FASCIOLA HEPATICAMUZAFFAR KHAN ALAM KHANStudent of TSMU

A Parasite is an organism that spends a significant portion of its life in or on the living tissue of a host organism & which causes harm to the host without immediately killing it. Every free-living species has its own unique species of parasite, so the number of parasitic species greatly exceeds the number of free living species.

PARASITOLOGY & MEDICAL PARASITOLOGY:• It is the study of parasites, their hosts & the relationship between them.

• One of the largest fields in parasitolgy, medical parasitology is the subhect which deals with the parasites that infect humans, the diseases caused by them, clinical picture and the response generated by humans against them. It is also concerned with the various methods of their diagnosis, treatment & finally their prevention & control.

Scientific ClassificationKingdom: Animalia

Phylum: PlatyhelminthesClass: TrematodaSubclass: DigeneaOrder: EchinostomidaFamily: FasciolideaGenus: FasciolaSpecies: hepatica

TREMATODES-FLAT WORMS(FLUKES)• Opisthorchis

• O. sinensis• O. felineus• O. viverini

• Paragonimus• P. westermani• P. kellicotti

• Echinostoma

• Schistosoma• S. mansoni• S. hematobium• S. japonicum

• Fasciolopsis • Fasciolopsis buski• Fasiola • Fasiola hepatica• Fasiola gigantica

Trematodes: Morphological Features• Mouth connects to pharynx,

leads to esophagus, bifurcates into 2 ceca

• No anus: releases cecal contents back through mouth into tissue it infects

• Cecal contents can be seen in histopathologic section and are colloquially referred to as “fluke puke”

• Also possess and acetabulum, or ventral sucker – holdfast organ not associated with feeding

• Near anterior end, mouth is surrounded by muscular oral sucker

Trematodes: Reproduction• With exception of

schistosomes (blood flukes) all flukes are hermaphroditic

• Each fluke possesses both sex organs

• Self-fertilization usually takes place, but cross-fertalization can also occur

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).

• F. hepatica is world-wide distributed and causes great economic losses in sheep and cattle.

• Definitive host:• Sheep• Cattle• Humans (Accidental)• Other Mammals

• Intermediate host:• Fresh Water Snail

• Geographic Range:• Cosmopolitan; anywhere sheep and cattle are

raised

Morphology of adult Fasciola hepatica

acetabulum

Morphology: (Angus, 1978)Specie Size Shape

F.hepatica 5cm length/1.5cm wide

Leaf shape with prominent shoulders

F.gigantica 7.5cm length/1.2cm wide

Leaf shape with scarcely perceptible shoulders

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Life cycle outside the animal • Eggs hatch in spring (>10 °C) to release

miracidia which must penetrate a mud snail (Lymnaea [syn. Galba] truncatula) within 3 hours

• Develop inside snail • Cercariae emerge from snail • Encyst on grass (metacercariae) • Infection of a snail with one miracidium can

produce over 600 metacercariae

Life cycle inside the animal

• Once ingested metacercariae excyst in SI and immature fluke migrate through the gut wall to penetrate the liver

• Tunnel through liver for 6-8 weeks before entering bile ducts where they reach maturity

• Time from infection of cattle/sheep to adult egg-laying fluke is 10-12 weeks

• Little or no development of immunity

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Cycle of Events in Fasciola hepatica• The life cycle of Fasciola hepatica starts when a female lays eggs in the liver of an infected human. Immature eggs are discharged in the biliary ducts and taken out in the feces. If landed in water, the eggs become embryonated and develop larvae called miracidia. A miracidium invades an aquatic snail and develops into cercaria, a larva that is capable of swimming with its large tail.

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• The cercaria exits and finds aquatic vegetation where it forms a cyst called Metacercariae. A human eats the raw freshwater plant containing the cyst. The Metacercariae excysts in the first part of the small intestine, duodenum. It then penetrates the intestinal wall and gets into the peritoneal cavity.

Cycle of events in infection

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Cycle of events in infection• It finds the liver and starts eating liver cells. This happens only a few days after the initial contact with the parasite. Usually the larva spends a few weeks just browsing and eating the liver. Then it relocates to the bile duct where it begins its final stage and becomes an adult. It takes about three months for the Metacercariae to develop into an adult. Adults are about 3 cm long and 1 cm wide. Adult females can produce up to 25000 eggs per day.

