Dracunculiasis

Dracunciliasis, more commonly known as Guinea Worm Disease (GWD), is an infection caused by the parasite Dracunculus medinensis (also known as "Guinea worm"). The word Dracunculus comes from the Latin "little dragon".

Life cycle

An adult female Dracunculus worm emerges through the skin of its human host one year 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 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 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 guinea worm 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.

Epidemiology and consequences of infection

Affected communities are located in tropical regions with one or more annual dry seasons. Typically, the infection is acquired from drinking water: ponds, shallow wells, or other stagnant water that infected humans can enter. As of 2005, all known areas of infection were in a band of countries across sub-Saharan Africa, extending from Côte d'Ivoire to Sudan. Concerted efforts are underway to achieve eradication, and are nearing completion with a recent reduction from an estimated 3.5 million cases in 1986 to approximately 11,500 reported cases in 2005, a 99.5 percent reduction.

People in these remote rural communities, who are most affected by GWD, have limited access to medical care. Almost invariably, the skin lesions caused by the worm develop secondary bacterial infections, which exacerbate the pain, and extend the period of incapacitation to weeks or months-causing in some cases disabling complications, such as locked joints and even permanent crippling. Each time a Guinea worm emerges, persons may be unable to work or resume daily activities for months. The worm usually emerges during planting or harvesting season, resulting in economic costs.

Dogs can also be infected and could play a (limited) role in transmission (Dönges, 1988).

Treatment

Infected individuals usually wind the emergent worm around a small stick; however, they dare only pull out a few centimeters of worm each day, lest the worm break. If the worm breaks, the individual will experience a painful and serious reaction that may include anaphylaxis. Without surgical intervention, the process of removing the worm usually takes weeks or months.

No medication is available to end or prevent infection. However, sometimes the worm can be surgically removed before an ulcer forms. Analgesics, such as aspirin or ibuprofen, can help reduce swelling; antibiotic ointment can help prevent bacterial infections.

Affected countries

According to the Carter Center, the incidence of GWD has dropped from an estimated 3.5 million cases worldwide in 1986 to only 16,026 reported cases in 2004.

Dracunculiasis now occurs only in 12 countries in sub-Saharan Africa. Transmission of the disease is most common in very remote rural villages and in areas visited by nomadic groups. In the 2nd century BC, the Greek writer Agatharchides described this affliction as being endemic amongst certain nomads in what is now Sudan and along the Red Sea (fragments preserved in Photius, Bibliotheca Cod. 250.59, 453b; and Plutarch, Quaestiones Convivales 8.9.16).

In 2004 the three most endemic countries—i.e. Ghana, Sudan, and Nigeria—reported 7,275; 7,266; and 495 cases of GWD respectively. Other endemic countries reporting cases of GWD in 2004 were: Benin (3 cases), Burkina Faso (60 cases), Côte d'Ivoire (21 cases), Ethiopia (17 cases), Mali (357 cases), Mauritania (13 cases), Niger (293 cases), and Togo (278 cases). Kenya (7 cases) and Uganda (4 cases) reported incidences imported from Sudan.

GWD-free countries

Asia is now free of the disease. Transmission of GWD no longer occurs in several African countries, including Kenya, Senegal, Cameroon, Chad, and Central African Republic. No locally acquired cases of disease have been reported in these countries in the last year or more. The World Health Organization has certified 168 countries free of transmission of Dracunculiasis, including four formerly endemic countries: Pakistan (in 1996), India (1996), and in Senegal and Yemen (in 2004).

Prevention

Because GWD can only be transmitted via drinking contaminated water, educating people to follow these simple control measures can completely prevent illness and eliminate transmission of the disease:

Drink only water from underground sources free from contamination, such a borehole or hand-dug wells.
Prevent persons with an open Guinea Worm ulcer from entering ponds and wells used for drinking water.
Always filter drinking water, using a cloth filter, to remove the water fleas.
Additionally, unsafe sources of drinking water can be treated with an approved larvicide such as Abate, that kills water fleas, and communities can be provided with new safe sources of drinking water, or have existing dysfunctional ones repaired.

Cultural references

Guinea worm was once endemic to the Middle East. There is speculation that the "fiery serpent" on the end of Moses's stick in the Biblical story was really one of these parasites.

The Rod of Asclepius, a symbol of medicine, is believed to have once represented Dracunculus medinensis or similar parasite wrapped around a stick.

External links

Parasitic diseases | Water-borne diseases | Tropical disease

Medinawurm | Gusano de Guinea | Dracunculiasi

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