Dracunculus medinensis

Source: Wikipedia, the free encyclopedia.
This article is about the human parasite D. medinensis. For the disease, see Dracunculiasis.

"Guinea worm" redirects here. For more parasites also called Guinea worms, see Dracunculus (nematode).

Guinea worm
Photomicrograph of larvae
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Nematoda
Class: Secernentea
Order: Camallanida
Family: Dracunculidae
Genus: Dracunculus
Species:
D. medinensis
Binomial name
Dracunculus medinensis
Synonyms

Gordius medinensis Linnaeus, 1758

Dracunculus medinensis (Guinea worm, dragon worm, fiery serpent[1]) is a nematode that causes dracunculiasis, also known as guinea worm disease.[2] The disease is caused by the female[3] which, at around 80 centimetres (31 inches) in length,[4] is among the longest nematodes infecting humans.[5] In contrast, the longest recorded male Guinea worm is only 4 cm (1+1⁄2 in).[4]

Guinea worm is on target to be the second infectious disease of humans to be eradicated, after smallpox. It was formerly endemic to a wide swath of Africa and Eurasia; as of 2023, it remains endemic in 5 countries: Chad, Mali, South Sudan, Angola and Ethiopia,[6] with most cases in Chad. Guinea worm spread to Angola c. 2018, and it is now considered endemic there. Infection of domestic dogs is a serious complication in Chad.

The common name "guinea worm" is derived from the

Western Africa
.

History

Dracunculus medinensis ("little dragon from Medina") was described in Egypt as early as the 15th century BCE and possibly was the "fiery serpent" afflicting the Israelites described in the Bible.[7]

In the mid-19th century, the nematode

intermediate hosts.[8]

Life cycle

General lifecycle of D. medinensis in humans

D. medinensis L1

Cyclops. Within the copepod, the D. medinensis larvae develop to an infective L3 stage within 14 days.[9] When the infected copepod is ingested by a mammalian host drinking unfiltered water, the copepod is then dissolved by stomach acid and dies and the D. medinensis larvae are released and migrate through the wall of the mammalian intestine, and enter the abdominal cavity and retro-peritoneal space, where they mature into adults. After maturing and mating within the host, the males die and females (length 70–120 cm) migrate in subcutaneous tissue towards the skin's surface. Around a year after the infection, the female causes the formation of a blister on the skin's surface, generally on the lower extremities, though occasionally on the hand or scrotum. When the blister ruptures, the female slowly emerges over the course of several days or weeks.[9] This causes extreme pain and irritation to the host. During those few days to hours before the worm exits the skin, the person may develop a fever, pain, or swelling in that area. When the host — in an attempt to alleviate the excruciating burning pain — submerges the affected body part in water, the female releases thousands of larvae into the water. From here, the larvae infect copepods, continuing the life cycle.[9] After the worm exits the skin the wound caused by the emerging worm often develops a secondary bacterial infection. Permanent damage can occur if the infection goes untreated around a joint. Most cases occur in areas without access to health care facilities.[10]

Animal reservoirs

In 2020, Guinea worm was found in 1507 domestic dogs in Chad, 15 in Ethiopia, and eight in Mali, as well as in 61 domestic cats in Chad and three in Ethiopia. Small numbers have also been found in wildcats and baboons.[11] These findings are a potential problem for the eradication program.

Epidemiology

D. medinensis is most commonly found in the

Cyclops (copepods), that dwell in stationary bodies of water such as ponds, large, open wells (with stairs), or rain-filled cisterns.[12] The infection occurs most during times of drought or the "dry-season" in humid climates, or during or just after the rain season in the "semiarid, wet-and-dry-climates".[12] This is due to the lower surface water of the stationary bodies of water, which are prime for the growth of the infected copepods, and main source of water for many.[12]

Pathology

D. medinensis causes

calcified in or along the joint or finds its way into the central nervous tissue.[13] Aseptic abscesses and cystic swelling can also occur when worms rupture before emerging, causing an acute inflammatory response from the host's immune system.[13]

Treatment

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.[14] 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.[15] Once secure, topical antibiotics are applied to the affected region, to help prevent secondary infections due to bacteria, which is then wrapped in gauze to protect the wound. The same steps are repeated each day until the whole worm has been removed from the lesion.[14]

Eradication program

Main article: Eradication of dracunculiasis
Guinea worm cases by year[16]
Year Reported cases Countries
1986 estimated 3,500,000 21[17]
1989 892,055 15[18]
1992 374,202 15[18]
1995 129,852 19[18]
2000 75,223 16[18]
2001 63,717 16[18]
2002 54,638 14[18]
2003 32,193 13[18]
2004 16,026 13[18]
2005 10,674 12[18]
2006 25,217 [a] 10 [18]
2007 9,585 9[18]
2008 4,619 7[18]
2009 3,190 5
2010 1,797 4[20] (6[21])
2011 1,060 4[22]
2012 542 4[23]
2013 148 5[24]
2014 126 4[25]
2015 22 4[26]
2016 25 3[17]
2017 30 2[27]
2018 28 3[28]
2019 54 [b] 4[29]
2020 27 6[30]
2021 15 4[31]
2022 13 4[32]

