Fluke: Fasciola hepatica Flashcards
What are the final hosts of Fasciola hepatica?
Most mammals, is of greatest significance in sheep and cattle.
What kind of lifecycle do Fasciola hepatica have?
Indirect with an intermediate host.
Is F. hepatica zoonotic?
Yes.
What is the intermediate host of F. hepatica?
Galba truncatula; an amphibious brown snail.
Describe the pathogenesis of F. hepatica
Adults locate in the bile ducts and gall bladder. They have suckers lined by spines to anchor them in place in the bile ducts.
Describe the life cycle of F. hepatica until it is ready to leave the snail
- Eggs leave bile ducts, enter alimentary canal and are excreted in faeces into environment
- Light stimulates embryonation which takes 9 days and induces the hatching of miracidium
- Miracidium are covered in villi which enable it to move through aqueous environments in order to find intermediate host (snail)
- Release enzymes that enable it to bury into the snail
- First develops into sporocyst before redia which migrate to snails pancreas
- Redia develop in cercaria which leave the snail
How long can miracidium survive in the environment?
Can survive for a few hours before they need to find a host.
How long will miracidium reside in snail?
6-7 weeks.
Describe the lifecycle of F.hepatica from the point it leaves the snail
- Cercaria have a tail which enables it to move through the aqueous environment
- Eventually it will lose its tail and form a cyst called a metacercaria
- Metacercaria are ingested by final host and migrate to the intestine
- Exposed to CO2 and bile which triggers hatching of juvenile
- Juvenile burrows through gut wall and makes its way to the liver where burrow through capsule
- Juvenile matures and moves to bile ducts
How long can metacercaria persisit in the environment?
For months over winter but will die in hot summer months.
How long will juveniles spend travelling through liver and how long does it take them to mature?
6-8 weeks travelling through liver parenchyma.
4 weeks to mature.
Name the 3 presentations of liver fluke
Acute, subactute, chronic.
Describe acute infection,
- Dectected autumn/early winter
- Occurs 2-6 weeks post-ingestion
- Caused by necrotic migration of juveniles
- Resulst in liver damage, haemorrhage, sudden death
Describe subacute infection
- Detected late autumn/winter
- Occurs 6-10 weeks post-ingestion
- Caused by juvenile migration and adults in bile ducts
- Results in liver damage, haemorrhagic anaemia, oedema, ascites
Describe chronic infection
- Detected late winter/early spring
- Occurs 4-5 months post-ingestion
- Caused by adults feeding in bile ducts
- Results in progressive loss of condition, emaciation, sub-mandibular oedema, ascites
