Dracunculiasis

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Dracunculiasis, more commonly known as Guinea worm disease (GWD) or Medina Worm, is a parasitic infection caused by the nematode, Dracunculus medinensis. The name, dracunculiasis, is derived from the Latin "affliction with little dragons."^[1] The common name "Guinea worm" appeared after Europeans first saw the disease on the Guinea coast of West Africa in the 17th century.^[2] The painful, burning sensation experienced by the infected patient has led to the disease being called “the fiery serpent.” Once prevalent in 20 nations in Asia and Africa, the disease remains endemic in only five countries in Sub-Saharan Africa. It is hoped that Guinea worm disease will be the first parasitic disease to be eradicated and the first disease in history eradicated through behavior change, without the use of vaccines or a cure.^[3] Guinea worm disease is only contracted when a person drinks stagnant water contaminated with the larvae of the Guinea worm. There is no animal or environmental reservoir of D.medinensis. The infection must pass through humans each year.^[3] Dracunculiasis, or Guinea worm disease in humans, results from infection by the nematode Dracunculus medinensis. The mammogram shows a coiled, whorled-type calcification in the subcutaneous tissues; this finding is characteristic of a dead Guinea worm. In 1986, more than 3.5 million cases of dracunculiasis occurred worldwide.[4] Ten years later, the estimated worldwide annual incidence had declined significantly, with only 152,000 new cases annually, mostly occurring in Sudan. As of 2003, the US Centers for Disease Control and Prevention (CDC) reported the annual incidence at <33,000 cases, again mostly originating in the Sudan.[5] This decline has been a result of the Global Dracunculiasis Eradication Campaign. Dracunculiasis now occurs in only 13 countries in Africa, the Middle East, and in South Asia, including Nigeria, Cameroon, Ghana, Sudan, India, and Pakistan. Infected areas in Africa lie in a band between the Sahara and the equator.[3,4,5]

People acquire dracunculiasis by drinking fresh water contaminated with D medinensis larvae. Exposure can also occur from ingestion of fresh fruits or vegetables washed with contaminated water or from bathing or swimming in infected water. Small water fleas present in the water swallow the D medinensis larvae. The worms continue to mature within the flea. Humans contract the infection by ingesting water that is contaminated with these water fleas. Once inside the body, the stomach acid dissolves the water flea but not the Guinea worm. During the next year, the worms mature to adult size; they mate, and the male dies. At the end of that year, the female worms migrate toward the surface of the body, into the subcutaneous tissue. As a worm migrates, a blister develops on the skin above where the worm resides. The female adult worm eventually emerges from the blister, rupturing the skin. When an infected person comes into contact with water, exposed worms release a milky, white liquid containing millions of immature larvae; these larvae contaminate the water supply. There is a definite seasonal variation in exposure to the organism, which correlates with periods of increased exposure to contaminated water.[3]

The majority of cases involve worms appearing on the legs and feet, but the worms may occur anywhere on the body; cases involving the arms, breasts, head, and back have been well-documented. Less commonly, patients with dracunculiasis can present with worms in other locations, such as the lungs, pancreas, testes, spinal cord, or periorbital tissue. A blister typically forms in the epidermis at the site chosen by the female worm to emerge, usually in the lower extremity. Just before blister formation, symptoms similar to an allergic reaction, such as mild respiratory distress with wheezing, urticaria, periorbital edema, and pruritus, may be noted. Affected individuals may also be febrile during this period. As the worm's head continues to emerge, the blister grows in size and becomes erythematous at its edges. The formation of edema around the site causes further pruritus and burning pain. The blister erupts (usually after a few days, although the eruption can occur after as long as 2 weeks), and the worm releases a milky fluid that is teeming with larvae. The swelling and pain will often decrease after the blister erupts. An ulcer forms around the blister site as the adult worm continues to emerge; the definitive diagnosis is often made at this stage, when the head of the worm is identifiable. No other commonly noted physical findings typically develop, although varying degrees of lymphadenopathy may be found at any stage of the illness.

The live Guinea worm cannot be identified radiologically, except in the rare instances when iodinated contrast medium is injected into the body of the worm to delineate its full extent; however, after it dies, the Guinea worm may become calcified from cell secretion or necrotic cellular debris. The female D medinensis worm appears as a long, stringlike, serpiginous calcification. The calcification is frequently segmented and beaded as muscle movements break up the body of the worm.

