View source for Biology:Dracunculus medinensis

{{Short description|Species of parasitic worm}}
{{italic title}}
{{Speciesbox
| name = Guinea worm
| image = Dracunculus medinensis larvae.jpg
| image_caption = Photomicrograph of larvae
| genus = Dracunculus (nematode)
| species = medinensis
| authority = ([[Biography:Carl Linnaeus|Linnaeus]], [[Biology:10th edition of Systema Naturae|1758]])
| synonyms = ''Gordius medinensis'' <small>[[Biography:Carl Linnaeus|Linnaeus]], [[Biology:10th edition of Systema Naturae|1758]]</small>
}}

'''''Dracunculus medinensis''''' ('''Guinea worm''', '''dragon worm''', '''fiery serpent'''<ref name="Eradicate fiery serpent zoonosis">{{Cite book|year=2022|pages=427–436|last=Chaudhury|first=Abhijit|title=Textbook of Parasitic Zoonoses |doi=10.1007/978-981-16-7204-0_41|chapter=Dracunculiasis|series=Microbial Zoonoses |isbn=978-981-16-7203-3 }}</ref>) is a [[Biology:Nematode|nematode]] that causes [[Medicine:Dracunculiasis|dracunculiasis]], also known as guinea worm disease.<ref name=pmid18258273>{{cite journal |author1=Knopp, Stefanie |author2=Amegbo, Ignace K. |author3=Hamm, David M. |author4=Schulz-Key, Hartwig |author5=Banla, Meba |author6=Soboslay, Peter T. |date=March 2008 |title=Antibody and cytokine responses in ''Dracunculus medinensis'' patients at distinct states of infection |journal=Transactions of the Royal Society of Tropical Medicine and Hygiene |volume=102 |issue=3 |pages=277–283 |pmid=18258273 |doi=10.1016/j.trstmh.2007.12.003 }}</ref> The disease is caused by the female<ref>{{cite journal |author=Bimi, Langbong |year=2007 |title=Potential vector species of Guinea worm (''Dracunculus medinensis'') in northern Ghana |journal=Vector-Borne and Zoonotic Diseases |volume=7 |issue=3 |pages=324–329 |doi=10.1089/vbz.2006.0622 |pmid=17767406}}</ref> which, at around {{convert|80|cm|in|abbr=off}} in length,<ref name="Schmidt-Roberts-2009">{{cite book |author1=Schmidt |first=Gerald D. |title=Foundations of Parasitology |author2=Roberts |first2=Larry S. |publisher=McGraw-Hill |year=2009 |isbn=978-0-07-128458-5 |editor1=Roberts |editor-first=Larry S. |edition=8th |pages=480–484 |editor2=Janovy |editor-first2=John Jr.}}</ref> is among the longest nematodes infecting humans.<ref name=Saleem>{{cite journal |author1=bin&nbsp;Saleem, Talha |author2=Ahmed, Irfan |year=2006 |title="Serpent" in the breast |journal=Journal of Ayub Medical College Abbottabad |volume=18 |issue=4 |pages=67–68 |url=http://www.ayubmed.edu.pk/JAMC/PAST/18-4/014%20Tallah%20bin%20Saleem%20(CR).pdf |pmid=17591014}}</ref> In contrast, the longest recorded male Guinea worm is only {{convert|4|cm|in|frac=2|abbr=on}}.<ref name=Schmidt-Roberts-2009/>

Guinea worm is on target to be the second infectious disease of humans to be eradicated, after [[Medicine:Smallpox|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,<ref name="Eradicate human dracunculiasis">{{Cite book |author=Control of Neglected Tropical Diseases team |title=Criteria for the certification of dracunculiasis eradication 2023 update |publisher=[[Organization:World Health Organization|World Health Organization]] |year=2023 |isbn=978-92-4-007333-3 |editor-last=[[Organization:World Health Organization|World Health Organization]] |pages=9,26}} </ref> with most cases in Chad. Guinea worm spread to Angola {{circa|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 [[Place:Guinea (region)|Guinea region]] of Western Africa.

