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'''Geohelminths''' (or more frequently '''soil-transmitted helminths''', '''STHs'''] are a group of [[intestinal parasite]]s belonging to the [[class (biology)|class]] [[Nematoda]] that are transmitted primarily through contaminated soil. They are so called because they have a direct [[life cycle (biology)|life cycle]] which requires no [[intermediate host]]s or [[vector (epidemiology)|vectors]], and the [[parasitic infection]] occurs through [[faeces|faecal]] contamination of soil, foodstuffs and water supplies. The adult forms are essentially [[parasites]] of humans, but also infect [[domestication|domesticated]] [[mammals]]. The [[juvenile (organism)| juveniles]] are the infective forms and they undergo tissue-migratory stages during which they invade vital organs such as [[lungs]] and [[liver]]. Thus the disease manifestations can be both local and systemic. The geohelminths together present an enormous infection burden on humanity, amounting to 135,000 deaths every year, and persistent infection of more than two billion people.<ref name=hol>{{cite book|author=Holland CV, Kennedy MW (Eds.)|title= The Geohelminths: ''Ascaris'', ''Trichuris'' and Hookworm|year= 2002|page= 1-352 |ISBN =0792375579|publisher= Springer}}</ref><ref name=bet>{{cite journal|author=Bethony J, Brooker S, Albonico M, Geiger SM, Loukas A, Diemert D, Hotez PJ|year=2006 |pmid=16679166 |title=Soil-transmitted helminth infections: ascariasis, trichuriasis, and hookworm| url=http://linkinghub.elsevier.com/retrieve/pii/S0140-6736(06)68653-4|journal=The Lancet|volume=367|issue=9521 |pages=1521–1532|doi=}}</ref>
{{Unreferenced|date=December 2009}}
{{Orphan|date=February 2009}}
'''Geohelminths''' are soil-transmitted [[parasite|parasitic]] [[nematode]]s with a life cycle that involves no intermediate hosts or vectors: they infect many animals, including humans, and are spread by the faecal contamination of soil, foods and water. Most species have juvenile forms which move around the body of the host, but all species inhabit the intestine in their adult stages and release their eggs in the host's faeces. The diseases they cause can thus be local or systemic.


==Types==
Four species cause widespread disease in humans: ''[[Ascaris lumbricoides]]'' (the large roundworm, which causes [[ascariasis]]), ''[[Trichuris trichiura]]'' (the whipworm, which causes [[trichuriasis]]), and the blood-feeding [[hookworm]]s ''[[Ancylostoma duodenale]]'' and ''[[Necator americanus]]'', which cause [[ankylostomiasis]].


STHs are caused by four groups of [[nematode]]s, namely
⚫
Geohelminth infection is a major health problem of children from rural areas of developing countries like [[India]]. It is an important cause of morbidity in school age children who harbour the highest intensity of worm infestation. Some of the significant morbidity attributed to intestinal [[helminthiasis]] is malnutrition, growth retardation, [[anemia]], [[Nyctalopia|vitamin A deficiency]] and impaired intellectual performance. Thus, [[hookworm]] poses a serious threat to developing countries trying to raise their level of education.
*ascaris (''[[Ascaris lumbricoides]]'')
*whipworm (''[[Trichuris trichiura]]'')
*hookworms (''[[Ancylostoma duodenale]]'' and ''[[Necator americanus]]'')
*pinworm/threadworm ''[[Strongyloides stercoralis]]''

==Diseases==

===Soil-transmitted helminthiasis===
{{Main| Soil-transmitted helminthiasis}}
Soil-transmitted helminthiasis (STH) is a collective name for the diseases caused by ascaris, whipworm and hookworms in humans. It includes species-specific diseases such as
*[[ascariasis]], which is caused by ''[[Ascaris lumbricoides|A. lumbricoides]]''
*[[hookworm disease]]s ([[ancylostomiasis]] and [[necatoriasis]]), which are caused by ''[[Necator americanus|N. americanus]]'' and ''[[Ancylostoma duodenale|A. duodenale]]''
*[[trichuriasis]], which is caused by ''[[Trichuris trichiura |T. trichiura]]''
STH is classified as one of the [[neglected tropical diseases]] projected to be to be controlled/eradicated by 2020.<ref>{{cite web|author = London Declaration (2012)|url= http://www.dfid.gov.uk/Documents/publications1/NTD%20Event%20-%20London%20Declaration%20on%20NTDs.pdf |title=London Declaration on Neglected Tropical Diseases|date= 30 January 2012|accessdate=2013-3-26}}</ref>