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• Ingestion Metacercariae

• Ex-cyst in Duodenum

• Burrows through Intestinal Wall

• Enters Peritoneal Cavity

• Migrates to Liver

Progress of Infection

MACROSCOPIC & MICROSCOPIC EXAMINATION

Egg capsule with emerging miracidium of Fasciola

hepatica.  400x

F.hepatica, egg: eggs measure 140 by 80 µm and are operculated. The colour is yellow to brown. (Formol-ether concentration).

egg capsule with emerging miracidium of Fasciola hepatica.  400x

unembryonated egg capsule of F. hepatica. earlier stage of development.  400x

embryonated egg capsule of Fasciola hepatica.  So-named because the miracidium is fully formed and ready to emerge.  The operculum can be seen to the left.  400x

Redia and cercaria of Fasciola hepatica

Miracidium of Fasciola hepatica. This ciliated, non-feeding larval stage, has about 24 hours to find its specific snail host, such as Fossaria modicella or Stagnicola bulimoides.  400x

The ova

Length 130-145 µmWidth 70-90 µmRegular ellipseThin shellOperculum at one poleGranular yellowish-brown contents filling whole egg

The Adult• one of the largest flukes in the world. • 20 -30mm in length and 13 mm in

width • Leaf shape characteristic with the

anterior end broader than the posterior end and an anterior cone-shaped projection.

• Possesses a powerful oral sucker at the anterior cone and a ventral sucker at the base of the cone attach to the lining of the biliary ducts.

• monoecious - possesses ovaries and testes which are highly branched and allow for individual flukes to produce eggs independently.

A stained adult Fasciola hepatica; approximate length = 20 mm.  The internal organs are highly branched, thus making it very difficult to differentiate the various internal organs

All of their major systems are branched, including the intestine, testes, and ovary.

F.hepatica, adult worm, macroscopic examination: adults measure 2-5 cm by 8-13 mm, are flat, oval in shape with a cephalic cone containing the oral sucker.The adults live in biliary ducts for up to 10 years.

Fasciola hepatica, living adult in bile duct of sheep.

F.hepatica, adult worm, liver biopsy: after excistation in the small intestine, metacercariae penetrate the intestinal wall and the Glisson capsule, cross the liver parenchima to the bile ducts.Eggs can be found in faeces 3-4 months after penetration.

F.hepatica, adult worm, macroscopic examination: higher magnification: particular of the cephalic cone with the oral sucker.

SYMPTOMS:

• The first stage: prepatent or larval period:• Abdominal Pain• Fever• Backache, headache• Chills• Weight loss• Urticaria• Eosinophilia, elevation of AST, ALT• Cough and chest discomfort

• The second stage: patent or biliary period:• Intermittent right upper quadrant pain• Enlarged, tender liver• Diarrhea• Eosinophilia

• Complications: • Anemia, cholangitis, biliary obstruction, subcapsular liver hematomas, hemoperitoneum

Symptoms

Condemned LiverAnnual condemnation of livers of 3-4% of cattle at $3-5 each due to parasites.

•Adult-Biliary hyperplasia, dilatation, fibrosis, calcification•Migration-Diffuse fibrosis, shrunken ventral lobe

• The course of infection passes through three phases:

• The acute phase

• The chronic phase

• The obstructive phase

• Pathology / clinical manifestations are related to the phase

• Acute Phase: • Rarely seen in humans and occurs only when

a large number of metacercariae are ingested at once.

• Fever, tender hepatomegaly, and abdominal pain are the most frequent symptoms of this stage of infection

• vomiting, diarrhea, urticaria (hives), anemia, may be present.

• Caused by the migration of the F. hepatica larvae throughout the liver parenchyma.

• The larvae penetrate the liver capsule and begin to produce symptoms 4-7 days after ingestion.

• Migration and acute phase continues for 6-8 weeks until the larvae mature and settle in the bile ducts.

