Microbiology · Other parasites of interest
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
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.
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.
Related
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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 (CDC, 2024); Dracunculiasis (Guinea-worm disease) (WHO, 2025).
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Representative model, for educational purposes only.