Dracunculus medinensis
| Dracunculus medinensis | |
|---|---|
| Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Nematoda |
| Class: | Secernentea |
| Order: | Camallanidae |
| Superfamily: | Dracunculoidea |
| Family: | Dracunculidae |
| Genus: | Dracunculus |
| Species: | D. medinensis |
| Binomial name | |
| Dracunculus medinensis |
|
Dracunculus medinensis is a nematode that causes Dracunculiasis.[1] Dracunculiasis, also known as Guinea Worm disease, is caused by the large female nematode, Dracunculus medinensis,[2] which is the longest nematode infecting humans.[3] The adult female is primarily larger than the adult male. The longest adult female recorded was 800 mm in length, while the adult male was only 40 mm.[4] Mature female worms migrate along subcutaneous tissues to reach the skin below the knee, forming a painful ulcerating blister.[5] They can also emerge from other parts of the body like the head, torso, upper extremities, buttocks, and genitalia.[6]
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Life Cycle
Humans become infected by drinking unfiltered water containing copepods (small crustaceans) that have been infected with D. medinensis larva. After ingestion, the copepods die and release the larvae, which then penetrates the host's stomach, intestinal wall, and enters into the abdominal cavity and retroperitoneal space. After maturing, adult male worms die while the females migrate in the subcutaneous tissues 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 larvae. The larvae are then ingested by a copepod, and after two weeks (and two molts) the larvae becomes infectious. Ingestion of the copepods is the last stage that completes the cycle.[7]
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),[8] 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 reservoir hosts.[9]
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 arthritis and paralysis in the spinal cord.[10]
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.[11]
Prevention
Guinea worm disease is transmitted via drinking contaminated water. Drink only water from uncontaminated sources. Never drink unfiltered water, use a fine-mesh cloth filter such as nylon, to remove the diseased worm containing crustacean. You may also boil the water before consumption.
Control
Control efforts have been highly successful via preventing contamination of drinking water and killing copepods with insecticides.[12] 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. [13]
Treatment
The traditional technique which involves winding the worm out on a stick has been a treatment used successfully for centuries. 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 have been used but their effectiveness remains questionable.[14]
Guinea Worm
Though dracunculiasis also plagues Ghana, Ethiopia, Mali, Niger, Sudan, India, Pakistan, Senegal, Yemen, & many other parts of the world, due to its high incidence along the Guinea coast of West Africa, the name Guinea worm was more commonly used. [15] In the 18th century, a Swedish naturalist, Carlus Linnaeus, identified D. medinensis in merchants who traded along the Gulf of Guinea (West African Coast), hence the name Guinea worm. [16]
The Battle in Ghana
Ghana 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 percent reduction. A number of interventions in the past 2 years have 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 have been 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. The program is funded by the World Health Organisation (WHO), UNICEF, Japanese International Cooperation Agency (JICA), and European Union (EU).
Other
The official symbol of medicine (the staff with a serpent) and the double-serpent caduceus of the military, is actually a depiction of the removal of D. medinensis.[17]
References
- ^ Knopp S, Amegbo IK, Hamm DM, Schulz-Key H, Banla M, Soboslay PT (March 2008). "Antibody and cytokine responses in Dracunculus medinensis patients at distinct states of infection". Trans. R. Soc. Trop. Med. Hyg. 102 (3): 277–83. doi:10.1016/j.trstmh.2007.12.003. PMID 18258273. http://linkinghub.elsevier.com/retrieve/pii/S0035-9203(07)00408-7.
- ^ Bimi L. 2007. Potential vector species of Guinea worm (Dracunculus medinensis) in Northern Ghana. Vector Borne Zoonotic Dis 7(3): 324-9.
- ^ Saleem T. B., and I. Ahmed. 2006. "Serpent" in the breast. J Ayub Med Coll Abbottabad 18(4): 67-8.
- ^ Schmidt G. D., and L S. Roberts. 2009. Foundations of Parasitology, 8th ed. The McGraw-Hill Companies, Inc., New York, New York, 480-84 p.
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- ^ Centers for Disease Control and Prevention. "Dracunculus medinensis." 2009. <http://www.dpd.cdc.gov/dpdx/HTML/Dracunculiasis.htm> (25 November 2009).
- ^ Centers for Disease Control and Prevention (CDC). 2009. Progress toward global eradication of dracunculiasis, January 2008--June 2009. MMWR Morb Mortal Wkly Rep 16;58(40): 1123-5.
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- ^ Harrat Z., and R. Halimi. 2009. [Imported dracunculiasis: four cases confirmed in the south of Algeria]. Bull Soc Pathol Exot 102(2): 119-22.
- ^ 4
- ^ BASF Agricultural Products. "ABATE®." 2006. <http://www.basfpublichealth.com/products/abate.html> (2 December 2009).
- ^ 4
- ^ The Imaging of Tropical Diseases. "Guinea Worm Infection (Dracunculiasis)." 2008. <http://www.isradiology.org/tropical_deseases/tmcr/chapter27/intro.htm> (2 December 2009).
- ^ WikiAnswers. "Why Dracunculus Medinensis infection is called guinea worm disease?" 2009. <http://wiki.answers.com/Q/Why_Dracunculus_Medinensis_infection_is_called_guinea_worm_disease> (2 December 2009).
- ^ 4
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