Chapter 326. Dracunculiasis

Dracunculiasis (dracontiasis, guinea worm disease) is caused by infection of subcutaneous and connective tissues with the guinea worm Dracunculus medinensis. Humans are the only known reservoir. Once a scourge affecting thousands of people around the world, the range of this organism has been greatly reduced as a result of a global eradication program spearheaded by the Carter Center’s Global 2000 program. After an estimated 3.5 million cases in 1986, 25,217 cases were reported in 2006.1Over 180 countries have now been certified as free of guinea worm by the World Health Organization. Currently, the Carter Center and the Centers for Disease Control and Prevention (CDC) estimate that the incidence of guinea worm infection fell by 95% between 1986 and 1996 such that it is now estimated that there are fewer than 10,000 cases, which are limited to five African countries—Sudan, Ghana, Nigeria, Niger, and Mali. Sudan alone accounts for more than two thirds of the total cases reported worldwide. Virtually all cases occur in rural, isolated areas. The economic impact of infection is significant, with adults losing about 100 days of work and children missing 25% of school when symptomatic.2,3

When an individual drinks water contaminated with freshwater copepods (plankton) of the genus Cyclops, which contain mature guinea worm larvae, infective larvae are set free, penetrate the intestinal wall, and usually migrate to the retroperitoneal tissues (eFig. 326.1).4 Sixty to 90 days after infection, mating occurs and the males subsequently die. Females then require about 8 to 12 months to mature. The gravid female worm, averaging 1 m in length by 1 to 2 mm in diameter (eFig. 326.2), usually migrates from the deep connective tissues to emerge in the superficial subcutaneous tissues of the distal portions of the arms and legs. More than 90% of worms emerge from the lower extremities, mainly below the knees. Following development of an indurated papule, a painful skin blister forms near the anterior portion of the worm, and infected individuals frequently immerse the affected limb into water to relieve the pain. The affected area ulcerates and when the ulcer is immersed in water, large numbers of motile larvae are discharged into the water through a ruptured prolapsed loop of the parasite’s uterus (Fig. 326-1). If larvae are expelled into a body of water used for drinking, such as a pond, they may be ingested by copepods and the cycle repeats.5

Because of the 1-year incubation period between infection and onset of symptoms, human disease rates reflect risk factors from the previous year. In Africa, infection usually occurs during the hot, dry season when water sources are limited. Infection begins in childhood, and individuals are reinfected repeatedly throughout life. Infection is uncommon before the age of 3 years, because young children and infants seldom drink infected pond or well water.

Worms in the deep tissues usually cause no side effects. Nevertheless, migration to the skin may take many weeks or months and be accompanied by mild or severe hypersensitivity reactions such as urticaria, pruritus, erythema, and, on occasion, dyspnea and a shocklike state.6 Skin ulcers are most common on the ankle or between the metatarsal bones, but they have been described on almost every site. Usually 1 to 3 worms emerge simultaneously, but up to 14 have been documented from a single person in one season. A mild-to-moderate eosinophilia usually accompanies the infection. Secondary infection of the ulcer and worm tract may provoke abscesses and septic arthritis, producing chronic deformities, contractures, and muscle atrophy. Tetanus is a common complication in inadequately immunized persons.

Dracunculiasis can be diagnosed only when the skin ulcer appears or if the outline of the adult worm can be seen beneath the skin; immunologic tests are not reliable. Surgical removal of the worm frequently is advocated. The time-honored method of gradually rolling the worm onto a stick, a few centimeters a day, is still used today; this ancient procedure is also the inspiration for the caduceus, the symbol of medicine. However, it is important to do this when the worm first appears and to take suitable precautions to prevent sepsis. Severe inflammation and necrosis usually follow if the worm is torn during removal, and the traditional slow removal process takes an average of 89 days. Measures suggested to facilitate manual removal include killing the worm by local infiltration with acriflavine or mercuric bichloride and emptying the worm of eggs by applying a continuous water drip onto gauze-covered ulcers.

The role of chemotherapy in dracunculiasis is limited. Three antiparasitic drugs—niridazole, metronidazole, and thiabendazole—have been advocated to reduce inflammation, thereby reducing the time required for extraction. (Niridazole is not available in the United States.) Response to these drugs varies from no effect, with continued appearance of new worms, to death of the organism in the tissues associated with increased inflammation, anaphylaxis, and arthritides. No antiparasitic drug can reliably be expected to produce beneficial effects. In fact, mebendazole is associated with aberrant migration of worms. Topical antibiotics can reduce the risk of superinfection.

Establishing safe drinking water is the principal intervention needed to disrupt transmission. This may be achieved by chemical treatment with temephos (Abate), which is safe for consumption at concentrations used for water treatment, or by filtering out zooplankton using cloth or nylon filters. Together with health education and active surveillance, the global eradication program has markedly reduced the prevalence of this disease.