View source for Medicine:Soil-transmitted helminthiasis

{{Short description|Roundworm infection contracted from contaminated soil}}
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'''Soil-transmitted helminthiasis''' is a type of worm  infection ([[Medicine:Helminthiasis|helminthiasis]]) caused by different species of [[Biology:Nematode|roundworms]]. It is caused specifically by those worms which are transmitted through soil contaminated with faecal matter and are therefore called soil-transmitted helminths. Three types of soil-transmitted helminthiasis can be distinguished: [[Medicine:Ascariasis|ascariasis]], [[Medicine:Hookworm infection|hookworm infection]] and [[Medicine:Trichuriasis|whipworm infection]]. These three types of infection are therefore caused by the large roundworm ''[[Biology:Ascaris lumbricoides|A. lumbricoides]], ''the hookworms'' [[Biology:Necator americanus|Necator americanus]] ''or'' [[Biology:Ancylostoma duodenale|Ancylostoma duodenale]]'' and by the whipworm ''[[Biology:Trichuris trichiura|Trichuris trichiura]]''.

It has become the most common [[Medicine:Parasitic disease|parasitic disease]] of humans worldwide.<ref>{{Cite journal|last1=Lo|first1=Nathan C.|last2=Heft-Neal|first2=Sam|last3=Coulibaly|first3=Jean T.|last4=Leonard|first4=Leslie|last5=Bendavid|first5=Eran|last6=Addiss|first6=David G.|date=2019-11-01|title=State of deworming coverage and equity in low-income and middle-income countries using household health surveys: a spatiotemporal cross-sectional study|journal=The Lancet Global Health|language=English|volume=7|issue=11|pages=e1511–e1520|doi=10.1016/S2214-109X(19)30413-9|pmc=7024997 |issn=2214-109X|pmid=31558383}}</ref> Approximately two billion people (about a third of global population) are infected as of the latest estimate, and four billion at risk, surpassing even the all-time most prevalent parasitic disease, [[Medicine:Malaria|malaria]].<ref name="WHO2014">{{cite web|title=Soil-transmitted helminth infections Fact sheet N°366|url=https://www.who.int/mediacentre/factsheets/fs366/en/|website=who.int|access-date=18 October 2014|date=April 2014}}</ref> The largest numbers of cases occur in impoverished rural areas of [[Place:Sub-Saharan Africa|Sub-Saharan Africa]], Latin America, [[Place:Southeast Asia|Southeast Asia]], and {{wipe|China}}.<ref name="who">{{cite book|author =WHO|title=Eliminating Soil-transmitted Helminthiasis as a Public Health Problem in Children: Progress Report 2001–2010 and Strategic Plan 2011–2020 |year=2012 |url= http://whqlibdoc.who.int/publications/2012/9789241503129_eng.pdf |publisher= WHO Press, World Health Organization, Geneva, Switzerland |pages=1–78 |isbn= 978-92-4-150312-9}}</ref> Its main cause, like for many types of helminth infections, is lack of [[Engineering:Sanitation|sanitation]], such as the practice of open defecation, lack of hygiene such as hand washing and walking barefoot on contaminated soil.<ref>{{Cite web | url=https://www.cdc.gov/parasites/hookworm/ | title=CDC - Hookworm| date=17 April 2019}}</ref><ref>{{cite journal | vauthors = Ziegelbauer K, Speich B, Mäusezahl D, Bos R, Keiser J, Utzinger J | title = Effect of sanitation on soil-transmitted helminth infection: systematic review and meta-analysis | journal = PLOS Medicine | volume = 9 | issue = 1 | pages = e1001162 | date = January 2012 | pmid = 22291577 | pmc = 3265535 | doi = 10.1371/journal.pmed.1001162 | doi-access = free }}</ref><ref>{{cite journal | vauthors = Strunz EC, Addiss DG, Stocks ME, Ogden S, Utzinger J, Freeman MC | title = Water, sanitation, hygiene, and soil-transmitted helminth infection: a systematic review and meta-analysis | journal = PLOS Medicine | volume = 11 | issue = 3 | pages = e1001620 | date = March 2014 | pmid = 24667810 | pmc = 3965411 | doi = 10.1371/journal.pmed.1001620 | doi-access = free }}</ref> It is regarded as one of the world's most important causes of intellectual and physical retardation.<ref name="bet">{{cite journal | vauthors = Bethony J, Brooker S, Albonico M, Geiger SM, Loukas A, Diemert D, Hotez PJ | s2cid = 8425278 | title = Soil-transmitted helminth infections: ascariasis, trichuriasis, and hookworm | journal = Lancet | volume = 367 | issue = 9521 | pages = 1521–32 | date = May 2006 | pmid = 16679166 | doi = 10.1016/S0140-6736(06)68653-4 }}</ref>

