FASCIOLA HEPATICA

By

Waqas Ahmad Shams

الرحمن الله بسمالرحيم

Scientific Classification

Kingdom: AnimaliaPhylum: Platyhelminthes

Class: TrematodaSubclass: Digenea

Prder EchinostomidaFamily: Fasciolidea

Genus: FasciolaSpecies:hepitica

General Information

- Commonly known as liver fluke- A parasitic flatworm

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Fasciola hepatica

Fasciola hepatica, also known as the common liver fluke or sheep liver fluke.

Is a parasitic flatworm of the class Trematoda, phylum Platyhelminthes that infects liver of various mammals, including humans.

The disease caused by the fluke is called fascioliasis (also known as fasciolosis).

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.

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

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

Hosts

- Cattle - Sheep- Sometimes humans

Life Cycle

Life Cycle (Cont’d)

- The adult F. hepatica lives in bile ducts of the host’s 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 (Cont’d)

- 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

Life Cycle (Cont’d)

- 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.

http://www.cdfound.to.it/hTML/fh2a.htm

Four Symptomatic Patterns

- Acute Phase- Cronic Phase- Halzoun- Ectopic Infection

Acute Phase

- Rarely seen in humans- Fever, tender hepatomegaly, and

abdominal pain are frequent symptoms. - Vomiting, diarrhea, and anemia may also

be present

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

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.

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

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

Control Methods

- Education- Molluscicides: application of

malluscicides to decrease the population of Lymnaea snails

- Chemotherapy

Review Questions

- 1. What is the average size of an adult F. hepatica?

a. 20 mm x 5mmb. 30 mm x 13 mmc. 10 mm x 5 mm2. What continent can F. Hepatica be found?a. Africab. Asiac. Americad. All of the above

Review (Cont’d)

- 3. What is the most effective way to treat fascioliasis?

a. bithionol

b. flagyl

c. triclabendazole

References

- “Fascioliasis” Retrieved: 2/19/2007 http://www.stanford.edu/class/humbio103/fascioliasis/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

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