==History==
''Dracunculus medinensis'' ("little dragon from Medina") was described in Egypt as early as the {{nobr|15th century BCE}} and possibly was the "[[Unsolved:Fiery flying serpent|fiery serpent]]" afflicting the Israelites described in the Bible.<ref>{{cite web |title=Dracunculiasis: Historical background |publisher=[[Organization:World Health Organization|World Health Organization]] |website=who.int |access-date=27 April 2017 |url=https://www.who.int/dracunculiasis/background/en/  |archive-url=https://web.archive.org/web/20141018070914/http://www.who.int/dracunculiasis/background/en/ |archive-date=October 18, 2014}}</ref>

In the mid-19th century, the nematode ''[[Biology:Camallanus lacustris|Camallanus lacustris]]'', which infects freshwater fish, was discovered to develop in copepods. This led Russian naturalist Alexei Pavlovich Fedchenko to discover in 1870 that ''D.&nbsp;medinensis'' is similarly transmitted via copepod intermediate hosts.<ref name=Anderson2000>{{cite book |author=Anderson, Roy C. |date=8 February 2000 |title=Nematode Parasites of Vertebrates: Their development and transmission |publisher=CABI |isbn=978-0-85199-786-5 |page=1 |url=https://books.google.com/books?id=lEERbfsvP1EC |via=Google Books}}</ref>

==Life cycle==
[[File:Drac life cycle.png|right|thumb|General lifecycle of ''D.&nbsp;medinensis'' in humans]]

''D.&nbsp;medinensis'' L1 larvae are found in fresh water, where they are ingested by [[Biology:Copepod|copepod]]s (small crustaceans) of the genus [[Biology:Cyclops (genus)|''Cyclops'']]. Within the copepod, the ''D.&nbsp;medinensis'' larvae develop to an infective L3 stage within 14&nbsp;days.<ref name=WHOAbout>{{cite web |title=Dracunculiasis: About Guinea-Worm Disease |website=who.int |publisher=[[Organization:World Health Organization|World Health Organization]] |url=https://www.who.int/dracunculiasis/disease/en/   |access-date=20 December 2015 |archive-url=https://web.archive.org/web/20061101203805/http://www.who.int/dracunculiasis/disease/en/ |archive-date=November 1, 2006}}</ref> 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.&nbsp;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&nbsp;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.<ref name=WHOAbout/> 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.<ref name=WHOAbout/> 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 [[Medicine:Septic arthritis|around a joint]]. Most cases occur in areas without access to health care facilities.<ref>{{cite web |title=General information – frequently asked questions (FAQs) |department=Guinea Worm Disease |publisher=U.S. Centers for Disease Control and Prevention (CDC) |date=2020-09-17 |lang=en-us |url=https://www.cdc.gov/parasites/guineaworm/gen_info/faqs.html |access-date=2020-10-24}}</ref>

===Animal reservoirs===
In 2020, Guinea worm was found in 1507&nbsp;domestic dogs in Chad, 15 in Ethiopia, and eight in Mali, as well as in 61&nbsp;domestic cats in Chad and three in Ethiopia. Small numbers have also been found in wildcats and baboons.<ref>{{cite press release |title=Guinea worm cases fell 50% in 2020, Carter Center reports |date=26 January 2021 |website=cartercenter.org |publisher=The Carter Center |url=https://www.cartercenter.org/news/pr/2021/guinea-worm-worldwide-cases-announcement-012621.html}}</ref> These findings are a potential problem for the eradication program.

==Epidemiology==
''D. medinensis'' is most commonly found in the [[Earth:Subtropics|subtropic]] to tropical regions, especially in India, [[Place:Western Asia|south-west Asia]] (Iraq, Iran, Pakistan, etc.), and rural areas of Africa, where temperatures between 25 and 30&nbsp;°C are best for larval development.<ref name=Muller-1979>{{cite journal |last=Muller |first=R. |year=1979 |title=Guinea worm disease: Epidemiology, control, and treatment |journal=Bulletin of the World Health Organization |volume=57 |issue=5 |pages=683–689 |pmc=2395878 |pmid=161522}}</ref> The parasite relies on people accidentally consuming microcrustaceans of the genus [[Biology:Cyclops (genus)|''Cyclops'' (copepods)]], that dwell in stationary bodies of water such as ponds, large, open wells (with stairs), or rain-filled [[Engineering:Cistern|cistern]]s.<ref name=Muller-1979/>  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".<ref name=Muller-1979/> This is due to the lower surface water of the stationary bodies of water, which are prime for the growth of the infected [[Biology:Copepod|copepod]]s, and main source of water for many.<ref name=Muller-1979/>

