Geohelminth

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The soil-transmitted helminths (STH,[1] also called geohelminths) 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, causing soil-transmitted helminthiasis, 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.[2][3]

Types[edit]

STHs are caused by four groups of nematodes, namely

Diseases[edit]

Soil-transmitted helminthiasis[edit]

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 controlled/eradicated by 2020 through the London Declaration on Neglected Tropical Diseases.[4]

Strongyloidiasis[edit]

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%).[5][6]

General impact[edit]

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.[3][7]

Interventions and chemotherapy[edit]

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.[8] For this purpose, broad-spectrum benzimidazoles such as mebendazole and albendazole are the drugs of choice recommended by WHO.[9] For stongyloidiasis, ivermectin is the recommended anthelmintic.[6]

See also[edit]

References[edit]

  1. ^ STH is also used to abbreviate soil-transmitted helminthiasis.
  2. ^ Holland CV, Kennedy MW (Eds.) (2002). The Geohelminths: Ascaris, Trichuris and Hookworm. Springer. pp. 1–352. ISBN 978-0-7923-7557-9. 
  3. ^ 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. doi:10.1016/S0140-6736(06)68653-4. PMID 16679166. 
  4. ^ London Declaration (2012) (30 January 2012). "London Declaration on Neglected Tropical Diseases". Retrieved 2013-03-26. 
  5. ^ 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. 
  6. ^ 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. 
  7. ^ WHO. Eliminating Soil-transmitted Helminthiasis as a Public Health Problem in Children: Progress Report 2001–2010 and Strategic Plan 2011–2020. WHO Press, World Health Organization, Geneva, Switzerland. pp. 1–78. ISBN 978-92-4-150312-9. 
  8. ^ 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. 
  9. ^ WHO (2006). Preventive Chemotherapy in Human Helminthiasis : Coordinated Use of Anthelminthic Drugs in Control Interventions : a Manual for Health Professionals and Programme Managers. WHO Press, World Health Organization, Geneva, Switzerland. pp. 1–61. ISBN 9241547103. 

External links[edit]