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{{Taxobox

{{Taxobox

|species            =''Fasciola hepatica

|species            =''Fasciola hepatica

}}

}}

 

Also known as: '''''Liver Fluke

| Also known as:

| '''Liver Fluke

==Introduction==

==Introduction==

''Fasciola Hepatica'' is an hepatic parasite found mainly in ruminants, namely cows, sheep and goats, but also known to affect horses, pigs, deer and man.  It is found Worldwide, and within the UK, with its prevalence ever increasing.  It is responsible for a 10-15% production loss in each infected animal, as it affects meat, milk and wool production, so is of huge economic consequence.

''Fasciola Hepatica'' is an hepatic parasite of the class [[:Category:Trematodes|Trematoda]], found mainly in ruminants, namely cows, sheep and goats, but also known to affect horses, pigs, deer and man.  It is found Worldwide, and within the UK, with its prevalence ever increasing.  It is responsible for a 10-15% production loss in each infected animal, as it affects meat, milk and wool production, so is of huge economic consequence.

''Fasciola Hepatica'' has a definitive ruminant mammalian host and an intermediate molluscan host (indirect life cycle). Within Europe the intermediate host is almost exclusively the amphibious snail ''Lymnaea truncatulata''. The snail habitat is crucial to the survival of the parasite, so wet conditions are favourable to the development and spread of ''Fasciola hepatica''.

''Fasciola Hepatica'' has a definitive ruminant mammalian host and an intermediate molluscan host (indirect life cycle). Within Europe the intermediate host is almost exclusively the amphibious snail ''Galba truncatula'' (previously called ''Lymnaea truncatulata''). The snail habitat is crucial to the survival of the parasite, so wet conditions are favourable to the development and spread of ''Fasciola hepatica''.

[[Image:Fasciola hepatica.jpg|400px|thumb|right|''Fasciola hepatica'' <br> Adam Cuerden 2007, Wikimedia Commons]]

[[Image:Fasciola hepatica.jpg|400px|thumb|right|''Fasciola hepatica'' <br> Adam Cuerden 2007, Wikimedia Commons]]

Development from miracidium into metacercariae takes around 6-7 weeks under favourable conditions, however, this period can be much longer in unfavourable conditions.

Development from miracidium into metacercariae takes around 6-7 weeks under favourable conditions, however, this period can be much longer in unfavourable conditions.

The final host, or the definitive host then ingests the metacercariae from the grass on the pasture, and these pass through the body into the intestine, where they excyst in the wall of the small intestine.  They then travel through the wall of the gut, and migrate into the liver, through the liver parenchyma. The young liver flukes migrate through the liver for around 6-8 weeks before entering the bile ducts. They may also migrate into the gall bladder, where they reach full sexual maturity.

Upon ingestion by the final or definitive host from the grass, metacercariae  excyst to present as immature  flukes in the small intestine. These then migrate across the peritoneal  cavity over a period of roughly one week, and invade the liver. Larvae continue to migrate within the hepatic parenchyma, becoming more destructive as they grow to a length of up to one centimetre. The young liver flukes migrate through the liver for around 6-8 weeks before entering the bile ducts where they mature to adults and begin to produce eggs. They may also migrate into the gall bladder, where they reach full sexual maturity.

The prepatent period of ''Fasciola hepatica'' is 10-12 weeks. In untreated sheep it may survive and continue to infect for many years. In cattle it is usually less than 1 year.

The prepatent period of ''Fasciola hepatica'' is 10-12 weeks. In untreated sheep it may survive and continue to infect for many years. In cattle it is usually less than 1 year.

===Epidemiology===

===Epidemiology===

In temperate areas, there are two superimposed epidemiological cycles, known as the summer and winter infections of the snail. On mainland Britain, the summer cycle predominates as a high proportion of snails perish during the winter, but very occasionally, weather sequences allow the winter cycle to affect the pattern of disease. On the west coast of Ireland, the winter cycle of events determines the timing of clinical outbreaks.

In temperate areas, there are two superimposed epidemiological cycles, known as the summer and winter infections of the snail. On mainland Britain, the summer cycle predominates as a high proportion of snails perish during the winter, but very occasionally, weather sequences allow the winter cycle to affect the pattern of disease. On the west coast of Ireland, the winter cycle of events determines the timing of clinical outbreaks.

==Pathogenesis==

==Pathogenesis==

The severity of the infection is mainly dependent on the number of metacercariae ingested.  The Pathogenesis is often described as two-fold. The first stage occurring when the parasite migrates through the liver parenchyma, causing liver damage and haemorrhage.  The second phase occurs when the parasite is in the bile ducts, and damage is a result of the haematophagic activity of the adult flukes.

The severity of the infection, [[Fasciolosis]], is mainly dependent on the number of metacercariae ingested.  The pathogenesis is often described as two-fold. The first stage occurring when the parasite migrates through the liver parenchyma, causing liver damage and haemorrhage.  The second phase occurs when the parasite is in the bile ducts, and damage is a result of the haematophagic activity of the adult flukes.

 

 

==References==

==References==

   

   

[[Category:Trematodes]]

[[Category:Trematodes]]

[[Category:Liver Trematodes]]

[[Category:Liver Trematodes]]

[[Category:To_Do_-_Max]]

[[Category:Expert_Review - Parasites]]

 

[[Category:Expert_Review]]