[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [Microbiology](https://durgical.com/en/microbiology/) › Trematodes (flukes)

[Microbiology](https://durgical.com/en/microbiology/) · [Parasites](https://durgical.com/en/microbiology/#d-parasite)

# Trematodes (flukes)

- Parasites

Leaf-shaped flatworms that need a snail to complete their cycle. They arrive with raw plants, fish or crabs, or through the skin in fresh water.

Updated 2026-11-01

## What they are

Trematodes are unsegmented flatworms with suckers. All pass through a freshwater snail, where they multiply. Foodborne flukes are acquired by eating metacercariae on aquatic plants, fish or crustaceans; Schistosoma enters through the skin.

## What they share

- Flat, leaf-shaped body with oral and ventral suckers.
- Freshwater snail as the first intermediate host.
- Operculated eggs (except Schistosoma, which has a spine).
- Hermaphroditic, except Schistosoma, which has separate sexes.

## Key points

- A snail is obligatory in every cycle.
- Praziquantel for nearly all; Fasciola needs triclabendazole.
- Schistosoma: through the skin, no operculum, has a spine.
- Clonorchis and Opisthorchis viverrini: cholangiocarcinoma.
- Paragonimus mimics tuberculosis.

## Microorganisms in this group

- [**Fasciola hepatica** 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. Exam priority: medium](https://durgical.com/en/microbiology/fasciola-hepatica/)
- [**Schistosoma mansoni / S. haematobium / S. japonicum** A worm that enters through the skin when bathing in fresh water with infected snails. Its eggs damage the liver, bowel or bladder. Exam priority: medium](https://durgical.com/en/microbiology/schistosoma-mansoni-s-haematobium-s-japonicum/)
- [**Paragonimus spp.** A flatworm that comes with raw freshwater crabs or crayfish and settles in the lung. It causes bloody cough and is mistaken for tuberculosis. For completeness](https://durgical.com/en/microbiology/paragonimus-spp/)
- [**Clonorchis sinensis / Opisthorchis spp.** Liver flukes from raw freshwater fish in Asia. They live for years in the bile ducts and raise the risk of bile duct cancer. For completeness](https://durgical.com/en/microbiology/clonorchis-sinensis-opisthorchis-spp/)

## Test yourself

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

## Which intermediate host do all trematodes share?

A freshwater snail.

## Which trematode does not respond to praziquantel?

Fasciola hepatica, which is treated with triclabendazole.

## Which trematode enters the body through the skin?

Schistosoma, whose cercariae penetrate the skin in fresh water.

[Add to my cards (3)](https://durgical.app/estudiar/?add=/en/microbiology/groups/trematodes/)

[← All of microbiology](https://durgical.com/en/microbiology/)

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

Sources: [Foodborne trematode infections](https://www.who.int/news-room/fact-sheets/detail/foodborne-trematode-infections) (WHO, 2021); [Schistosomiasis](https://www.who.int/news-room/fact-sheets/detail/schistosomiasis) (WHO, 2026); [CDC - DPDx - Fascioliasis](https://www.cdc.gov/dpdx/fascioliasis/index.html) (CDC, 2019).

## **Spotted a mistake?** We are always improving for the community. Tell us what is wrong and our team will review it. Report a mistake

Representative model, for educational purposes only.

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