If the worm is in the breast, the calcifications may be intramammary, in and around the ducts, in the lobules, in the vascular structures, in interlobular connective tissue, or in the fat. They may also be found in the subcutaneous tissue of the skin. They can appear with or without an associated lesion, and their morphologies and distribution can provide clues to their etiology and to their association with benign or malignant processes. The incidence of breast calcification from Guinea worm infection is difficult to assess because dracunculiasis is rare outside of endemic areas. Cases of dracunculiasis are usually rural and not well documented; however, the breast is probably a relatively rare site of presentation.

Dracunculiasis typically has a low mortality rate, although significant morbidity may occur. Death occurring in this setting is not caused by the primary worm infestation but rather from a secondary bacterial infection at the worm's exit site that can lead to sepsis. Secondary infection of the lesions can be severe. The appearance of cellulitis or the formation of an abscess at the worm's exit site requires prompt attention. Morbidity also includes pain at the exit sites, which occurs frequently and can incapacitate patients for long periods of time, especially those patients with multiple worms (typically, individuals experience multiple worm extrusions simultaneously), as well as patients who rely on their ability to stand or walk for their livelihood. Significant loss of productivity with a resultant negative socioeconomic burden on individuals and communities has been documented; for example, farmers with untreated dracunculiasis in Nigeria have been found to miss work for up to 3 months at a time. Another debilitating complication of dracunculiasis is the development of chronic pain and intermittent swelling of the extremities secondary to the calcified encapsulation of the adult worm upon its death. In a small percentage of individuals, permanent scarring or deformity of the lower extremity may occur.

Of related interest, the universal symbols of medicine (ie, the asklepios, the snake wrapped around a rod that is attributed the Greek god of healing and medicine, as well as the similar caduceus) are likely a representation of dracunculiasis and its treatment. To this day, accepted treatment remains the same. The adult Guinea worm is wrapped around a stick a few centimeters a day to coax it from a person's skin. Removal of the entire worm may take days to weeks. Metronidazole or thiabendazole may be used as an adjunct to stick therapy. These medications, however, have not been proven in controlled clinical trials and may be associated with aberrant migration of the worm; consequently, they should be used with caution. The worm may also be removed surgically, if such facilities are available. Diagnosis of dracunculiasis outside of endemic areas requires consultation with an infectious disease specialist and epidemiologic investigation to prevent additional cases.

[edit] Life cycle

The life cycle of Dracunculus medinensis.

Guinea worm disease thrives in some of the world’s poorest areas, particularly those with limited or no access to clean water.^[4] In these areas, stagnant water sources may host microscopic, fresh-water arthropods known as copepods ("water fleas"), which carry the larvae of the Guinea worm.

Inside the copepods, the larvae develop for approximately two weeks.^[2] At this stage, the larvae can cause Guinea worm disease if the infected copepods are not filtered from drinking water.^[2] The male Guinea worm is typically much smaller (1.2–2.9 centimeters, 0.5-1.1 inches long) than the female, which, as an adult, can grow between 2 and 3 feet (0.91 m) long and be as thick as a spaghetti noodle.^[2][4]

Once inside the body, stomach acid digests the water flea, but not the Guinea worm larvae sheltered inside.^[2] These larvae find their way to the body cavity, where the female mates with a male Guinea worm.^[2] This takes place approximately 3 months after infection.^[2] After mating, the male worm dies and is absorbed.^[2]

The female, which now contains larvae, burrows into the deeper connective tissues or adjacent to long bones or joints of the extremities.^[2]

Approximately one year after the infection began, the worm attempts to leave the body by creating a blister in the human host’s skin—usually on a person’s lower extremities like a leg or foot.^[5]

This blister causes a very painful burning sensation as the worm emerges. Within 24 to 72 hours, the blister will rupture, exposing one end of the emergent worm.

To relieve this burning sensation, infected persons often immerse the affected limb in water. Once the blister or open sore is submerged in water, the adult female releases hundreds of thousands of Guinea worm larvae, contaminating the water supply.

