Dracunculus medinensis
Encyclopedia
Dracunculus medinensis is a nematode
that causes dracunculiasis
.
Dracunculiasis, also known as Guinea worm disease, is caused by the large female nematode, Dracunculus medinensis, which is among the longest nematodes infecting humans. The adult female is primarily larger than the adult male. The longest adult female recorded was 800 millimetres (31.5 in), while the adult male was only 40 mm (1.6 in). Mature female worms migrate along subcutaneous tissues to reach the skin below the knee, forming a painful ulcerating blister. They can also emerge from other parts of the body like the head, torso, upper extremities, buttocks, and genitalia.
s (small crustacean
s) that have been infected with D. medinensis larvae. After ingestion, the copepods die and release the stage 3 larvae, which then penetrate the host's stomach
, intestinal wall, and enter into the abdominal cavity
and retroperitoneal space. After maturing, adult male worms die while the females migrate in the subcutaneous tissue
s towards the surface of the skin. After about a year of infection, the female worm forms a blister on the skin, generally on the distal lower extremity (foot), which breaks open. The patient then seeks to relieve the local discomfort by placing their foot in water, but when the lesion comes into contact with water, the female worm emerges and releases her stage 1 larvae. The larvae are then ingested by a copepod, and after two weeks (and two molts) the stage 3 larvae becomes infectious. Ingestion of the copepods is the last stage that completes the cycle.
(the African eye worm), Mansonella streptocerca
, and Onchocerca volvulus
(river blindness).
hosts, that is, each generation of worms has to pass through a human.
and paralysis
in the spinal cord
.
Control efforts have been highly successful via preventing contamination of drinking water and killing copepods with insecticides. Water sources can be treated with an approved larvicide that kills copepods, such as Abate, without posing a great risk to humans or other wildlife.
The traditional technique which involves winding the worm out on a stick has been a treatment used successfully for centuries. This treatment is memorialized in one of the modern symbols of Medicine, the Rod of Asclepius
. An alternative method is done by surgically removing the worm. The surgical procedure is only successful if the entire worm is near the surface of the skin. Drugs such as metronidazole may relieve symptoms, but activity against the worm remains questionable.
(WHO) asked the Centers for Disease Control and Prevention
(CDC) to spearhead the effort of its eradication, an effort that was further supported by the Carter Center
. Major progress has been made: in 1985 still 3.5 million cases were reported annually, by 2008 that number had dropped to 5,000.
persuaded President Zia al-Haq of Pakistan to accept the proposal of the eradication program and by 1993, Pakistan was free of the disease. Key to the effort was, according to Carter, the work of "village volunteers" who educated people about the need to filter drinking water. Other countries followed, and by 2004 the worm was eradicated in Asia.
is winning the battle against the Guinea worm disease, recording a zero infection rate in the month of November 2009. In the year 2008, 501 new cases were recorded, against 3,357 cases in 2007, representing about an 85% reduction. A number of interventions in the previous two years had been pursued, including monitoring dams and other sources of drinking water in endemic communities to ensure that infected people did not contaminate the water sources. Additionally, filters and other water treatment equipment were provided at both water pumping sites and homes to treat water before drinking. This is all due to the efforts of the National Guinea Worm Eradication Program, funded by the World Health Organization
(WHO), UNICEF, the Japanese International Cooperation Agency (JICA), and the European Union
(EU).
("little dragon from Medina") derives from its one-time high incidence in the city of Medina
, and its common name, Guinea worm, is due to a similar past high incidence along the Guinea coast of West Africa
; both of these locations are now free of Guinea worm. In the 18th century, a Swedish naturalist, Carl Linnaeus, identified D. medinensis in merchants who traded along the Gulf of Guinea
(West African Coast), hence the name Guinea worm.
Nematode
The nematodes or roundworms are the most diverse phylum of pseudocoelomates, and one of the most diverse of all animals. Nematode species are very difficult to distinguish; over 28,000 have been described, of which over 16,000 are parasitic. It has been estimated that the total number of nematode...
that causes dracunculiasis
Dracunculiasis
Dracunculiasis , also called guinea worm disease , is a parasitic infection caused by Dracunculus medinensis, a long and very thin nematode . The infection begins when a person drinks stagnant water contaminated with copepods infested by the larvae of the guinea worm...
.
Dracunculiasis, also known as Guinea worm disease, is caused by the large female nematode, Dracunculus medinensis, which is among the longest nematodes infecting humans. The adult female is primarily larger than the adult male. The longest adult female recorded was 800 millimetres (31.5 in), while the adult male was only 40 mm (1.6 in). Mature female worms migrate along subcutaneous tissues to reach the skin below the knee, forming a painful ulcerating blister. They can also emerge from other parts of the body like the head, torso, upper extremities, buttocks, and genitalia.