The [[Medicine:Helminthiasis|helminthic disease]] is so named because the infection is transmitted through [[Biology:Ingestion|ingestion]] of the [[Biology:Nematode|nematode]] eggs in the soil, which is contaminated through excrements. Therefore, the disease is most prevalent in warm and moist climates where [[Engineering:Sanitation|sanitation]] and hygiene are poor and waters are unsafe, including the temperate zones during warmer months. STH is categorised among [[Medicine:Neglected tropical diseases|neglected tropical diseases]] because it inflicts tremendous disability and suffering, which can be clinically treated and relatively easily be prevented (primarily through improved sanitation), yet negligible attention has been given for many years.<ref>{{cite web|title=Neglected Tropical Diseases|url=https://www.cdc.gov/globalhealth/ntd/diseases/index.html|website=cdc.gov|access-date=28 November 2014|date=June 6, 2011}}</ref> It is now among the target diseases of ''[[Medicine:London Declaration on Neglected Tropical Diseases|London Declaration on Neglected Tropical Diseases]]'' (launched on 30 January 2012) 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|access-date=2013-03-26}}</ref>

Simple prevention and control strategies are access to improved sanitation, public awareness on personal hygiene and health education.

==Types==
Soil-transmitted helminths are essentially intestinal parasites and their eggs which are liberated along with the faeces of infected persons into the soil. ''Ascaris'' and hookworm eggs become infective as they develop into [[Biology:Larva|larva]]e in soil. Infection occurs when vegetables and fruits, contaminated with soil infested eggs, are consumed; or when hands or fingers have been contaminated with dirt carrying the eggs are put in the mouth. On the other hand, hookworm eggs are not directly infective. They hatch in soil, releasing mobile larvae that can penetrate the skin. Thus infection is acquired through accidental contact with contaminated soil.<ref name=bet />

===Ascariasis===
{{Main|Medicine:Ascariasis}}
[[Image:Ascaris lumbricoides.jpeg|thumb|Female ''Ascaris lumbricoides'']]
Ascariasis of STH is caused by the large roundworm ''[[Biology:Ascaris lumbricoides|A. lumbricoides]]''.  It is estimated to be the most widespread STH, affecting approximately 1 billion people. The victims constitute about half of the populations in tropical and subtropical areas. Most conditions are mild and often show little or no [[Medicine:Symptom|symptom]]s. Heavy infections however are debilitating, causing severe intestinal blockage and impair growth in children. Children, compounded with [[Medicine:Malnutrition|malnutrition]], are most infected, with the most common age group being 3- to 8-year-olds, with an annual death of about 20,000. Children are more susceptible due to their frequent exposure to contaminated environment such as during playing, eating raw vegetables and fruits, and drinking wastewater.<ref name=bet />

=== Hookworm disease ===
{{Main|Medicine:Ancylostomiasis}}
[[Image:hookworms.tif|thumb|left|Hookworm]]
Hookworm infection of STH is caused by ''[[Biology:Necator americanus|N. americanus]]'' and ''[[Biology:Ancylostoma duodenale|A. duodenale]]''. Mild infections produce diarrhoea and [[Medicine:Abdominal pain|abdominal pain]]. More severe infections can create serious health problems for newborns, children, pregnant women, and [[Medicine:Malnutrition|malnourished]] adults. In fact it is the leading cause of anaemia and [[Biology:Protein|protein]] deficiency in developing nations, affected an estimated 740 million people. ''N. americanus'' is the more common hookworm, while ''A. duodenale'' is more geographically restricted. Unlike other STHs, in which school-age children are most affected, high-intensity hookworm infections are more frequent in adults, specifically women. Roughly 44 million pregnant women are estimated to be infected. The disease causes severe adverse effects in both the mother and infant, such as low birth weight, impaired milk production, and increased risk of [[Mortality rate|mortality]].<ref name=bet />

