Guinea worm, the little dragon
The scientific Latin name of this exotic parasite is Dracunculus medinensis, meaning little dragon. The common synonyms are: Medina worm, Guinea worm, serpent worm and dragon worm. Infection with this parasite causes Drunculiasiis, a disease of considerabe socio-economic significance in the countries affected.
This nematode has been found in Egyptian mummies and was known as a parasite of humans about 1530 B.C. It is thought that the fiery serpent on the end of Moses's stick, which plagued the Israellites by the Red Sea in the Biblical story was really Dracunculus. The disease they caused was recognized and named Drancunculiasis by Galen. 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.
Most medical associations around the world, including the World Health Organization, use the traditional symbol of medicine, the staff of Asclepius with a single serpent encircling a staff. The single serpent staff also appears on a Sumerian vase of c. 2000 B.C. representing the healing god Ningishita, the prototype of the Greek Asklepios, whereas Caduceus is the staff of Hermes and contains coiled winged serpents on a staff. There is some confusion between the Caduceus and the staff of Asclepius, the true symbol of medicine. Many people use the word Caduceus to mean both of these emblems. The serpents are believed to represent the Guinea worm.
In ancient times worms infection was common. Dracunculus medinensis crawled around the victim's body, just under the skin. Physicians treated this infection by cutting a slit in the patient's skin, just in front of the worm's path. As the worm crawled out of the cut, the physician patiently twisted it around a stick until the entire animal had been removed. It is believed that physicians advertised their services by displaying a sign with the worm on a stick.
Distribution and Epidemiology
The Guinea-worm is a parasite of the dog, horse, cow, wolf, leopard, monkey, and baboon and also commonly infects man.
Guinea worm infections occur primarily in areas with low rainfall or in areas where rainfall is seasonal. The pattern of infection is related to the availability of water. Most infections take place near the end of the dry season when water is found in small pools and stepwells. At this time the intermediate host copepods are present in larger numbers.
In the 1950s, Guinea worm was estimated to infect about 50 million people in tropical regions with one or more annual dry seasons, in mainly Africa and Asia. Due to concentrated efforts by the international community and the endemic countries, the number of cases of guinea-worm disease was reduced to about 32 000 by 2003. Guinea-worm disease is now prevalent in only 12 countries, all in Africa (Sudan, Nigeria, Ghana, Burkina Faso, Niger, Togo and Côte d'Ivoire, Mauritania, Benin, Chad, Ethiopia and Uganda).
Little dragon and the Cyclops
Dracunculus medinensis is a nematode (roundworm). Although often classified with the filarian worms, it is not a true filaria. The Guinea worm is one of the largest nematodes known. The female adult worms are about a meter in length, but have a diameter of only 2 mm, resembling a cooked spaghetti. The inconspicuous males are only about 2 to 3 cm long.
The infection is caused by drinking water contaminated with the intermediate hosts, the water fleas Copepods, belonging to various species of the genus Cyclops, infected with larvae. Cyclops are tiny (0.5-2 mm) crustaecians of the family Cyclopediae, just visible to the naked eye in water and recognizable by their jerky swimming.
Pregnant Guinea worm females stick their head out through the skin (90% move to the feet and legs) of infected persons, who, when they enter sources of drinking water, allow the worm to release larvae into the water.
A pustule develops on the skin at the site where the worm will emerge. This blister causes a very painful burning sensation, and ruptures within 24 to 72 hours, exposing the head of the worm. A loop of the uterus prolapses through the body wall.
Tormented by the burning sensation, infected persons often seek relief by immersing the affected limb in water. The pregnant adult female takes this opportunity to release a milky white liquid containing hundreds of thousands of Guinea worm larvae into the water. Over the next several days, the female worm liberates more larvae whenever it comes in contact with water.
These larvae are eaten by the water fleas, in which they develop into infective form in 2 to 3 weeks.
Once the fleas are in the stomach, they, but not the larvae, are digested by the acid gastric juice. The larvae pass into the gut, penetrate the wall of the small intestine and start their wandering as adults through the muscles of the body.
During the next 10–14 months, the female dragon worm
copulates with a male guinea worm, who, poor fellow, dies and is absorbed into the larger female. When it reaches the destination under the skin, the gravid uterus is filled with hundred of thousands of embryos. The intestine becomes squashed and nonfunctional as a result of the pressure of the uterus. The vicious circle
starts anew when the worm infests the drinking water with its progeny.
Symptoms and signs
For about a year after infection, the maturing worms cause no symptoms until they are ready to discharge their larvae. Before the worm emerges through the skin (usually of the lower limb, although any part of the body can be affected) the site is swollen, reddish, painful and tender. Generalized symptoms like fever, nausea vomiting and diarrhea may appear. When the skin is in water, the blister ruptures. Usually only one worm is involved, but in endemic areas there may be more on account of repeated infection. Secondary bacterial infection of the ulcer is common. Particularly serious is the involvement of joints, leading to arthritis. Tetanus is also a serious risk. The symptomatic phase of Dracunculiasis can debilitate a patient for months.
Diagnosis is made from the local blister, worm or larvae. The outline of the worm under the skin may be revealed by reflected light. The pre-emergent worm can be felt under the skin. The sight of the head of the little dragon peeping through the skin is diagnostic. It may be animated to discharge the larvae into water, where they can be seen under the microscope. Calcified dead worms may be found on X-ray examination.
What to do?
Treatment includes the extraction of the adult Guinea worm as in ancient days. 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. The process of removing the worm usually takes weeks or months. If the worm breaks, the individual will experience a painful and serious reaction that may include anaphylaxis.
Metronidazole and Mebendazole are effective in killing the worm. Surgical intervention is through multiple surgical incisions under local anaesthesia.
Avoiding the little dragon
Thanks to a concerted effort by various international agencies over the last few years this parasitic disease may be the first ever to be eradicated. In 1991, the World Health Assembly adopted a resolution to eradicate the disease and started the Dracunculiasis Eradication Programme, which focuses on interruption of transmission of the disease; surveillance of new cases and certification of eradication.
Specific interventions include: health education, case containment, community-based surveillance systems, provision of safe water, including use of filtering devices and chemical treatment of water sources.
Because Drancunculiasis 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. You are advised to
Drink water only 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.
A simple, cheap and very effective way to remove the water fleas is to filter drinking water using a cloth filter, or preferably synthetic gauze filter.
Additionally, unsafe sources of drinking water can be treated with an approved larvicide such as Temephos or Abate, which can kill water fleas.
Boiling the drinking water will kill the Cyclops containing the larvae as well as other vermin.
Communities should be provided with new safe sources of drinking water, or have existing dysfunctional ones repaired.
The way to hell is paved with good intentions
Of course, all these lofty goals suffer setbacks from natural and man made catastrophes. About two-thirds of the cases of Guinea worm disease reported in 2003 were from Sudan, where the continuing civil war is hampering efforts to eradicate the disease. The new war by proxy being fanned in Somalia by some warriors of/on terror is certain to rejuvenate these little, and bigger dragons of pestilence.
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www.iht.com The New York Times By Donald G. McNeil Jr. The New York Times. WEDNESDAY, MAY 31, 2006
Saastri SC et al. Abate, its value as Cycopicide. Jounal of tropical medicine and hygiene, 1978,81:156-158