The acute phase:• Coincides with migration of

the immature flukes through the peritoneal cavity, penetrating liver capsule then through

liver parenchyma till they reach the bile ducts.

liver

Symptoms :

• Acute symptoms

• Asymptomatic (unusual)

• Severe illness

(prostration & jaundice)

(unusual)

• Acute dyspepsia• Prolonged high fever• Hepatomegaly/ abdominal pain in the right hypochondrium•Urticaria•Peripheral eosinophilia, up to 80%.•Anaemia

Cont..• Chronic Phase:

• more common in human • include biliary cholic, abdominal pain, tender

hepatomegaly, and jaundice. • In children, severe anemia - common result of

infection• biliary obstruction and inflammation caused

by the presence of the large adult worms and their metabolic waste in the bile ducts.

• Inflammation of the bile ducts leads to fibrosis and a condition called "pipestem liver", (white appearance of the biliary ducts after fibrosis).

• The final outcome portal cirrhosis and even death.

• The chronic phase, coincides with the presence of the flukes in the bile ducts

• The life span of the parasite is 10-13 years

• Pathology tends to be mild

Symptoms : • Asymptomatic

Few gastrointestinal symptoms• Intermittent fever with persistent

prominent eosinophilia Recurrences of the acute signs & symptoms

Recurrent cholangitis

Obstructive phase

(heavy / prolonged infection)

Coincides with epithelial changes in the bile ducts due to irritation of the epithelium by the spines& the activity of

proline

Diagnosis

Fasciola is diagnosed by fecal sedimentation examination

Eggs are large, operculated and golden in color

DIAGNOSIS:

Laboratory diagnosis• The definitive and most widely used form of diagnosis is the directly

observed presence of Fasciola hepatica eggs either in a stool sample, duodenal aspirate or biliary aspirate.

• However, the flukes do not begin to produce eggs until roughly 4 months after infection.

• Until this time and in the case of ectopic infections where eggs are not present in the stool, serological tests can be used, the FAST-ELISA being the most popular.

• It has a sensitivity of 95% and can detect specific F. hepatic antibodies as early as 2 weeks after infection .

• Ultrasound can be used to visualize the adult flukes in the bile ducts

• CT scan may reveal the burrow tracts made by the worms and dilation of the bile ducts.

Computed tomography (CT) and magnetic-resonance-imaging (MRI)are used for further characterization of the lesion.They are indispensable for the evaluation of extrahepatic affection in AE and they are used for a preoperative evaluation.CT best depicts the typical calcifications and it is used for follow-up examinations at longer intervalls. For serology an ELISA was established based on the purified E.multilocularis carbohydrate antigen Em2 (derived from the laminated layer). It is the reference test for diagnosis and it may allow discrimination of AE from E.granulosus infection.However, in a significant percentage of cases the two species can not be differentiated simply by serological means.

• Halzoun : worm settles in the pharynx. • Occurs when an individual consumes infected

raw liver The young adult worms then attach themselves to the pharyngeal mucosa causes considerable pain, edema, and bleeding that can interfere with respiration.

• The adults can live in the biliary ducts, causing symptoms for up to 10 years.

• Ectopic Infection: Ectopic infections through normal transmission are infrequent but can occur in the peritoneal cavity, intestinal wall, lungs, subcutaneous tissue, and very rarely in other locations.

Fasciola hepatica: although direct diagnosis by observation of eggs in faecal smears it the reference method, indirect diagnostic tests such as IF may allow diagnosis when direct observation is negative. Immunodiagnosis by indirect mmunofluorescence. Antigen: frozen sections of Fasciola hepatica.

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epidemiology• Infection begins when Metacercariae infected aquatic vegetation is eaten or when water containing Metacercariae is drunk. Humans are often infected by eating watercress. Human infections occur in parts of Europe, northern Africa, Cuba, South America, and other locales. It is one of the most important disease agents of domestic stock throughout the world and shows promise of remaining so for years to come.

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Treatment• Bithional

• Highly Effective• Large Dose• High Cost• Long Treatment Period

• Triclabendazole• Easier to Use• 1-2 Oral Doses in 24 hrs• Virtually 100% Effective

• Surgery

Prevention• The presence of a substantial reservoir - keep domestic

animal herds separate from the growing sites of aquatic. This limits the risk of contaminating the vegetation and thus decreases both human infection and the animal reservoir

• The presence of the intermediate host, the Lymanaea snails - application of molluscicides to decrease the population of Lymnaea snails.

• The opportunity for water source contamination by human and non-human hosts

• Dietary practices that include the consumption of raw, untreated aquatic vegetation.