Gordius medinensis Linnaeus, 1758
Dracunculus medinensis or Guinea worm is a nematode that causes dracunculiasis, also known as guinea worm disease. The disease is caused by the female which, at up to 800 mm (31 in) in length, is among the longest nematodes infecting humans. In contrast, the longest recorded male Guinea worm is only 40 mm (1.6 in).
The life-cycle for Dracunculus medinensis starts out when a person drinks water that contains copepods that were initially infected by the L1 larval stage of the guinea worm. Once ingested, the copepod dies. After the copepod dies, the L3 stage of the D. medinensis larvae are released and actively migrate through the host's stomach and intestinal wall. The larvae then enter the abdominal cavity where they mature into adult worms and mate. After mating, the males die and the females start migrating through the subcutaneous tissues to the skin surface. The female worm causes the formation of a blister on the skin's surface approximately one year after the initial infection took place. Once the blister ruptures, the female worm slowly starts to emerge from the lesion. These blisters usually are located on the lower extremities. During the slow emerging process, the worm cause a burning sensation. People often will submerge the lesion in water to relieve the burning sensation. Once in contact with water, the female releases numerous L1 larvae that will later be ingested by copepods to start the cycle over again.
The female guinea worm slowly starts to emerge from the host's skin after the blister ruptures. The most common method for removing the worm involves submerging the affected body part in water to help coax the worm out. The site is then cleaned thoroughly. Then, slight pressure is applied to the worm as it is slowly pulled out of the wound. To avoid breaking the worm, pulling should stop when resistance is met. Full extraction of the female guinea worm usually takes several days. After each day's worth of extraction, the exposed portion of the worm is wrapped around a piece of rolled-up gauze or small stick to maintain tension. This method of wrapping the worm around a stick or gauze is speculated to be the source for the Rod of Asclepius, the symbol of medicine. Once secure, topical antibiotics are applied to affected region to help prevent secondary infections due to bacteria and then is wrapped in gauze to protect the wound. The same steps are repeated each day until the whole worm has been successfully removed from the lesion.
In the 1980s a program to eradicate guinea worm was begun, initiated by the Carter Center. The Guinea Worm Eradication campaign began in 1980 at the US Centers for Disease Control and Prevention. In 1984, the CDC was appointed as the World Health Organization Collaborating Center for research, training, and eradication of Dracunculus medinensis. There were 20 countries in 1986 that were affected by guinea worms. That year, WHO started the eradication program and the Carter Center took the lead on the effort. The program included education of people in affected areas that the disease was caused by larvae in drinking water, isolation and support for sufferers, and – crucially – widespread distribution of net filters and pipe filters for drinking water, and education about the importance of using them.
As of 2015 the species has been reported to be near eradication. The International Commission for the Certification of Dracunculus Eradication (ICCDE) has certified 198 countries, territories, and other WHO represented areas. In January 2015, only eight countries remained to be certified as Dracunculus medinensis free. These eight countries include Angola, Democratic Republic of the Congo, Kenya, Sudan, Chad, Ethiopia, Mali, and South Sudan. Of these, Chad, Ethiopia, Mali, and South Sudan are the only remaining endemic countries.
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- "Centers for Disease Control and Prevention". Parasites – Dracunculiasis (also known as Guinea Worm Disease). Retrieved April 27, 2015.
- Satin, Morton (2007). Death in the Pot: The Impact of Food Poisoning on History. Amherst: Prometheus Books. pp. 63–65.
- World Science Festival. "This Species Is Close to Extinction and That's a Good Thing". TIME.
- Donors Commit $240 Million to Fight Neglected Diseases
- How to Slay a Dragon – documentary by Clifford Bestall, broadcast on Al Jazeera English, Spring 2014 (video, 47 min.)