===Strongyloidiasis===
{{Main| Strongyloidiasis}}
This is caused by [[Strongyloides stercoralis|''S. stercoralis]]. Even though the disease is principally a STH, the infection being mediated through soil, it is however generally omitted in clinical practices and control programmes because of its (allegedly) relatively less significant influence on health and socio-economic conditions. Also it is not restricted to humans, as it is common in [[pet |pets]]. But there is an emerging hyperinfection syndrome caused by ''S. stercoralis'', which exhibits a high [[mortality rate]] (15% to 87%).<ref>{{cite journal|author=Marcos LA, Terashima A, Dupont HL, Gotuzzo E|year=2013 |pmid=18321548 |title=Strongyloides hyperinfection syndrome: an emerging global infectious disease| url= |journal=Trans R Soc Trop Med Hyg|volume=102|issue=4 |pages=314-318|doi=10.1016/j.trstmh.2008.01.020}}</ref><ref name=buo>{{cite journal|author=Buonfrate D, Requena-Mendez A, Angheben A, Muñoz J, Gobbi F, Van Den Ende J, Bisoffi Z|year=2013 |pmid=23394259 |pmc= PMC3598958|title=Severe strongyloidiasis: a systematic review of case reports| url= |journal=BMC Infect Dis|volume=13|issue= |pages=78|doi=10.1186/1471-2334-13-78}}</ref>

==General Impact==
⚫
Geohelminth infection is a major health problem particularly in [[rural|rural areas]] of [[developing countries]] like [[Subsaharan Africa]], [[India]] and other [[Southeast Asia]]n countries. It is an important cause of [[disease|morbidity]] in [[school age]] children who harbour the highest intensity of worm infestation. Some of the significant morbidity attributed to intestinal [[helminthiasis]] are [[malnutrition]], [[growth retardation]], [[anaemia]], [[Nyctalopia|vitamin A deficiency]] and [[mental retardation|impaired intellectual performance]].<ref name=bet></ref><ref>{{cite book|author =WHO|year= |title=Eliminating Soil-transmitted Helminthiasis as a Public Health Problem in Children: Progress Report 2001–2010 and Strategic Plan 2011–2020 |url= http://whqlibdoc.who.int/publications/2012/9789241503129_eng.pdf |publisher= WHO Press, World Health Organization, Geneva, Switzerland |pages=1-78 |isbn= 9241503129}}</ref>

==Interventions and Chemotherapy==

Prevention of infection is mainly based on [[sanitation]], such as clean water, personal [[hygiene]], and avoiding the use of uncomposted human faeces as [[fertilizer]]. The most important strategy of intervention involves [[mass drug administration]], especially among school-age children.<ref>{{cite journal|author= Mascarini-Serra L|year=2011 |pmc=PMC3125032|pmid= 21731306|title= Prevention of soil-transmitted helminth infection | journal= Journal of Global Infectious Diseases | volume= 3 |issue=2 |pages= 175-182|url=http://www.jgid.org/article.asp?issn=0974-777X;year=2011;volume=3;issue=2;spage=175;epage=182;aulast=Mascarini%2DSerra| doi=10.4103/0974-777X.81696}}</ref> For this purpose, broad-spectrum [[benzimidazole]]s such as [[mebendazole]] and [[albendazole]] are the drugs of choice recommended by [[WHO]].<ref>{{cite book |author= WHO |year=2006|title= Preventive Chemotherapy in Human Helminthiasis : Coordinated Use of Anthelminthic Drugs in Control Interventions : a Manual for Health Professionals and Programme Managers| url= http://whqlibdoc.who.int/publications/2006/9241547103_eng.pdf |edition= |publisher= WHO Press, World Health Organization, Geneva, Switzerland |pages=1-61 |isbn= 9241547103}}</ref> For stongyloidiasis, [[ivermectin]] is the recommended [[anthelmintic]].<ref name=buo></ref>

==See also==

*[[Helminthiasis]]

==References==
{{Reflist}}

==External Links==

*[http://www.cdc.gov/globalhealth/ntd/diseases/sth_burden.html Centers for Disease Control and Prevention]
*[http://www.who.int/intestinal_worms/more/en/index.html WHO information page]
*[http://www.who.int/neglected_diseases/diseases/strongyloidiasis/en/ WHO information on strongyloidiasis]
*[http://www.uptodate.com/contents/strongyloidiasis Strongyloidiasis at UpToDate (Wolters Kluwer Health]
*[http://iceh.uws.edu.au/fact_sheets/FS_strongyloidiasis.html ICEH Resources Information Sheet on strongyloidiasis]
*[http://www.neglecteddiseases.gov/target_diseases/soil_transmitted_helminthiasis/ USAID's NTD Program]
*[http://www.unitingtocombatntds.org/endorsements London Declaration Uniting to Combat NTDs]
*[http://www.rightdiagnosis.com/h/helminthiasis/intro.htm Information at Right Diagnosis]
*[http://www.neglecteddiseases.gov/target_diseases/index.html USAID's Neglected Tropical Diseases Programme]
*[http://www.shinpoong.co.kr/tddc/Soil/soil-intro.htm Types of soil-transmitted helminths at Shinpoong]


[[Category:Nematodes]]
[[Category:Nematodes]]
[[Category:Parasites]]
[[Category:Parasites]]
[[Category:Neglected diseases]]
[[Category:Intestinal infectious diseases]]
[[Category:Parasitic diseases]]

