Fasciola hepatica !

Parasite
Exam priority: medium

A flatworm of livestock that reaches humans through raw watercress or other water plants. It tunnels through the liver and lives in the bile ducts.

Updated 2026-11-01

Also called: sheep liver fluke, fascioliasis

At a glance

Shape: Flat leaf with a cephalic cone and oral and ventral suckers
Family: Fasciolidae
Type: Hepatic trematode (liver fluke), hermaphroditic
Size: Adult 2–3 cm

Morphology

Large egg (130–150 × 60–90 µm), ellipsoidal, operculated and unembryonated.
Very similar to the Fasciolopsis buski egg.
Flat, leaf-shaped adult in the bile ducts.

Transmission

Eating raw watercress or other aquatic plants carrying metacercariae.
Drinking water with floating metacercariae.
Not spread between people.

Reservoir: Cattle and sheep (main); Other herbivores; Lymnaeid snails as intermediate host

Isolation precautions

What the care team adds to standard precautions.

Standard

Life cycle

Unembryonated eggs leave in livestock or human faeces and mature in fresh water.
The miracidium infects a lymnaeid snail, where it multiplies (sporocyst, redia, cercaria).
Cercariae leave and encyst as metacercariae on aquatic plants such as watercress.
When the plants are eaten, the metacercaria excysts in the duodenum and crosses the wall to the peritoneum.
It pierces the liver capsule, migrates through the parenchyma and reaches the bile ducts.
In the bile ducts it matures and starts laying eggs after 3–4 months.

Virulence factors

Acute phase: migration through the parenchyma destroys tissue and leaves haemorrhagic tracks.
Chronic phase: adults inflame and block the bile ducts.
Promotes stones, cholangitis, pancreatitis and fibrosis.
Ectopic migration to skin, lung or other organs.

Diseases it causes

Fascioliasis, acute hepatic and chronic biliary
Acute cholangitis from biliary obstruction Acute cholangitis →

Clinical picture

Acute phase: fever, right upper quadrant pain, tender hepatomegaly, urticaria and marked eosinophilia.
Chronic phase: intermittent biliary colic, jaundice, anaemia.
May be silent for years.

Diagnosis

Serology (EIA confirmed by immunoblot): positive in the acute phase, before eggs appear.
Eggs in stool, duodenal aspirate or bile in the chronic phase.
CT with hypodense tracks in the liver; ERCP may show the flukes.
Pseudofascioliasis: eggs in stool after eating infected liver; repeat the test after avoiding liver.

Treatment

Triclabendazole is the drug of choice; praziquantel is not effective against Fasciola. Biliary obstruction may need ERCP.

Drug class only; doses and regimens are set by the clinician from the current guideline.

Prevention

Do not eat raw watercress or aquatic plants from areas with livestock.
Cook aquatic plants and use safe water.
Treat livestock and control snails.

Test yourself

Think of the answer, then tap the question to see it.

Which food typically transmits Fasciola hepatica?

Raw watercress or other aquatic plants carrying metacercariae.

Why is serology useful in acute fascioliasis?

Antibodies appear at 2–4 weeks, before the fluke starts laying eggs.

What is the drug of choice for fascioliasis?

Triclabendazole; praziquantel is not effective against Fasciola.

What is pseudofascioliasis?

Finding Fasciola eggs in stool after eating infected liver, without real infection.

Add to my cards (4)

Acute cholangitis

← Back to the group: Trematodes (flukes)

Educational content on microorganisms; not a treatment guide and no substitute for a health professional's advice. No doses are given.

Sources: CDC - DPDx - Fascioliasis (CDC, 2019); Foodborne trematode infections (WHO, 2021); Parasitosis humanas (Corporación para Investigaciones Biológicas (CIB), 2019).

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Representative model, for educational purposes only.