Cestodes: Tapeworm Flashcards
Where in the host do adult tapeworms locate?
Attach to gut wall
Descrie the pathogenesis of tapeworm
- Attach to gut wall using suckers and hooks on head. 2. Hooks are in concentric rolls which stops them getting carried away by peristalsis.
- Segements budded from the neck, mature as pass down body.
- Segments contain male and female reproductive parts.
What is the name given to the head of the worm?
Scolex
What is the name given to the segments at the end of the worm?
Gravid - only contain eggs
How to tapeworms intake nutrition?
Absorb across surface, don’t have an alimentary tract.
Describe the general life cycle of a tapeworm
- Eggs in the environment are ingested by an intermediate host
- Egg hatches and embryo released into intermediate host
- Larvae settle down and encyst in muscle tissue
- Cysts are ingested by final host
- Hatch and adults migrate to SI
- Latching of head to GI wall stimulates worm to start budding
- Gravid segments shed from the worm and pass out in faeces
- Faeces contain eggs that are very resistant (can survive in environment for years)
What 2 forms can cysts come in?
- Hydatid - contain many thousands of scoleces, cysts can grow to different sizes in host (can be v big)
- Cystercercus - contains only 1 scolex, encysts in muscle, commonly seen in abattoir
Describe the general pathology of tapeworms
Caused by larval stages encysted in intermediate host. Little pathology caused by adults, although are some exceptions.
Name 3 zoonotically important tapeworm species
Taenia saginata, Taenia solium, Echinococcus granulosus
What are the 2 hosts of Taenia saginata?
Intermediate - cattle
Final - humans
Describe the lifecycle of T.saginata
- Eggs ingested by bovine
- Embryo released in abomasum and penetrates SI wall
- Embryo travels to skeletal muscle and encysts (becomes Cysticercus bovis)
- Undercooked meat ingested by human
- Adult worm in human SI
- Millions of eggs per day are passed in gravid segments in faeces into the environment
How is T. saginata diagnosed?
Abattoir. Meat inspection of masseter, heart, tongue, diaphragm, inercostal muscles.
How can T. saginata be controlled?
- Meat inspection
- Cooking meat >57 degrees to kill cysts
- Restrict use of agrovert to arable fields/ don’t allow cattle to graze on fields where it has been used for atleast 2 years
- Good hygiene/sanitation
Name the 2 hosts of Taenia solium
Intermediate - humans/pigs
Final - humans
Descrive the life cycle of T. solium
Similar to T. saginata except pig replaces cow
Describe the pathology of T. solium
Adult tapeworm doesn’t cause any pathology.
Cysts are pathological agents, often found in CNS or eye and can be very serious.
Describe the epidemiology of T. solium
- Occurs where there is close association between man and pig
- Occurs when pigs have unrestricted access to human waste
- Poor meat inspection
How can T. solium be controlled?
- Treat humans to kill adult tapeworms
- Mass treatment of pigs
- Better meat inspection
- Better health education
What are the hosts of Echinococcus granulosus
Intermediate - sheep, humans can be accidental
Final - dogs
Describe the lifecycle of E. granulosus
- Eggs in environment ingested by IMH
- Embryo is released and penetrates SI wall
- Forms hydatid cyst in liver and/or lungs
- Cyst ingested by FH
- Adult worms locate in SI of dog
- Gravid segments containing eggs are shed in faeces
Describe the pathogenesis of E. granulosus
- Cysts usually well tolerated by IMH unless in unusual site
- Most cases detected in abattoir
- Adult worms not pathogenic in dog but are in human
- Pathology generally associated with cystic stage
How can E. granulosus be controlled?
- Regular de-worming of dogs
- Proper disposal of infected carcasses
- Good hygiene
