[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [Microbiology](https://durgical.com/en/microbiology/) › [Trematodes (flukes)](https://durgical.com/en/microbiology/groups/trematodes/) › Intestinal flukes (Fasciolopsis, Heterophyes, Metagonimus, Echinostoma)

# Intestinal flukes (Fasciolopsis, Heterophyes, Metagonimus, Echinostoma)

- Parasite
- For completeness

Flatworms that live in the small intestine after eating raw water plants, fish or snails. Mostly Asian; usually mild, heavy loads cause diarrhoea.

Updated Nov 13, 2026

Also called: Fasciolopsis buski, giant intestinal fluke, Heterophyes heterophyes, Metagonimus yokogawai, Echinostoma spp.

## Quick facts

**Type**
Parasite · [Trematodes (flukes)](https://durgical.com/en/microbiology/groups/trematodes/)

**Gram / shape**
Leaf-shaped flukes

**Spread**
Fasciolopsis · Heterophyes and Metagonimus

**Causes**
Fasciolopsiasis · Heterophyiasis and metagonimiasis

**Treatment**
Praziquantel is the drug of choice for intestinal flukes

On this page

- The basics Key points
- At a glance
- Morphology
- Transmission
- Life cycle
- In Colombia
- Memory aid
- What the colours mean

- Clinical Virulence factors
- Diseases it causes
- Clinical picture
- Diagnosis

- Treatment Treatment
- Prevention

- Study Test yourself

- Connections Connections

## Key points

- Fasciolopsis buski: largest human intestinal fluke; raw water plants; pigs.
- Its egg is almost identical to the Fasciola egg.
- Heterophyes/Metagonimus: smallest flukes; raw fish; eggs like Clonorchis.
- Echinostoma: spiny collar; raw snails and clams.
- Treatment: praziquantel.

## At a glance

**Shape**
Leaf-shaped flukes; operculated eggs

**Family**
Fasciolidae (Fasciolopsis); Heterophyidae (Heterophyes, Metagonimus); Echinostomatidae (Echinostoma)

**Type**
Food-borne digenean trematodes of the small intestine

**Size**
Fasciolopsis up to several centimetres (the largest human intestinal fluke); heterophyids 1–2.5 mm (the smallest)

## Morphology

- Fasciolopsis egg: large, operculated, 130–150 µm, almost identical to the Fasciola hepatica egg.
- Heterophyes and Metagonimus eggs: tiny, embryonated, resembling Clonorchis and Opisthorchis eggs.
- Echinostoma: a collar of spines around the oral sucker; large eggs that resemble Fasciola eggs.
- Eggs alone often cannot name the genus; the adult fluke is needed.

## Transmission

- Fasciolopsis: eating raw water plants (water chestnut, water caltrop) with metacercariae.
- Heterophyes and Metagonimus: eating raw, undercooked or salted freshwater or brackish fish.
- Echinostoma: eating raw snails, clams, fish or tadpoles.

**Reservoir:** Fasciolopsis: pigs and humans; Heterophyids: fish-eating mammals and birds; Echinostoma: birds and mammals; snails and other aquatic animals as intermediate hosts

### Isolation precautions

What the care team adds to standard precautions.

- Standard

## Life cycle

- Eggs leave in the stool and reach fresh water.
- A miracidium (or the egg itself, in heterophyids) infects a specific snail.
- In the snail the fluke multiplies through sporocyst and redia stages and releases cercariae.
- Cercariae encyst as metacercariae on water plants (Fasciolopsis) or in fish, snails or tadpoles.
- A person eats the raw plant or animal; metacercariae excyst and adults attach to the small intestine.

## Virulence factors

- Attachment of the flukes causes local inflammation and ulcers of the mucosa.
- Heavy Fasciolopsis loads cause malabsorption, oedema and ascites (protein loss) or obstruction.
- Heterophyid eggs can enter the circulation and lodge in the heart or brain.