During 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. Infected copepods can only live in the water for 2 to 3 weeks if they are not ingested by a person. Infection does not create immunity, so people can repeatedly experience Guinea worm disease throughout their lifetime.^[4]

In drier areas just below the Sahara desert, cases of the disease often emerge during the rainy seasons, which for many agricultural communities is also the planting or harvesting season. Elsewhere, the emerging worms are more prevalent during the dry season, when scarce surface water is most polluted. Guinea worm disease outbreaks can cause serious disruption to local food supplies and school attendance (see Social and economic impact section).^[4]

[edit] Prevention

Sudanese boys using pipe filters to prevent Guinea worm disease.

Guinea worm disease can only be transmitted from drinking contaminated water. Educating people to follow simple control measures can completely prevent illness and eliminate transmission of the disease, leading to the disease’s eradication:

• Drink only water from underground sources free from contamination, such as a borehole or hand-dug wells.
• Prevent persons with an emerging Guinea worm from entering ponds and wells used for drinking water.
• Always filter drinking water, using a fine-mesh cloth filter like nylon, to remove the Guinea worm-containing water fleas.
• Water sources can be treated with an approved larvicide such as Abate, that kills water fleas, without posing a great risk to humans or other wildlife.^[6]
• Communities can be provided with new safe sources of drinking water, or have existing dysfunctional ones repaired.

[edit] Treatment

The ancient symbol of medicine, the staff of Asklepios, is believed to also represent the treatment of Guinea worm still used today.

There is no vaccine or medicine to treat or prevent Guinea worm disease. Once a Guinea worm emerges, a person must wrap the live worm around a piece of gauze or a stick extracting it from the body in a long, painful process that can take up to a month.^[3] This is the same treatment that is noted in the famous ancient Egyptian medical text, the Ebers papyrus from 1550 B.C..^[2] Some people have said that extracting a Guinea worm feels like they are being stabbed or that the afflicted area is on fire.^[7][8]

Although Guinea worm disease, itself, is usually not fatal, the wound where the worm emerges could develop a secondary bacterial infection such as tetanus, which may be life-threatening—a concern in endemic areas where there is typically limited or no access to health care.^[9] Analgesics can be used to help reduce swelling and pain and antibiotic ointments can help prevent secondary infections at the wound site.^[4]

[edit] Endemic areas

In 1986, there were an estimated 3.5 million cases of Guinea worm in 20 endemic nations in Asia and Africa.^[3] Due to prevention and health education efforts, by the end of 2007, there were fewer than 10,000 cases in five nations in Africa: Sudan, Ghana, Nigeria, Niger, and Mali, and as of June 2008, cases had been reduced by more than 50 percent compared to the same period of 2007.^[10][11][12] Guinea worm disease is expected to be the next disease after smallpox to be eradicated.^[7]

[edit] Social and economic impact of Guinea worm disease

The pain caused by the worm’s emergence—which typically occurs during planting and harvesting seasons—prevents many people from working or attending school for as long as 2 to 3 months. In heavily burdened agricultural villages, fewer people are able to tend their fields or livestock, resulting in food shortages and lower earnings.^[13][3] For example, a study in southeastern Nigeria found that rice farmers in a small area lost US$20 million in just one year due to outbreaks of Guinea worm disease.^[3]

[edit] Eradication efforts

[edit] Declaring Guinea worm disease eradicable

The global campaign to eradicate Guinea worm disease began at the U.S. Centers for Disease Control and Prevention (CDC) in 1980. In 1986, former U.S. President Jimmy Carter and his not-for-profit organization, The Carter Center, began leading the global campaign, in conjunction with CDC, UNICEF, and WHO.^[14]

Carter has said a personal visit to a Guinea worm endemic village in 1988 spurred his efforts to eradicate the disease: “Encountering those victims first-hand, particularly the teenagers and small children, propelled me and Rosalynn to step up the Carter Center’s efforts to eradicate Guinea worm disease.”^[15]

President Carter also recruited two African former heads of state to the battle against Guinea worm disease. Then-former head of state of Mali, General Amadou Toumani Toure (since elected President of Mali) has been a strong advocate of Guinea worm eradication in Mali and all other French-speaking African endemic countries since 1992.^[16][17] Since 1999, former Nigerian head of state General (Dr.) Yakubu Gowan has played a similar role in Nigeria, which at the eradication campaign's start had more cases than any other country.^[18]

Since humans are the only host for Guinea worm, the disease can be controlled by identifying all cases and modifying human behavior to prevent it from recurring.^[3] Once all human cases are eliminated, the disease cycle will be broken, resulting in its eradication.^[3]

In 1991, the World Health Assembly (WHA) agreed that Guinea worm disease should be eradicated.^[9] The Carter Center has continued to lead the eradication efforts, primarily through its Guinea Worm Eradication Program.^[19] Other major actors in the eradication of Guinea worm disease include: World Health Organization, U.S. Centers for Disease Control and Prevention, Bill & Melinda Gates Foundation, and UNICEF,^[13][19] but the global coalition now includes dozens of other donors, nongovernmental organizations, and institutions, most especially the ministries of health of the affected countries themselves.

