2nd lecture of fasciolahepatica by waqas ahmad shams
TRANSCRIPT
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FASCIOLA HEPATICA
By
Waqas Ahmad Shams
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الرحمن الله بسمالرحيم
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Scientific Classification
Kingdom: AnimaliaPhylum: Platyhelminthes
Class: TrematodaSubclass: Digenea
Prder EchinostomidaFamily: Fasciolidea
Genus: FasciolaSpecies:hepitica
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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).
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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 (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
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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.
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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?
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
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Review (Cont’d)
- 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/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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