Medina worm

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Medina worm
Medina worm wound up on a match so that it can be slowly pulled out of a leg vein

Medina worm wound up on a match so that it can be slowly pulled out of a leg vein

Systematics
Order : Spirurida (Spirurida)
Subordination : Camallanina
Superfamily : Dracunculoidea
Family : Dracunculidae
Genre : Dracunculus
Type : Medina worm
Scientific name
Dracunculus medinensis
Linnaeus , 1758

The Guinea worm ( Dracunculus medinensis ) or guinea worm is a parasitic occurring nematode and the causative agent of dracunculiasis . It occurs primarily in humans and mammals when the drinking water hygiene is inadequate, but apart from infected humans, only dogs are of limited epidemiological importance (Dönges 1988). The name Medina worm is derived from the city of Medina in Saudi Arabia.

distribution

The medina worm used to be common in the wetlands of Africa and from Egypt to Pakistan to India . In 1986 there were 3.5 million people infected. Control measures, in particular a prevention campaign by the Carter Center in Atlanta , Georgia , reduced the number of new infections to 25,217 infected people in 2006 and limited the spread to a few areas of Africa, mainly Sudan and Ghana.

At the end of 2009, the WHO identified new infections in Ethiopia, Ghana, Mali and Sudan . In Sudan, the infections occurred only in the south, in what is now South Sudan. Sudan in its current borders was therefore declared free of Medina worms in 2011, as was Ghana. Since 2011, the parasite had mainly been pushed back to South Sudan , with individual occurrences (a few percent of all cases) reported from Ethiopia , Mali and Chad . Occasionally, worms in the human body are carried to other countries in the region. In 2017 human infections were only registered in Chad and Ethiopia (15 each).

While 1060 human infections by the worm were reported in 2011, the number has been below 150 annually since 2013 and below 40 since 2014. In 2015, the infection decreased to 22 cases, but the worm now started around 500 to 1000 dogs annually ( almost exclusively in Chad). In 2017, 30 cases were recorded in humans, around 800 in dogs, and some in baboons. The actual number of living worms, especially in the larval stage, is significantly higher, since mostly only the fully grown and fertilized females at the end of their approximately one-year life in the ultimate host (humans, dogs, baboons) are recorded as infections.

features

There is a strong gender dimorphism . The female becomes 50 to 100 centimeters long at a thickness of about 1 millimeter, the male only 3 to 4 centimeters.

Propagation cycle

Life cycle of Dracunculus medinensis

Copepods , mostly of the genus Cyclops ( hoppers ), act as intermediate hosts necessary for development . Humans ingest the tiny crustaceans infected by worm larvae with their drinking water.

The larvae are released in the stomach, from there they enter the small intestine and penetrate the mucous membrane . In the retroperitoneal space they complete their development and mate. The male then dies and is encapsulated. The fertilized female continues to grow, can be up to a meter long and migrates through the tissue to the extremities, usually to the lower legs or feet. There it settles in the connective tissue of the subcutaneous tissue . This usually causes extreme pain in the affected person. It is not uncommon for fatal complications due to secondary infections to occur without treatment.

The worm's head causes an ulcer the size of a pigeon's egg through excretion . If this comes into contact with water, the thin skin in the center bursts. At the same time, the skin of the worm and its uterus torn close below , releasing thousands of larvae into the water. The uterus then withdraws back into the ulcer and the process is repeated when the water is again wetted. After two to three weeks, the female worm dies.

The larvae are eaten by crabs in the water and bore their way through the intestinal wall into the body cavity in order to develop further. After about two weeks, they are in the third instar and infectious to humans. This closes the cycle of reproduction.

Medina worm and human

The medina worm has been known as a parasite of humans since ancient times and is also mentioned in the canon of medicine of Avicenna from the 11th century. Since 1986, the distribution areas have been severely narrowed. After smallpox and rinderpest , the third disease that could be completely eradicated is dracontiasis.

Pulling the worm out of the body

The traditional way of removing the female worm was and is still done in the endemic areas with a wooden stick. This is used to wind the front end that breaks out of the ulcer a little bit every day, a maximum of 10 centimeters per day, to prevent the worm from tearing through. This type of removal takes a few days, but sometimes many weeks. If this classic removal method fails because the worm tears through, the part of the worm remaining in the wound must be surgically removed to prevent subsequent infections.