==Pathology==
''D. medinensis'' causes [[Medicine:Dracunculiasis|dracunculiasis]] as a result of the emergence of the female worm, nonemergence of adult worms (usually the male), and secondary bacterial infections.<ref name="Roberts-Janovy-Nadler-2012">{{cite book |last1=Roberts |first1=Larry S. |title=Gerald D. Schmidt & Larry S. Roberts' foundations of parasitology |last2=Janovy |first2=John Jr. |last3=Nadler |first3=Steve |date=2012-11-27 |publisher=McGraw Hill |isbn=978-0-07-352419-1 |edition=9th |place=New York, NY |oclc=812614125}}</ref> As it emerges to the [[Biology:Subcutaneous tissue|subcutaneous tissue]], the female releases a toxic chemical that may result in nausea, rash at site, diarrhea, dizziness, [[Medicine:Edema|localized edema]], reddish papule, blister, and itching.<ref name=Roberts-Janovy-Nadler-2012/> [[Medicine:Arthritis|Arthritis]] or [[Medicine:Paraplegia|paraplegia]] can result from a worm that fails to reach the skin and gets calcified in or along the joint or finds its way into the central nervous tissue.<ref name=Roberts-Janovy-Nadler-2012/> Aseptic abscesses and cystic swelling can also occur when worms rupture before emerging, causing an [[Medicine:Inflammation|acute inflammatory response]] from the host's immune system.<ref name=Roberts-Janovy-Nadler-2012/>

==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.<ref name=CDC-2018-03-16-GWD>{{cite web |title=Management of Guinea worm disease (GWD) |date=2018-03-16 |department=Parasites – Guinea Worm |website=cdc.gov |publisher=U.S. Centers for Disease Control (CDC) |url=https://www.cdc.gov/parasites/guineaworm/treatment.html |access-date=2018-07-22}}</ref> 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.<ref>{{cite book |last=Satin |first=Morton |year=2009 |title=Death in the Pot: The impact of food poisoning on history |publisher=Prometheus Books |place=Amherst, NY |isbn=978-1-61-592224-6 |pages=63–65 |url=https://books.google.com/books?id=kNLZKRObZT8C&q=Rod%20of%20Asclepius&pg=PA63 |via=Google Books}}</ref> 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.<ref name=CDC-2018-03-16-GWD/> 
{{clear}}