Revision as of 04:32, 29 March 2013

Geohelminths (or more frequently soil-transmitted helminths, STHs] are a group of intestinal parasites belonging to the class Nematoda that are transmitted primarily through contaminated soil. They are so called because they have a direct life cycle which requires no intermediate hosts or vectors, and the parasitic infection occurs through faecal contamination of soil, foodstuffs and water supplies. The adult forms are essentially parasites of humans, but also infect domesticated mammals. The juveniles are the infective forms and they undergo tissue-migratory stages during which they invade vital organs such as lungs and liver. Thus the disease manifestations can be both local and systemic. The geohelminths together present an enormous infection burden on humanity, amounting to 135,000 deaths every year, and persistent infection of more than two billion people.[1][2]

Types

STHs are caused by four groups of nematodes, namely

Diseases

Soil-transmitted helminthiasis

Main article: Soil-transmitted helminthiasis

Soil-transmitted helminthiasis (STH) is a collective name for the diseases caused by ascaris, whipworm and hookworms in humans. It includes species-specific diseases such as

STH is classified as one of the neglected tropical diseases projected to be to be controlled/eradicated by 2020.[3]

Strongyloidiasis

Main article: Strongyloidiasis

This is caused by S. stercoralis. Even though the disease is principally a STH, the infection being mediated through soil, it is however generally omitted in clinical practices and control programmes because of its (allegedly) relatively less significant influence on health and socio-economic conditions. Also it is not restricted to humans, as it is common in pets. But there is an emerging hyperinfection syndrome caused by S. stercoralis, which exhibits a high mortality rate (15% to 87%).[4][5]

General Impact

Geohelminth infection is a major health problem particularly in rural areas of developing countries like Subsaharan Africa, India and other Southeast Asian countries. It is an important cause of morbidity in school age children who harbour the highest intensity of worm infestation. Some of the significant morbidity attributed to intestinal helminthiasis are malnutrition, growth retardation, anaemia, vitamin A deficiency and impaired intellectual performance.[2][6]

Interventions and Chemotherapy

Prevention of infection is mainly based on sanitation, such as clean water, personal hygiene, and avoiding the use of uncomposted human faeces as fertilizer. The most important strategy of intervention involves mass drug administration, especially among school-age children.[7] For this purpose, broad-spectrum benzimidazoles such as mebendazole and albendazole are the drugs of choice recommended by WHO.[8] For stongyloidiasis, ivermectin is the recommended anthelmintic.[5]

See also

References

  1. ^ Holland CV, Kennedy MW (Eds.) (2002). The Geohelminths: Ascaris, Trichuris and Hookworm. Springer. p. 1-352. ISBN 0792375579. {{cite book}}: Check |isbn= value: checksum (help)
  2. ^ a b Bethony J, Brooker S, Albonico M, Geiger SM, Loukas A, Diemert D, Hotez PJ (2006). "Soil-transmitted helminth infections: ascariasis, trichuriasis, and hookworm". The Lancet. 367 (9521): 1521–1532. PMID 16679166.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  3. ^ London Declaration (2012) (30 January 2012). "London Declaration on Neglected Tropical Diseases" (PDF). Retrieved 2013-3-26. {{cite web}}: Check date values in: |accessdate= (help)CS1 maint: numeric names: authors list (link)
  4. ^ Marcos LA, Terashima A, Dupont HL, Gotuzzo E (2013). "Strongyloides hyperinfection syndrome: an emerging global infectious disease". Trans R Soc Trop Med Hyg. 102 (4): 314–318. doi:10.1016/j.trstmh.2008.01.020. PMID 18321548.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  5. ^ a b Buonfrate D, Requena-Mendez A, Angheben A, Muñoz J, Gobbi F, Van Den Ende J, Bisoffi Z (2013). "Severe strongyloidiasis: a systematic review of case reports". BMC Infect Dis. 13: 78. doi:10.1186/1471-2334-13-78. PMC 3598958. PMID 23394259.{{cite journal}}: CS1 maint: PMC format (link) CS1 maint: multiple names: authors list (link) CS1 maint: unflagged free DOI (link)
  6. ^ WHO. Eliminating Soil-transmitted Helminthiasis as a Public Health Problem in Children: Progress Report 2001–2010 and Strategic Plan 2011–2020 (PDF). WHO Press, World Health Organization, Geneva, Switzerland. pp. 1–78. ISBN 9241503129. {{cite book}}: Check |isbn= value: checksum (help)
  7. ^ Mascarini-Serra L (2011). "Prevention of soil-transmitted helminth infection". Journal of Global Infectious Diseases. 3 (2): 175–182. doi:10.4103/0974-777X.81696. PMC 3125032. PMID 21731306.{{cite journal}}: CS1 maint: PMC format (link) CS1 maint: unflagged free DOI (link)
  8. ^ WHO (2006). Preventive Chemotherapy in Human Helminthiasis : Coordinated Use of Anthelminthic Drugs in Control Interventions : a Manual for Health Professionals and Programme Managers (PDF). WHO Press, World Health Organization, Geneva, Switzerland. pp. 1–61. ISBN 9241547103.

External Links

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