Prevention and control

The small crustaceans that Medina worms carry enter humans with untreated drinking water. To remove the crabs from the drinking water, z. B. a finely woven piece of nylon can be used as a filter. Aid organizations such as the Carter Center have been distributing such filter cloths in the villages since 1986 .

Another option is to boil the water or kill the worm-bearing crabs with insecticides. Water can be treated with an approved larvicide, such as Abate , which kills copepods , without putting people or animals at high risk.

Others

In his novel Die Sklavenkarawane Karl May describes a case of illness in which a member of the Abaka tribe has a medina worm ulcer on his face. Removal with a stick is also described.

One hypothesis interprets the classic medical symbol of the Aesculapian staff as a medina worm wound on a wooden stick, which, however, contradicts the worship of the snake among other arguments.

Individual evidence

  1. ↑ a b c Oliver Liesenfeld: Dracunculus medinensis. (online pp. 229–230) Lexicon of infectious diseases in humans. Springer Berlin Heidelberg 2009, pp. 229-231.
  2. ↑ a b Pschyrembel : Clinical Dictionary, 258th edition 1998, keyword Dracunculus medinensis
  3. ↑ Michele Barry: The tail end of Guinea Worm - Global eradication without a drug or a vaccine. In: The New England Journal of Medicine . Vol. 356, No. 25, 2007, ISSN  1533-4406 , pp. 2561-2564 ( article on nejm.org ).
  4. ^ Donald G. Mc Neil: Epidemiology: In Losing Its Southern States to Secession, Sudan Also Sheds Its Guinea Worm Cases. In: The New York Times. July 18, 2011.
  5. ↑ Carter Center, July 28, 2011: Former US President Jimmy Carter Congratulates People of Ghana for Halting Guinea Worm Disease Transmission.
  6. ↑ a b c CDC - Guinea Worm Disease. ( Direct link to PDF ) Retrieved January 30, 2018 (American English).
  7. ^ WHO: In a historical first, WHO records zero cases of dracunculiasis in January
  8. ↑ WHO: Monthly report on dracunculiasis cases, January – December 2012 (PDF; 1.1 MB) in: Weekly epidemiological record No. 9, 2013
  9. ↑ CARTER CENTER: 148 Cases of Guinea Worm Disease Remain Worldwide
  10. ↑ WHO Collaborating Center for Research, Training and Eradication of Dracunculiasis, CDC on October 27, 2014: Guinea worm wrap-up # 229 - CDC on March 6, 2015: Guinea worm wrap-up # 232
  11. ↑ CDC - Guinea Worm Disease. ( Direct link to PDF ) Retrieved January 30, 2018 (American English).
  12. ↑ CDC - Guinea Worm Disease. # 238 - 1/11/2016 English - PDF . In: www.cdc.gov. Retrieved January 30, 2016 (American English).
  13. ↑ Dogs save the Guinea worm www.spektrum.de from January 5, 2016, accessed on January 6, 2016.
  14. ↑ Georg Hieronymus Welsch : Exercitatio de vena Medinensi. Ad mentem Ebnsinae , sive De dracunculis veterum. Augsburg 1674.
  15. ↑ WHO certifies seven more countries as free of guinea-worm disease . The World Health Organization. Retrieved March 28, 2010.
  16. ^ GD Schmidt & L S. Roberts: Larry S. Roberts & John Janovy, Jr. (Eds.): Foundations of Parasitology , 8th. Edition, McGraw-Hill , 2009, ISBN 978-0-07-128458-5 , pp. 480-484.
  17. ↑ ABATE . BASF Agricultural Products. 2006. Retrieved December 2, 2009.
  18. ^ Richard Lucius, Brigitte Loos-Frank: Biology of Parasites. Springer Verlag, 2007, ISBN 978-3540377078 , p. 135.
  19. ^ I. Schiefke et al .: Tropical and Sub- Tropical Helminthoses. In: Der Internist Volume 47, No. 8, 2006, pp. 801-809.
  20. ↑ Helmut Müller: The Aesculapian Staff: Supplements. In: Dtsch Arztebl. Volume 104, No. 9, 2007, A-557 / B-488 / C-470.

Web links

Commons : Dracunculus medinensis  - Collection of images, videos and audio files