs

Question 5

How to tapeworms intake nutrition?

Answer 5

Absorb across surface, don’t have an alimentary tract.

Question 6

Describe the general life cycle of a tapeworm

Answer 6

1. Eggs in the environment are ingested by an intermediate host
2. Egg hatches and embryo released into intermediate host
3. Larvae settle down and encyst in muscle tissue
4. Cysts are ingested by final host
5. Hatch and adults migrate to SI
6. Latching of head to GI wall stimulates worm to start budding
7. Gravid segments shed from the worm and pass out in faeces
8. Faeces contain eggs that are very resistant (can survive in environment for years)

Question 7

What 2 forms can cysts come in?

Answer 7

1. Hydatid - contain many thousands of scoleces, cysts can grow to different sizes in host (can be v big)
2. Cystercercus - contains only 1 scolex, encysts in muscle, commonly seen in abattoir

Question 8

Describe the general pathology of tapeworms

Answer 8

Caused by larval stages encysted in intermediate host. Little pathology caused by adults, although are some exceptions.

Question 9

Name 3 zoonotically important tapeworm species

Answer 9

Taenia saginata, Taenia solium, Echinococcus granulosus

Question 10

What are the 2 hosts of Taenia saginata?

Answer 10

Intermediate - cattle

Final - humans

Question 11

Describe the lifecycle of T.saginata

Answer 11

1. Eggs ingested by bovine
2. Embryo released in abomasum and penetrates SI wall
3. Embryo travels to skeletal muscle and encysts (becomes Cysticercus bovis)
4. Undercooked meat ingested by human
5. Adult worm in human SI
6. Millions of eggs per day are passed in gravid segments in faeces into the environment

Question 12

How is T. saginata diagnosed?

Answer 12

Abattoir. Meat inspection of masseter, heart, tongue, diaphragm, inercostal muscles.

Question 13

How can T. saginata be controlled?

Answer 13

1. Meat inspection
2. Cooking meat >57 degrees to kill cysts
3. Restrict use of agrovert to arable fields/ don’t allow cattle to graze on fields where it has been used for atleast 2 years
4. Good hygiene/sanitation

Question 14

Name the 2 hosts of Taenia solium

Answer 14

Intermediate - humans/pigs

Final - humans

Question 15

Descrive the life cycle of T. solium

Answer 15

Similar to T. saginata except pig replaces cow

Question 16

Describe the pathology of T. solium

Answer 16

Adult tapeworm doesn’t cause any pathology.

Cysts are pathological agents, often found in CNS or eye and can be very serious.

Question 17

Describe the epidemiology of T. solium

Answer 17

1. Occurs where there is close association between man and pig
2. Occurs when pigs have unrestricted access to human waste
3. Poor meat inspection

Question 18

How can T. solium be controlled?

Answer 18

1. Treat humans to kill adult tapeworms
2. Mass treatment of pigs
3. Better meat inspection
4. Better health education

Question 19

What are the hosts of Echinococcus granulosus

Answer 19

Intermediate - sheep, humans can be accidental

Final - dogs

Question 20

Describe the lifecycle of E. granulosus

Answer 20

1. Eggs in environment ingested by IMH
2. Embryo is released and penetrates SI wall
3. Forms hydatid cyst in liver and/or lungs
4. Cyst ingested by FH
5. Adult worms locate in SI of dog
6. Gravid segments containing eggs are shed in faeces

Question 21

Describe the pathogenesis of E. granulosus

Answer 21

1. Cysts usually well tolerated by IMH unless in unusual site
2. Most cases detected in abattoir
3. Adult worms not pathogenic in dog but are in human
4. Pathology generally associated with cystic stage

Question 22

How can E. granulosus be controlled?

Answer 22

1. Regular de-worming of dogs
2. Proper disposal of infected carcasses
3. Good hygiene