Life cycle
Humans become infected by drinking unfiltered water containing copepodCopepod
Copepods are a group of small crustaceans found in the sea and nearly every freshwater habitat. Some species are planktonic , some are benthic , and some continental species may live in limno-terrestrial habitats and other wet terrestrial places, such as swamps, under leaf fall in wet forests,...
s (small crustacean
Crustacean
Crustaceans form a very large group of arthropods, usually treated as a subphylum, which includes such familiar animals as crabs, lobsters, crayfish, shrimp, krill and barnacles. The 50,000 described species range in size from Stygotantulus stocki at , to the Japanese spider crab with a leg span...
s) that have been infected with D. medinensis larvae. After ingestion, the copepods die and release the stage 3 larvae, which then penetrate the host's stomach
Stomach
The stomach is a muscular, hollow, dilated part of the alimentary canal which functions as an important organ of the digestive tract in some animals, including vertebrates, echinoderms, insects , and molluscs. It is involved in the second phase of digestion, following mastication .The stomach is...
, intestinal wall, and enter into the abdominal cavity
Abdominal cavity
The abdominal cavity is the body cavity of the human body that holds the bulk of the viscera. It is located below the thoracic cavity, and above the pelvic cavity. Its dome-shaped roof is the thoracic diaphragm , and its oblique floor is the pelvic inlet...
and retroperitoneal space. After maturing, adult male worms die while the females migrate in the subcutaneous tissue
Subcutaneous tissue
The hypodermis, also called the hypoderm, subcutaneous tissue, or superficial fascia is the lowermost layer of the integumentary system in vertebrates. Types of cells that are found in the hypodermis are fibroblasts, adipose cells, and macrophages...
s towards the surface of the skin. After about a year of infection, the female worm forms a blister on the skin, generally on the distal lower extremity (foot), which breaks open. The patient then seeks to relieve the local discomfort by placing their foot in water, but when the lesion comes into contact with water, the female worm emerges and releases her stage 1 larvae. The larvae are then ingested by a copepod, and after two weeks (and two molts) the stage 3 larvae becomes infectious. Ingestion of the copepods is the last stage that completes the cycle.
Disease
Dracunculus medinensis is one of four filarial nematodes that cause subcutaneous filariasis in humans. The other three filarial nematodes are Loa loaLoa loa
Loa loa is the filarial nematode species that causes Loa loa filariasis. It is commonly known as the "eye worm". Its geographic distribution includes Africa and India....
(the African eye worm), Mansonella streptocerca
Mansonella streptocerca
Mansonella streptocerca, , is the scientific name of a human parasitic roundworm causing the disease of streptocerciasis...
, and Onchocerca volvulus
Onchocerca volvulus
Onchocerca volvulus is a nematode that causes onchocerciasis or "river blindness" mostly in Africa. Long-term corneal inflammation, or keratitis, leads to thickening of the corneal stroma which ultimately leads to blindness. Humans are the only definitive host for O. volvulus. The intermediate host...
(river blindness).
Epidemiology
To become infected, a person must drink water from stagnant sources (e.g., ponds) contaminated with copepods that contain immature forms of the parasite (juveniles), which have been previously released from the skin of a definitive host. The infection can also be acquired by eating a fish paratenic host, but this is rare. The parasite is known to be found in Africa and India. There are no reservoirReservoir
A reservoir , artificial lake or dam is used to store water.Reservoirs may be created in river valleys by the construction of a dam or may be built by excavation in the ground or by conventional construction techniques such as brickwork or cast concrete.The term reservoir may also be used to...
hosts, that is, each generation of worms has to pass through a human.
Pathology
Female worms elicit allergic reactions during blister formation as they migrate to the skin, causing an intense burning pain. Such allergic reactions produce rashes, nausea, diarrhea, dizziness, and localized edema. Upon rupture of the blister, allergic reactions subside but skin ulcers form, through which the worm can protrude. Only when the worm is removed is healing complete. Death of adult worms in joints can lead to arthritisArthritis
Arthritis is a form of joint disorder that involves inflammation of one or more joints....
and paralysis
Paralysis
Paralysis is loss of muscle function for one or more muscles. Paralysis can be accompanied by a loss of feeling in the affected area if there is sensory damage as well as motor. A study conducted by the Christopher & Dana Reeve Foundation, suggests that about 1 in 50 people have been diagnosed...
in the spinal cord
Spinal cord
The spinal cord is a long, thin, tubular bundle of nervous tissue and support cells that extends from the brain . The brain and spinal cord together make up the central nervous system...
.
Diagnosis
Diagnosis of dracunculiasis is made by direct observation of the worms emerging from the lesions appearing on the legs of infected individuals and by microscopic examinations of the larvae.Prevention and control
Guinea worm disease is transmitted via drinking contaminated water. A fine-mesh cloth filter such as nylon, can be used to remove the diseased worm-containing crustacean, or water can be boiled to make it safe to drink.Control efforts have been highly successful via preventing contamination of drinking water and killing copepods with insecticides. Water sources can be treated with an approved larvicide that kills copepods, such as Abate, without posing a great risk to humans or other wildlife.
