Fasciola hepatica

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Fasciola hepatica

• Sarah Richards
• Max Karpyak

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Scientific Classification

• Kingdom Animalia
• Phylum Platyhelminthes
• Class Trematoda
• Subclass Digenea
• Prder Echinostomida
• Family Fasciolidea
• Genus Fasciola
• Specieshepitica

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General Information

• Commonly known as liver fluke
• A parasitic flatworm

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Geographical Distribution

• Found in Rural areas of temperate and tropical
  regions
• Especially located in regions with cattle and
  sheep herding
• Found on every continent with nearly 180 million
  people at risk and an estimated 2.4 million
  people already infected worldwide.

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Transmission

• Occurs through the ingestion of raw, fresh water
  vegetation
• Plants become exposed to the metacercariae when
  the body of water that the vegetation is growing
  in becomes contaminated by eggs in the fecal
  mater of the infested host
• - A form of infection known as halzoun (in the
  Middle East) is contracted by eating the raw
  liver of an infected animal

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Morphology

• Adult has a flat leaflike body
• About 20-30 mm long by 8-15 mm wide
• Has an anterior elongation where oral and ventral
  suckers are located
• Intestines are very branched

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Hosts

• - Cattle
• Sheep
• Sometimes humans

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Life Cycle
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Life Cycle (Contd)

• The adult F. hepatica lives in bile ducts of the
  hosts liver
• Begin to produce eggs 2-4 months after initial
  infection
• Eggs pass down the bile duct through
  gastrointestinal tract and are released in the
  hosts feces
• Require water of temperature above 10 C to hatch
• The egg hatches and releases miracidiae within
  two weeks
• These newly hatched miracidiae must find a
  Lymanae snail host within 24 of hatching or they
  will die

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Life Cycle (Contd)

• Inside the Lymanaea miracidium loses its cilia
  and develops into a sporocyst
• Each sporocyst develops into a ridia which then
  burst the sporocyst and migrate to the
  hepato-pancreas of the snail
• Ridia then develop into cercariae
• Cercariae attach to plant matter and encyst,
  forming metacercariae which is the infective form
  of the fluke
• Mammalian host consumes the vegetation with the
  metacercariae which then excyst in the small
  intestine

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Life Cycle (Contd)

• Metacercariae burrow through the intestinal wall,
  move through the peritoneal cavity and enter the
  liver parenchyma
• Immature flukes migrate through the liver
  patanchyma for 6-8 weeks giving rise to acute
  symptoms
• Once mature they settle in the bile ducts and
  begin to produce their own eggs after about a
  month.

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http//www.cdfound.to.it/hTML/fh2a.htm
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Four Symptomatic Patterns

• Acute Phase
• Cronic Phase
• Halzoun
• Ectopic Infection

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Acute Phase

• Rarely seen in humans
• Fever, tender hepatomegaly, and abdominal pain
  are frequent symptoms.
• Vomiting, diarrhea, and anemia may also be present

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Cronic Phase

• More common in human population
• Symptoms include bilary cholic, abdominal pain,
  tender hepatomegaly, and jaundice
• In children severe anemia is common
• Inflammation of the bile ducts eventually leads
  to fibrosis and a condition called pipestem
  liver
• Severe infections can lead to death

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Halzoun Ectopic Infection

• Occurs when an individual consumes infected raw
  liver
• The adult worms can cause considerable pain,
  edema, and bleeding that can interfere with
  respiration
• Adults can live in biliary ducts and cause
  symptoms for up to 10 years.

• - In frequent, but can occur in peritoneal
  cavity, intestinal wall, lungs, subcutaneous
  tissue, and very rarely in other locations.

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Diagnostic Tests

• Most widely used form of diagnosis is the
  directly observed presence of F. hepatica eggs
  either in a stool sample, duodenal aspirate or
  biliary aspirate
• Flukes do not begin to produce eggs until about 4
  months after infection, so you cannot test the
  stool
• Prior to 4 months serological tests can be used
• FAST-ELISA (most popular)
• Ultrasound can be used to visualize adult flukes
  in the bile ducts
• CT scan can reveal burrow tracts made by the worms

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Treatment

• Many countries use a 5-10 day course of oral
  bithionol at 30mg/kg body weight
• Triclabendazole is a preferred antihelmintic
  agent, but is unavailable in most countries.
• The resistance is rising to this drug
• Along with pharmaceutical therapy, surgery may be
  necessary in very extreme cases to clear the
  biliary tract

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Control Methods

• Education
• Molluscicides application of malluscicides to
  decrease the population of Lymnaea snails
• Chemotherapy

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Review Questions

• 1. What is the average size of an adult F.
  hepatica?
• 20 mm x 5mm
• 30 mm x 13 mm
• 10 mm x 5 mm
• 2. What continent can F. Hepatica be found?
• Africa
• Asia
• America
• All of the above

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Review (Contd)

• 3. What is the most effective way to treat
  fascioliasis?
• a. bithionol
• b. flagyl
• c. triclabendazole

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References

• Fascioliasis Retrieved 2/19/2007
  http//www.stanford.edu/class/humbio103/fasciolias
  is/Fasciola.htm
• Fasciola hepatica. Wikipedia, free
  encyclopedia. Retrieved 2/19/2007
  http//en.wikipedia.org/wiki/Fasciola_hepatica
• Fasciola hepatica. Retrieved 2/19/2007
  http//www.cdfound.to.it/html/fas1.htm