==Eradication program==

{| class="wikitable floatright" style="font-size:85%"
|+ Guinea worm cases by year<ref name=CarterCenter>{{cite web |title=Guinea worm case totals |website=cartercenter.org |publisher=The Carter Center |url=https://www.cartercenter.org/health/guinea_worm/case-totals.html}}</ref>
|-
! Year !!  Reported cases !! Countries
|-
| 1986 || estimated {{formatnum:3500000}} || 21<ref name=AP2017/>
|-
| 1989 || 892,055 || 15<ref name=WHOtable><br/>{{cite report |title=Dracunculiasis Epidemiological Data (1989-2008) |website=who.int |publisher=[[Organization:World Health Organization|World Health Organization]] |url=https://www.who.int/dracunculiasis/epidemiology/Epidemiological_data.pdf |access-date=2009-09-14}}</ref>
|-
| 1992 || 374,202 || 15<ref name=WHOtable/>
|-
| 1995 || 129,852 || 19<ref name=WHOtable/>
|-
| 2000 || 75,223 || 16<ref name=WHOtable/>
|-
| 2001 || 63,717 || 16<ref name=WHOtable/>
|-
| 2002 || 54,638 || 14<ref name=WHOtable/>
|-
| 2003 || 32,193 || 13<ref name=WHOtable/>
|-
| 2004 || 16,026 || 13<ref name=WHOtable/>
|-
| 2005 || 10,674 || 12<ref name=WHOtable/>
|-
| 2006 || 25,217 {{efn|1=Increase in reported cases resulted from improved reporting in southern Sudan following the peace agreement in 2005.<ref>{{cite journal | title=Progress toward global eradication of ''Dracunculiasis'', January&nbsp;2005 – May&nbsp;2007 | date=17 August 2007 | journal=Morbidity and Mortality Weekly Report | publisher=U.S. Centers for Disease Control and Prevention (CDC)  | volume=56 | issue=32 | pages=813–817 | pmid=17703170 | url=https://www.cdc.gov/mmwr/preview/mmwrhtml/mm5632a1.htm | access-date= 2011-03-16 | author1=Centers for Disease Control and Prevention (CDC) }}</ref>}} || 10 <ref name=WHOtable/>
|-
| 2007 || 9,585 || 9<ref name=WHOtable/>
|-
| 2008 || 4,619 || 7<ref name=WHOtable/>
|-
| 2009 || 3,190 || 5
|-
| 2010 || 1,797 || 4<ref name=carter2010>{{cite web |title=Guinea worm countdown: The road to eradication |website=cartercenter.org |publisher=The Carter Center |url=http://www.cartercenter.org/health/guinea_worm/mini_site/current.html |access-date=2018-07-22  |archive-url=https://web.archive.org/web/20110906091154/http://www.cartercenter.org/health/guinea_worm/mini_site/current.html |archive-date=2011-09-06}}</ref> (6<ref>{{cite journal |title=Monthly report on dracunculiasis cases, January–December&nbsp;2010 |date=4 March 2011 |publisher=WHO |journal=Weekly Epidemiological Record |volume=86 |issue=10 |page=92 |url=https://www.who.int/wer/2011/wer8610.pdf?ua=1 |access-date=2011-03-04}}</ref>)
|-
| 2011 || 1,060 || 4<ref name=Wrap-up_209>{{cite periodical |title=Wrap-up #209 |date=9 January 2012 |periodical=Guinea Worm Wrap-up |issue=209 |series=WHO Collaborating Center for Research, Training and Eradication of Dracunculiasis |publisher=[[Organization:World Health Organization|World Health Organization]] (WHO) |via=The Carter Center (cartercenter.org) |url=http://www.cartercenter.org/resources/pdfs/news/health_publications/guinea_worm/wrap-up/209.pdf }}</ref>
|-
| 2012 || 542 || 4<ref name=carter2012>{{cite periodical |title=Wrap-up #218 |date=2013-04-22 |periodical=Guinea Worm Wrap-up |issue=218 |series=WHO Collaborating Center for Research, Training and Eradication of Dracunculiasis |publisher=[[Organization:World Health Organization|World Health Organization]] (WHO) |via=The Carter Center (cartercenter.org) |url=https://www.cartercenter.org/resources/pdfs/news/health_publications/guinea_worm/wrap-up/218.pdf |access-date=2022-11-04}}</ref>
|-
| 2013 || 148 || 5<ref name=carter2013>{{cite periodical |title=Wrap-up #226 |date=2014-05-09 |periodical=Guinea Worm Wrap-up |issue=226 |series=WHO Collaborating Center for Research, Training and Eradication of Dracunculiasis |publisher=[[Organization:World Health Organization|World Health Organization]] (WHO) |via=The Carter Center (cartercenter.org) |url=https://www.cartercenter.org/resources/pdfs/news/health_publications/guinea_worm/wrap-up/226.pdf |access-date=2022-11-04}}</ref>
|- 
| 2014 || 126 || 4<ref name=carter2014>{{cite press release |title=126&nbsp;Cases of Guinea worm disease remain worldwide |date=11 January 2015 |website=cartercenter.org |publisher=The Carter Center |url=http://www.cartercenter.org/news/pr/gw-worldwide-cases-Jan2015.html |access-date=2015-05-09}}</ref>
|- 
| 2015 || 22 || 4<ref name=carter2015>{{cite periodical |title=Wrap-up #240 |date=2016-05-13 |periodical=Guinea Worm Wrap-up |issue=240 |series=WHO Collaborating Center for Research, Training and Eradication of Dracunculiasis |publisher=[[Organization:World Health Organization|World Health Organization]] (WHO) |via=The Carter Center (cartercenter.org) |url=https://www.cartercenter.org/resources/pdfs/news/health_publications/guinea_worm/wrap-up/240.pdf |access-date=2022-11-04}}</ref>
|-
| 2016 || 25 || 3<ref name=AP2017>{{cite news |author=Martin, Jeff |date=11 January 2017 |title=Carter: Guinea worm disease reported in 3&nbsp;countries in 2016 |agency=Associated Press |url=http://bigstory.ap.org/article/13da4bec739e4886b06e63175b6a6ebf/carter-guinea-worm-disease-reported-3-countries-2016 |access-date=2017-01-11}}</ref>
|- 
| 2017 || 30 || 2<ref name=carter2017>{{cite press release |title=Announcement for 2017 Guinea worm disease case totals |date=19 January 2018 |website=cartercenter.org |publisher=The Carter Center |url=https://www.cartercenter.org/news/pr/guinea-worm-worldwide-cases-jan2018.html |access-date=2018-07-22 |url-status=live |archive-url=https://web.archive.org/web/20180120173342/https://www.cartercenter.org/news/pr/guinea-worm-worldwide-cases-jan2018.html |archive-date=2018-01-20}}</ref>
|-
| 2018 || 28 || 3<ref>{{cite press release |title=28&nbsp;Guinea worm cases reported in 2018 |date=2019-05-06 |series=Guinea worm update |website=cartercenter.org |publisher=The Carter Center |url=https://www.cartercenter.org/news/features/h/guinea_worm/guinea-worm-update-050619.html}}</ref>
|-
| 2019 || 54 {{efn| Increase over 2018 due to increased reporting, due to cash rewards in Chad for reporting cases.<ref name=Carter-2020-01/>}} || 4<ref name=Carter-2020-01>{{cite press release |title=54* cases of Guinea worm reported in 2019 |date=January 2020 |website=cartercenter.org |publisher=The Carter Center |url=https://www.cartercenter.org/news/pr/2020/guinea-worm-worldwide-cases-jan2020.html}}</ref>
|-
| 2020 || 27 || 6<ref>{{cite press release|title=Guinea worm cases fell 50% in 2020, Carter Center reports |year=2021 |website=cartercenter.org |publisher=The Carter Center |url=https://www.cartercenter.org/news/pr/2021/guinea-worm-worldwide-cases-announcement-012621.html}}</ref>
|-
| 2021 || 15 || 4<ref>{{cite periodical |title=Wrap-up #286 |date=2022-03-31 |periodical=Guinea Worm Wrap-up |issue=286 |series=WHO Collaborating Center for Research, Training and Eradication of Dracunculiasis |publisher=[[Organization:World Health Organization|World Health Organization]] (WHO) |via=The Carter Center (cartercenter.org) |url=https://www.cartercenter.org/resources/pdfs/news/health_publications/guinea_worm/wrap-up/286.pdf |access-date=2023-01-29}}</ref>
|-
| 2022 || 13 || 4<ref>{{Cite web |title=Guinea worm disease reaches all-time low: Only 13*&nbsp;human cases reported in 2022 |date=2023-01-24 |website=The Carter Center |url=https://www.cartercenter.org/news/pr/2023/2022-guinea-worm-worldwide-cases-announcement.html |access-date=2023-01-29}}</ref>
|}

