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ESSENTIALS OF DIAGNOSIS

ESSENTIALS OF DIAGNOSIS

  • Tender cutaneous ulcer and worm protruding from the skin of an individual who has ingested untreated water in rural Africa.

GENERAL CONSIDERATIONS

Dracunculiasis is caused by the nematode Dracunculus medinensis, or Guinea worm. It causes chronic cutaneous ulcers with protruding worms in rural Africa. It was a major cause of disability, but recent control efforts have been remarkably successful. Annual incidence has decreased from about 3.5 million cases in the late 1980s to 27 reported cases in 2020; recent cases were from Chad, Ethiopia, South Sudan, Mali, and Angola. Remarkably, the first case ever described in Angola was reported in 2018. Of concern, infection has also been identified in domestic dogs and cats in endemic countries, with dogs likely providing an important disease reservoir, and reported animal cases now outnumber human cases.

Infection occurs after swallowing water containing the infected intermediate host, the crustacean Cyclops (known as copepods or water fleas). In the stomach, larvae escape from the copepods and migrate through the intestinal mucosa to the retroperitoneum, where mating occurs. Females then migrate to subcutaneous tissue, usually of the legs, over about a year (eFigure 35–40). A subcutaneous ulcer then forms (eFigure 35–41). Upon contact with water, the parasite discharges large numbers of larvae, which are ingested by copepods. Adult worms, which can be up to a meter in length, are gradually extruded. Worm death and disintegration in tissue may provoke a severe inflammatory reaction.

eFigure 35–40.

Life cycle of Dracunculus medinensis (Guinea worm). Humans become infected by drinking unfiltered water containing copepods (small crustaceans) that are infected with larvae of D medinensis

eFigure 35–41.

Worm blister caused by the head of a female Guinea worm (Dracunculus medinensis). A: The female Guinea worm induces a painful blister. B: After rupture of the blister, the worm emerges as a whitish filament in the center of a painful ulcer, which is often secondarily infected. (Reproduced with permission from Global 2000/The Carter Center, Atlanta, Georgia.)

CLINICAL FINDINGS

Patients are usually asymptomatic until the time of worm extrusion, when a painful papule develops, with erythema, pruritus, and burning, usually on the lower leg. Multiple lesions may be present. A short-lived systemic reaction, including fever, urticaria, nausea, vomiting, diarrhea, and dyspnea, may develop in some patients. The skin lesion vesiculates over a few days, followed by ulceration. The ulcer is tender, often with a visible worm. The worm is then extruded or absorbed over a few weeks, followed by ulcer healing. Secondary infections, including infectious arthritis and tetanus, are common. The disease causes significant disability; lesions commonly prevent walking ...

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