Treatment
Rod of Asclepius
The rod of Asclepius , also known as the asklepian, is an ancient symbol associated with astrology, the Greek god Asclepius, and with medicine and healing. It consists of a serpent entwined around a staff. The name of the symbol derives from its early and widespread association with Asclepius, the...
. An alternative method is done by surgically removing the worm. The surgical procedure is only successful if the entire worm is near the surface of the skin. Drugs such as metronidazole may relieve symptoms, but activity against the worm remains questionable.
Eradication
Dracunculiasis, a disease unique to humans, can be eradicated by providing safe water supply which prevents D. medinensis from completing its life cycle. In 1984 the World Health OrganizationWorld Health Organization
The World Health Organization is a specialized agency of the United Nations that acts as a coordinating authority on international public health. Established on 7 April 1948, with headquarters in Geneva, Switzerland, the agency inherited the mandate and resources of its predecessor, the Health...
(WHO) asked the Centers for Disease Control and Prevention
Centers for Disease Control and Prevention
The Centers for Disease Control and Prevention are a United States federal agency under the Department of Health and Human Services headquartered in Druid Hills, unincorporated DeKalb County, Georgia, in Greater Atlanta...
(CDC) to spearhead the effort of its eradication, an effort that was further supported by the Carter Center
Carter Center
The Carter Center is a nongovernmental, not-for-profit organization founded in 1982 by former U.S. President Jimmy Carter and his wife Rosalynn Carter. In partnership with Emory University, The Carter Center works to advance human rights and alleviate human suffering...
. Major progress has been made: in 1985 still 3.5 million cases were reported annually, by 2008 that number had dropped to 5,000.
Pakistan
In the 1980s U.S. President Jimmy CarterJimmy Carter
James Earl "Jimmy" Carter, Jr. is an American politician who served as the 39th President of the United States and was the recipient of the 2002 Nobel Peace Prize, the only U.S. President to have received the Prize after leaving office...
persuaded President Zia al-Haq of Pakistan to accept the proposal of the eradication program and by 1993, Pakistan was free of the disease. Key to the effort was, according to Carter, the work of "village volunteers" who educated people about the need to filter drinking water. Other countries followed, and by 2004 the worm was eradicated in Asia.
Sudan
Eradication in Sudan had proven to be difficult, and although Carter had brought about a six-month armistice in 1995 - the "Guinea worm ceasefire" - to allow volunteers enter the region in safety, endemic sections remain.Ghana
GhanaGhana
Ghana , officially the Republic of Ghana, is a country located in West Africa. It is bordered by Côte d'Ivoire to the west, Burkina Faso to the north, Togo to the east, and the Gulf of Guinea to the south...
is winning the battle against the Guinea worm disease, recording a zero infection rate in the month of November 2009. In the year 2008, 501 new cases were recorded, against 3,357 cases in 2007, representing about an 85% reduction. A number of interventions in the previous two years had been pursued, including monitoring dams and other sources of drinking water in endemic communities to ensure that infected people did not contaminate the water sources. Additionally, filters and other water treatment equipment were provided at both water pumping sites and homes to treat water before drinking. This is all due to the efforts of the National Guinea Worm Eradication Program, funded by the World Health Organization
World Health Organization
The World Health Organization is a specialized agency of the United Nations that acts as a coordinating authority on international public health. Established on 7 April 1948, with headquarters in Geneva, Switzerland, the agency inherited the mandate and resources of its predecessor, the Health...
(WHO), UNICEF, the Japanese International Cooperation Agency (JICA), and the European Union
European Union
The European Union is an economic and political union of 27 independent member states which are located primarily in Europe. The EU traces its origins from the European Coal and Steel Community and the European Economic Community , formed by six countries in 1958...
(EU).
Etymology
Dracunculiasis once plagued a wide band of tropical countries in Africa and Asia. Its Latin name, Dracunculus medinensis,("little dragon from Medina") derives from its one-time high incidence in the city of Medina
Medina
Medina , or ; also transliterated as Madinah, or madinat al-nabi "the city of the prophet") is a city in the Hejaz region of western Saudi Arabia, and serves as the capital of the Al Madinah Province. It is the second holiest city in Islam, and the burial place of the Islamic Prophet Muhammad, and...
, and its common name, Guinea worm, is due to a similar past high incidence along the Guinea coast of West Africa
West Africa
West Africa or Western Africa is the westernmost region of the African continent. Geopolitically, the UN definition of Western Africa includes the following 16 countries and an area of approximately 5 million square km:-Flags of West Africa:...
; both of these locations are now free of Guinea worm. In the 18th century, a Swedish naturalist, Carl Linnaeus, identified D. medinensis in merchants who traded along the Gulf of Guinea
Gulf of Guinea
The Gulf of Guinea is the northeasternmost part of the tropical Atlantic Ocean between Cape Lopez in Gabon, north and west to Cape Palmas in Liberia. The intersection of the Equator and Prime Meridian is in the gulf....
(West African Coast), hence the name Guinea worm.