## Diseases it causes

- Fasciolopsiasis: diarrhoea, abdominal pain, oedema and ascites in heavy infections
- Heterophyiasis and metagonimiasis: diarrhoea and colicky pain; rarely egg emboli to the heart or brain
- Echinostomiasis: abdominal pain, diarrhoea and eosinophilia

## Clinical picture

- Most infections are light and asymptomatic.
- Heavy infections: diarrhoea, epigastric pain, anorexia, weight loss.
- Fasciolopsis: facial and generalised oedema, ascites, intestinal obstruction.
- Eosinophilia is common.

## Diagnosis

- Eggs in stool (or vomitus for Fasciolopsis) on direct smear or concentration.
- Measure eggs: large ones point to Fasciolopsis, Fasciola or Echinostoma; tiny ones to heterophyids or Clonorchis.
- Species identification needs adult flukes passed after treatment.

## Treatment

Praziquantel is the drug of choice for intestinal flukes; triclabendazole, used for Fasciola, is not the standard for these.

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

In Pharmacology:

- [Praziquantel](https://durgical.com/en/pharmacology/praziquantel/)

## Prevention

- Cook water plants, fish, snails and clams; peel or dip water plants in boiling water.
- Do not use untreated human or pig faeces to fertilise fish ponds or water crops.
- Sanitation; a One Health approach combining food safety and veterinary measures.

## In Colombia

These intestinal flukes are mainly Asian (Fasciolopsis in Asia and the Indian subcontinent; heterophyids in Egypt, the Middle East and the Far East). In Colombia, Fasciola hepatica is the food-borne fluke of practical relevance.

## Memory aid

Plant, fish, snail: the giant comes on the water chestnut, the dwarfs come with the fish, and the spiny collar comes with the snail; praziquantel clears all three.

## Test yourself

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

## Which is the largest intestinal fluke of humans and how is it acquired?

Fasciolopsis buski, by eating raw water plants carrying metacercariae.

## Which liver fluke egg is almost identical to the Fasciolopsis egg?

The Fasciola hepatica egg.

## Which food transmits Heterophyes and Metagonimus?

Raw, undercooked or salted freshwater or brackish fish.

## What drug is used to treat intestinal fluke infections?

Praziquantel.

[Add to my cards (4)](https://durgical.app/estudiar/?add=/en/microbiology/intestinal-flukes/)

## What the colours mean

**Gram-positive**
Thick peptidoglycan wall: stains purple.

**Gram-negative**
Thin wall with an outer membrane: stains pink.

**Acid-fast**
Lipid-rich wall (mycobacteria): Ziehl–Neelsen stain.

## Connections

## Related 4

- [Fasciola hepatica](https://durgical.com/en/microbiology/fasciola-hepatica/)
- [Clonorchis sinensis / Opisthorchis spp.](https://durgical.com/en/microbiology/clonorchis-sinensis-opisthorchis-spp/)
- [Paragonimus spp.](https://durgical.com/en/microbiology/paragonimus-spp/)
- [Schistosoma mansoni / S. haematobium / S. japonicum](https://durgical.com/en/microbiology/schistosoma-mansoni-s-haematobium-s-japonicum/)

[← Back to the group: Trematodes (flukes)](https://durgical.com/en/microbiology/groups/trematodes/)

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

Sources: [CDC - DPDx - Fasciolopsiasis](https://www.cdc.gov/dpdx/fasciolopsiasis/index.html) (CDC, 2024); [CDC - DPDx - Heterophyiasis](https://www.cdc.gov/dpdx/heterophyiasis/index.html) (CDC, 2018); [CDC - DPDx - Metagonimiasis](https://www.cdc.gov/dpdx/metagonimiasis/index.html) (CDC, 2017); [CDC - DPDx - Echinostomiasis](https://www.cdc.gov/dpdx/echinostomiasis/index.html) (CDC, 2019).

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Representative model, for educational purposes only.

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Source: https://durgical.com/en/microbiology/intestinal-flukes/
License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/microbiology/intestinal-flukes/