In the 1980s, the [[Organization:Carter Center|Carter Center]] initiated a program to [[Biology:Eradication of infectious diseases|eradicate]] the guinea worm.<ref name=TimeMag-2015-01-23/> The campaign began in 1980 at the U.S. Centers for Disease Control and Prevention. In 1984, the CDC was designated by the [[Organization:World Health Organization|World Health Organization]] as the "Collaborating Center for Research, Training, and Eradication of ''D.&nbsp;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.<ref name=CDC-2017-05-02>{{cite web |title=Eradication program |date=2017-05-02 |department=Parasites – Guinea worm |publisher=U.S. Centers for Disease Control and Prevention |url=https://www.cdc.gov/parasites/guineaworm/gwep.html |access-date=2018-07-22}}</ref> 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.<ref name=TimeMag-2015-01-23>{{cite magazine |title=This species is close to extinction, and that's a good thing |date=23 January 2015 |series=World Science Festival |magazine={{wipe|Time (magazine)}} |url=http://time.com/3680439/guinea-worm-almost-extinct/}}</ref> The International Commission for the Certification of Dracunculus Eradication has certified 198 countries, territories, and other WHO represented areas. As of January&nbsp;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.&nbsp;medinensis'' remain [[Medicine:Endemic (epidemiology)|endemic]] countries.<ref name=CDC-2017-05-02/>

==See also==
* [[Biology:Extinction#Planned extinction|Planned extinction]]

== Explanatory notes==
{{notelist}}

{{clear}}
==References==
{{reflist|25em}}

==External links==
* {{cite news |title=Donors commit $240&nbsp;million to fight neglected diseases |date=2014-04-02 |via=HNKC News |agency=Voice of America |url=http://www.hnkcnews.com/2014/04/02/donors-commit-240-million-to-fight-neglected-diseases/  |access-date=2014-04-04 |archive-url=https://archive.today/20140404210304/http://www.hnkcnews.com/2014/04/02/donors-commit-240-million-to-fight-neglected-diseases/ |archive-date=2014-04-04}}
* {{cite AV media |title=How to Slay a Dragon |type=video documentary |people=Bestall, Clifford |series=Lifelines: The quest for global health |publisher=[[Engineering:Al Jazeera English|Al Jazeera English]] |date=Spring 2014 |quote=47&nbsp;min. |url=http://www.aljazeera.com/programmes/lifelines/2014/04/how-slay-dragon-2014429133319221182.html}}

{{Helminthiases}}
{{Taxonbar|from=Q1502531}}

[[Category:Spirurida]]

{{Sourceattribution|Dracunculus medinensis}}