[edit] Barriers to eradication

The eradication of Guinea worm disease has faced several challenges:

• inadequate security in some endemic countries;
• lack of political will from some endemic country leaders;
• the need for change in behavior in the absence of a ‘magic bullet’ treatment like a vaccine or medication; and
• inadequate funding at certain times.^[1]

One of the most significant challenges facing Guinea worm eradication has been the civil war in southern Sudan, which was largely inaccessible to health workers due to violence.^[1][20] To address some of the humanitarian needs in southern Sudan, in 1995, the longest ceasefire in the history of the war was achieved through negotiations by Jimmy Carter.^[1][20] Commonly called the “Guinea worm cease-fire,” both warring parties agreed to halt hostilities for nearly six months to allow public health officials to immunize children and begin Guinea worm eradication programming, among other interventions.^[20]Hopkins, Donald R. & Withers, P. Craig, Jr., "Sudan's war and eradication of dracunculiasis", The Lancet 360: s21-s22 

Public health officials cite the formal end of the war in 2005, as a turning point in Guinea worm eradication because it has allowed health care workers greater access to southern Sudan’s endemic areas.^[13] One remaining area in West Africa outside of Ghana remains challenging to ending Guinea worm: northern Mali, where Tuareg rebels have made some affected areas unsafe for health workers.

[edit] Status of eradication efforts

The World Health Organization is the international body that certifies whether a disease has been eliminated from a country or eradicated from the world. Endemic countries must report to the International Commission for the Certification of Dracunculiasis Eradication and document the absence of indigenous cases of Guinea worm disease for at least 3 consecutive years to be certified as Guinea worm-free by the World Health Organization.^[21]

List of countries that have stopped transmission of Guinea worm or been WHO-certified as having eliminated the disease:^[22]

Stopped Transmission in

• Benin - 2004
• Burkina Faso - 2006
• Chad - 1998
• Cote d'lvoire - 2006
• Ethiopia - 2006
• Kenya - 1994
• Mauritania - 2004
• Togo - 2006
• Uganda - 2003

WHO Certified

• Cameroon - 2007
• Central African Republic - 2007
• India - 2000
• Pakistan - 1996
• Senegal - 2004
• Yemen - 2004

[edit] Guinea worm through history

• The unusually high incidence of dracunculiasis in the city of Medina led to it being included in part of the disease’s scientific name “medinensis.” A similar high incidence along the Guinea coast of West Africa gave the disease its more commonly used name.^[2] Guinea worm is no longer endemic in either location.
• The 2nd century B.C., Greek writer Agatharchides, described this affliction as being endemic amongst certain nomads in what is now Sudan and along the Red Sea.^[2]
• Guinea worm has been found in calcified Egyptian mummies.^[3]
• Many believe certain symbols of medicine—the caduceus and the staff of Asklepios—represent the treatment for Guinea worm disease, as they portray either one or two snakes wrapped around a stick.^[23]
• Guinea worm may be the “fiery serpent” that plagued the Israelites in the Old Testament: “And the Lord sent fiery serpents among the people, and they bit the people; and much people of Israel died.” (Numbers 21:4-9).^[2]
• However the first who described dracunculiasis and its proper treatment was the Bulgarian physician Hristo Stambolski, during his exile in Yemen.^[24] His theory was that the cause was infected water which people were drinking.

[edit] See also

• Infectious disease in the 20th century
• List of infectious diseases
• Tropical disease
• Neglected disease
• Waterborne diseases
• Eradication of infectious disease
• Parasitism
• Smallpox
• Polio

[edit] Notes

[edit] External links

• The Carter Center Guinea Worm Disease Eradication Program
• Center for Disease Control information on Dracunculiasis
• Tropical Medicine Central Resource: “Guinea Worm Infection (Dracunculiasis)”
• World Health Organization on Dracunculiasis