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# Dracunculus medinensis

- Parasite
- For completeness

A worm caught by drinking water with water fleas. It comes out through a blister on the leg. It is on the verge of eradication.

Updated 2026-11-01

Also called: Guinea worm, dracunculiasis

## Key points

- Caught by drinking water with copepods; prevention is filtering water.
- A leg blister from which the worm emerges about a year later.
- No drug and no vaccine: it is on track to be the first parasitic disease eradicated.
- Infections in dogs are now the main obstacle.

## At a glance

**Type**
Tissue nematode

**Stain**
Rhabditiform larvae seen under the microscope in ulcer fluid

**Size**
The adult female reaches close to a metre in length

## Morphology

- Very long, whitish, thin adult female seen emerging from the ulcer.
- Rhabditiform larvae released when the ulcer touches water.

## Transmission

- Drinking unfiltered water with copepods (water fleas) carrying larvae.
- No person-to-person spread; infected dogs keep the cycle going in some areas.

**Reservoir:** Humans; Infected dogs, cats and baboons

### Isolation precautions

What the care team adds to standard precautions.

- Standard

## Life cycle

- A person drinks water with copepods carrying larvae.
- Gastric juice frees the larvae, which cross the gut wall into the abdominal cavity.
- Males and females mature and mate; the female migrates through the subcutis.
- About a year later she forms a painful blister, nearly always on the leg or foot.
- When the ulcer is put in water, the female releases larvae that copepods swallow.
- In about two weeks the larvae are infective inside the copepod.

## Virulence factors

- Slow emergence of the worm causes a very painful ulcer that becomes secondarily infected.
- Disability lasts weeks and disrupts work and school in rural communities.

## Diseases it causes

- Dracunculiasis: painful leg ulcer with the worm emerging

## Clinical picture

- A burning blister on the lower limb that bursts and lets the worm out over days or weeks.
- Secondary bacterial infection, cellulitis, arthritis and sometimes tetanus.

## Diagnosis

- Clinical: the worm visible in the ulcer is unmistakable and communities recognise it.
- Larvae in ulcer fluid; there is no serological test.

## Treatment

No drug kills the worm and there is no vaccine. It is pulled out little by little by winding it on a stick, with wound care; antibiotics treat secondary infection.

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

## Prevention

- Filtering drinking water (cloth or pipe filters) and access to protected wells.
- Treating stagnant water with the larvicide temephos to kill copepods.
- Keeping people with an emerging worm out of water sources.
- Active surveillance of human and animal cases for certification.

## In Colombia

Absent from Colombia and the Americas. Today it persists only in rural areas of a few African countries (Chad and South Sudan account for recent human cases); it matters as an example of eradication without a vaccine or a drug.

## Memory aid

The little dragon comes out of the water and goes back to the water: it enters with drinking water and shows up in the leg when the leg touches water.

## Test yourself

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

## How does a person become infected with Dracunculus medinensis?

By drinking unfiltered water containing copepods (water fleas) infected with larvae.

## What is the treatment of dracunculiasis?

No drug kills the worm: it is slowly wound out and the wound is cared for, with antibiotics if it becomes infected.

## Which measures sustain Guinea worm eradication?

Filtering water, treating it with temephos, keeping patients out of water, and surveillance of human and animal cases.

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## Related

- [Onchocerca volvulus](https://durgical.com/en/microbiology/onchocerca-volvulus/)
- [Loa loa](https://durgical.com/en/microbiology/loa-loa/)

## 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.

[← Back to the group: Other parasites of interest](https://durgical.com/en/microbiology/groups/other-parasites-of-interest/)

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

Sources: [CDC - DPDx - Dracunculiasis](https://www.cdc.gov/dpdx/dracunculiasis/index.html) (CDC, 2024); [Dracunculiasis (Guinea-worm disease)](https://www.who.int/news-room/fact-sheets/detail/dracunculiasis-(guinea-worm-disease)) (WHO, 2025).

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Representative model, for educational purposes only.

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