In the 1980s, the Carter Center initiated a program to eradicate the guinea worm.[33] The campaign began in 1980 at the U.S. Centers for Disease Control and Prevention. In 1984, the CDC was designated by the World Health Organization as the "Collaborating Center for Research, Training, and Eradication of D. medinensis". More than twenty countries were affected by Guinea worms in 1986. That year, WHO started the eradication program with the Carter Center leading the effort.[34] The program included education of people in affected areas that the disease was caused by larvae in drinking water, isolation and support for affected people, 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.[33] The International Commission for the Certification of Dracunculus Eradication has certified 198 countries, territories, and other WHO represented areas. As of January 2015, eight countries were yet to be certified as Guinea worm-free: Angola, the Democratic Republic of the Congo, Kenya, Sudan, Chad, Ethiopia, Mali, and South Sudan; of these, only in Chad, Ethiopia, Mali, and South Sudan does D. medinensis remain endemic countries.[34]

See also

Explanatory notes

  1. ^ Increase in reported cases resulted from improved reporting in southern Sudan following the peace agreement in 2005.[19]
  2. ^ Increase over 2018 due to increased reporting, due to cash rewards in Chad for reporting cases.[29]

References

  1. ISBN 978-981-16-7203-3
    .
  2. PMID 18258273
    .
  3. PMID 17767406
    .
  4. ^
    ISBN 978-0-07-128458-5
    .
  5. PMID 17591014
    .
  6. ISBN 978-92-4-007333-3
    .
  7. ^ "Dracunculiasis: Historical background". who.int. World Health Organization. Archived from the original on 18 October 2014. Retrieved 27 April 2017.
  8. ISBN 978-0-85199-786-5
    – via Google Books.
  9. ^ a b c "Dracunculiasis: About Guinea-Worm Disease". who.int. World Health Organization. Archived from the original on 1 November 2006. Retrieved 20 December 2015.
  10. ^ "General information – frequently asked questions (FAQs)". Guinea Worm Disease. U.S. Centers for Disease Control and Prevention (CDC). 17 September 2020. Retrieved 24 October 2020.
  11. The Carter Center
    . 26 January 2021.
  12. ^
    PMID 161522
    .
  13. ^
    OCLC 812614125
    .
  14. ^
    Centers for Disease Control
    (CDC). 16 March 2018. Retrieved 22 July 2018.
  15. ISBN 978-1-61-592224-6
    – via Google Books.
  16. The Carter Center
    .
  17. ^ a b Martin, Jeff (11 January 2017). "Carter: Guinea worm disease reported in 3 countries in 2016". Associated Press. Archived from the original on 12 January 2017. Retrieved 11 January 2017.
  18. ^ a b c d e f g h i j k l
    Dracunculiasis Epidemiological Data (1989-2008) (PDF). who.int (Report). World Health Organization. Retrieved 14 September 2009.
  19. PMID 17703170
    . Retrieved 16 March 2011.
  20. The Carter Center. Archived from the original
    on 6 September 2011. Retrieved 22 July 2018.
  21. ^ "Monthly report on dracunculiasis cases, January–December 2010" (PDF). Weekly Epidemiological Record. 86 (10). WHO: 92. 4 March 2011. Retrieved 4 March 2011.
  22. The Carter Center
    (cartercenter.org).
  23. The Carter Center
    (cartercenter.org).
  24. The Carter Center
    (cartercenter.org).
  25. The Carter Center
    . 11 January 2015. Retrieved 9 May 2015.
  26. The Carter Center
    (cartercenter.org).
  27. The Carter Center. 19 January 2018. Archived
    from the original on 20 January 2018. Retrieved 22 July 2018.
  28. The Carter Center
    . 6 May 2019.
  29. ^
    The Carter Center
    . January 2020.
  30. The Carter Center
    . 2021.
  31. The Carter Center
    (cartercenter.org).
  32. ^ "Guinea worm disease reaches all-time low: Only 13* human cases reported in 2022". The Carter Center. 24 January 2023. Retrieved 29 January 2023.
  33. ^ a b "This species is close to extinction, and that's a good thing". Time. World Science Festival. 23 January 2015.
  34. ^ a b "Eradication program". Parasites – Guinea worm. U.S. Centers for Disease Control and Prevention. 2 May 2017. Retrieved 22 July 2018.

External links

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