Dracunculiasis (Guinea Worm Disease): The Parasite, Its Life Cycle and Diagnosis

Dracunculiasis, or Guinea worm disease, is caused by the roundworm (nematode) Dracunculus medinensis.

Life cycle

1. People are infected by drinking unfiltered water containing copepods — tiny crustaceans — that carry the worm's larvae.
2. Once swallowed, the copepods die and release the larvae, which bore through the stomach and intestinal wall into the abdominal cavity and the space behind it.
3. The larvae mature and mate. The males die; the females, 70 to 120 cm long, travel through the tissue under the skin toward the surface.
4. About a year after infection, the female worm raises a blister on the skin, usually low on the leg, which bursts. When the sore touches water — which the patient seeks, to relieve the pain — the worm emerges and releases larvae.
5. A copepod swallows the larvae, which after two weeks and two molts are infective.
6. Someone drinks the copepods, and the cycle begins again.

The Guinea worm life cycle as CDC draws it: people are infected by drinking water with infected copepods, or by eating undercooked fish that harbour the larvae; the female worm emerges from the skin a year later and releases larvae into water, where copepods take them up. CDC.

Where it occurs

An eradication campaign has cut the disease dramatically. It is now found only in rural, isolated areas in a narrow belt of African countries.

What it does

The effects are local but disabling. The worm emerges as a whitish thread, over 1 to 3 weeks, from the middle of a painful ulcer, with inflammation and often a secondary bacterial infection.

Diagnosis

The illness is so distinctive, and so familiar to people where it occurs, that it needs no laboratory confirmation — which would rarely be available there anyway. The fluid the worm discharges can show rhabditiform larvae under the microscope. There is no blood test.

Treatment

CDC's treatment information is on its Guinea worm pages.

Sources

• Centers for Disease Control and Prevention, DPDx — Laboratory Identification of Parasites of Public Health Concern, "Dracunculiasis." https://www.cdc.gov/dpdx/dracunculiasis/index.html
• CDC, Guinea worm, treatment and recovery: https://www.cdc.gov/guinea-worm/about/index.html
• Photographs of the blister and the emerging worm, credited on the page to Global 2000/The Carter Center, are not reproduced here.