What Is Worm?
Dracunculiasis, more commonly known as Guinea worm disease (GWD), is an infection caused by the parasite Dracunculus medinensis. The parasite is alternately known in English as "Guinea worm", "Medina worm", and finally "fiery serpent" which reflects the Latin root word Dracunculus meaning "little dragon".
The female Dracunculus worm emerges through the skin of its human host one to two years after infection. Often, persons with emergent worms enter sources of drinking water and unwittingly allow the worm to release larvae into the water. These larvae are ingested by microscopic fresh-water arthropods known as copepods ("water fleas", especially of the genus Cyclops). Inside the copepods, the larvae develop into the infective stage in 10–14 days. In turn, humans may then become infected by drinking water containing infected copepods.
Once inside the body, the stomach acid digests the water flea, but not the guinea worm larvae sheltered inside. These larvae find their way to the small intestine, and then pass into the body cavity. During the next 10–14 months, the female copulates with a male guinea worm. The small male (1.2–2.9 centimeters, 0.5-1.1 inches long) dies and is absorbed into the larger female. The female develops into its full length of 60–100 centimeters (2–3 feet) long and a narrow width similar to that of a cooked spaghetti noodle. Having mated, the adult female is packed with thousands of tiny larvae. The worm migrates to the area of the body from which it will emerge, which, in more than 90% of all cases, is on one of the lower limbs.
A blister develops on the skin at the site where the worm will emerge. This blister causes a very painful burning sensation, and, within 24 to 72 hours of its appearance, will rupture, exposing one end of the emergent worm. To relieve the burning sensation, infected persons often immerse the affected limb in water. When the blister, which shortly becomes an ulcer or open sore, is submerged in water, the adult female releases a milky white liquid, containing hundreds of thousands of guinea worm larvae, into the water. Over the next several days, the female worm is capable of releasing more larvae whenever it comes in contact with water. These larvae contaminate the water supply and are eaten by copepods, thereby repeating the lifecycle of the disease, as described above.
The most common practice to treat dracunculiasis involves wrapping the worm around a stick. This treatment has been employed for millennia and may have inspired the Rod of Asclepius which historically has symbolized the medical profession. As the adult worm first begins to emerge from the patient's skin, it is wrapped or wound around a stick, then further wound by a few centimeters per day. Considering a full-grown worm can measure up to a meter in length, this slow process can take many days or even weeks, but it is required to avoid breakage and leaving behind a portion of the worm. Breaking the worm will not cause the death of the individual; however, having a portion of the dead worm remain within the host's body increases the risk of infection, and can trigger immune responses resulting in pain and swelling. In many countries, a broken worm is immediately removed surgically. The worm also can be excised surgically from the very beginning, where such facilities are available.
Metronidazole or thiabendazole (in adults) is usually adjunctive to stick therapy and somewhat facilitates the extraction process. However, one study found that antihelminthic therapy was associated with aberrant migration of worms, resulting in infection in areas other than the lower extremity. Therefore, such medications should be used with caution.
If history or examination findings lead to suspicion of dracunculiasis, consultation is warranted with an infectious disease specialist for involvement in management and follow-up care. This also allows for initiation of epidemiologic protocol if the patient presents in a non-endemic country.
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