Dracunculiasis

 

By Holly Nesmith

 

 

Common Name:  Guinea worm

 

Genus Species/Etiologic Agent: Dracunculiasis medinensis

 

Means of Transmission:  D. medinensis is transmitted through a cyclical process.  Humans drink water that contains small crustaceans, which contain Guinea worm larvae.  The larvae are released from the crustaceans upon death; they then enter the abdominal cavity where they mature and mate.  The male Guinea worm dies as the females make there way toward the epidermis forming a blister.  Water relieves the burning sensation caused by the Guinea worm.  When placed in water the female D. medinensis releases her eggs into water sources.  Once the larvae are ingested by crustaceans the cycle begins again.[1]  These crustaceans are located in still ponds. 

 

Identification:  The identification and taxonomy of nematodes is not set in stone.  It continually changes and can make classification and identification difficult.   The Guinea worm is in Phylum Nematoda.  “These helminths are the roundworms, having elongated cylindrical unsegmented bodies, covered in a tough inert cuticle, which may, depending on the species, have striations, lateral spines, terminal expansions or other modifications.” It is part of the superfamily Dracunculoidea.  The species in this phylum share some general characteristics in their life cycle.  They go through various stages of larvae and are transferred to a host for maturation.  There are usually both male and female sexes.  The Guinea worm is distinctive because it must be transmitted in fresh water.[2]

 

Current outbreaks:  There is no local incidence rate for the Guinea worm.  It has been largely eradicated and is now endemic in only twelve countries – all of which are located in sub-Saharan Africa.[3]  (See map of countries below) The majority of cases are in Sudan.  There the Guinea worm has been difficult to eradicate due to civil war.  However, overall the number of cases has been reduced from 3.5 million cases in 1986 to 33,000 in 2003.[4]

 

History:  The Guinea worm is a well documented and historic disease.  It has even been found in Egyptian tombs.  Many scholars believe it is the fiery serpent referred to in the Old Testament.  It traveled from Mesopotamia as most diseases did along the trade routes and spread across Europe and Africa. There is detailed documentation of the signs and symptoms of the disease even in the 9th century. During the 18th century, Carlus Linnaeus, suggested the infection resulted from worms and named it the Guinea worm due to the prevalence of the disease in the Gulf of Guinea.  In 1870, Alesej Pavlovich Fedchenko documented the lifecycle of the worm, which was confirmed by Robert Thomas Leiper (1905) and Dyneshvar Atmaran Turkhud (1913). [5]

 

Signs and Symptoms:  Most infected persons do not demonstrate signs or symptoms until a year following infection – this is usually only noticed once the worm starts to emerge.  Inflammation of the area, (redness, swelling, pain, tenderness) skin lesions, and fever are the most common symptoms, which are accompanied by secondary bacterial infections.  This period is accompanied by intense many times crippling pain.  Many times infection can lead to permanent disabling of the person. D. medinensis most often surfaces from the upper and lower extremities, usually emerging from the hands and feet.[6]

 

 

Virulence:  The Guinea worm can be considered extremely virulent.  Once ingested the larvae adheres to the intestine and moves through the wall into the peritoneal cavity.  The first line of defense cells has proven ineffective against the worm, although they are present.[7]

 

Treatment:  The Guinea worm emerges from the skin in a slow and painful process.  It is slowly wrapped around a small stick to prevent it from breaking.  Wet compresses can be applied to the infected area or medication can be administered to reduce pain.  Antibiotics are also an important administered. Although they have no effect on the worm itself, they help to prevent infection of the lesion.  These procedures can reduce the amount of time the Guinea worm takes to emerge. “No anti-helminthic medication is effective against the disease, and there is no vaccine.”[8]

 

Eradication/Prevention: Eradication of the Guinea worm is very possible.  Since the arthropod vector is known, by controlling it, the life cycle of the worm can be stopped.  The most common means of prevention is filtering water before drinking. Eradication efforts began in earnest in 1980 through the CDC.  Over the years it worked and convinced the WHO, Carter Center, UNICEF, and World Bank to push the eradication of the disease.  Once they were onboard, they worked to establish eradication programs in the countries with endemic infection.  Since inception they have greatly reduced the incidence rate.  Although hoped to have been eradicated by 1995, the Guinea worm has remained stubbornly resistance in a few countries.  One of the problems with eradication has been the regulation of animals that can also suffer from this parasite. 7 

 

 

Video to Watch

http://www.cartercenter.org/health/guinea_worm/index.html

 



 



[1] ANON, Dracunculiasis, 4/14/05, http://www.dpd.cdc.gov/dpdx/HTML/Dracunculiasis.htm, 11/30/06

[2] Stewart, T., Detailed Taxonomy of the Parasitic Helminths, 10/05/1998, http://www.path.cam.ac.uk/~schisto/Taxonomy/Old.Taxonomy.html ,12/05/06

[3]ANON, Dracunculiasis Eradication Program, 7/3/2005 http://www.who.int/countries/eth/areas/cds/dracunculiasis/en/ ,11/30/06

[4] ANON, To The Source: Guinea Worm Eradication in Africa, 07/27/2004, http://www.cartercenter.org/news/documents/doc1788.html, 12/05/06

[5] ANON, Dracunculiasis, no date indicated, http://www.who.int/ctd/dracun/dates.htm, 12/05/06

[7] Cairncross, S., Muller, R., Zagaria, N., 04/00/2002. http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=118073&tools=bot, 12/05/06

[8] Greenway, Chris.  Dracunculiasis, 02/17/04, http://www.cmaj.ca/cgi/content/full/170/4/495, 12/05/06