=== Trichuriasis ===
{{Main|Medicine:Trichuriasis}}
[[Image:Trichuris trichiura egg.tif|thumb|''Trichuris trichiura'' egg]]
Whipworm (''[[Biology:Trichuris trichiura|Trichuris trichiura]]'') is the third most common STH-causing nematode in humans. According to current estimate, nearly 800 million people are infected, the majority of them children. Heavy infections could lead to acute symptoms such as diarrhoea and anaemia, and chronic symptoms such as growth retardation and [[Medicine:Intellectual disability|impaired cognitive development]]. Medical conditions are more often serious since [[Medicine:Coinfection|coinfection]] with protozoan parasites such as ''[[Biology:Giardia|Giardia]]'' and ''[[Biology:Entamoeba histolytica|Entamoeba histolytica]]'', and with other nematodes is common.<ref name=bet /> Predominantly a [[Medicine:Tropical disease|tropical disease]] of developing countries, trichuriasis is quite common in the United States.<ref>{{cite journal | vauthors = Starr MC, Montgomery SP | title = Soil-transmitted Helminthiasis in the United States: a systematic review—1940–2010 | journal = The American Journal of Tropical Medicine and Hygiene | volume = 85 | issue = 4 | pages = 680–4 | date = October 2011 | pmid = 21976572 | pmc = 3183777 | doi = 10.4269/ajtmh.2011.11-0214 | url = http://www.ajtmh.org/cgi/pmidlookup?view=long&pmid=21976572 }}</ref>

==Signs and symptoms==
Symptoms becomes evident only when the intensity of infection is relatively high. Thus the degree of negative outcomes is directly related to worm burden; more worms means greater severity of disease.<ref name=":1">{{Cite journal|last1=Hotez|first1=Peter J.|last2=Brindley|first2=Paul J.|last3=Bethony|first3=Jeffrey M.|last4=King|first4=Charles H.|last5=Pearce|first5=Edward J.|last6=Jacobson|first6=Julie|date=2008|title=Helminth infections: the great neglected tropical diseases|journal=The Journal of Clinical Investigation|volume=118|issue=4|pages=1311–1321|doi=10.1172/JCI34261|pmc=2276811|pmid=18382743}}</ref><ref name=":2">{{Cite journal|last=Mascarini-Serra|first=Luciene|date=2011|title=Prevention of Soil-transmitted Helminth Infection|journal=Journal of Global Infectious Diseases|volume=3|issue=2|pages=175–182|doi=10.4103/0974-777X.81696|pmc=3125032|pmid=21731306 |doi-access=free }}</ref><ref>{{Cite journal|last1=Parija|first1=Subhash Chandra|last2=Chidambaram|first2=Meenachi|last3=Mandal|first3=Jharna|date=2017|title=Epidemiology and clinical features of soil-transmitted helminths|journal=Tropical Parasitology|volume=7|issue=2|pages=81–85|doi=10.4103/tp.TP_27_17|doi-broken-date=31 January 2024|doi-access=free|pmc=5652059|pmid=29114484}}</ref>

=== General ===
Most conditions of STH have a light worm burden and usually have no discernible symptoms. Heavy infections however cause a range of health problems, including abdominal pain, diarrhoea, blood and protein loss, [[Medicine:Rectal prolapse|rectal prolapse]], and physical and mental retardation. Severe ascariasis is typically a [[Medicine:Pneumonia|pneumonia]], as the larvae invade [[Medicine:Lung|lung]]s, producing [[Medicine:Fever|fever]], cough and dyspnoea during early stage of infection.<ref>{{Cite journal|last=Ramamoorthy|first=Karthik Ganesh|date=2015|title=Anaesthesia and Ascaris pneumonia (Loeffler's syndrome)|journal=Indian Journal of Anaesthesia|volume=59|issue=2|pages=125–126|doi=10.4103/0019-5049.151379|pmc=4357880|pmid=25788748 |doi-access=free }}</ref><ref name=":3">{{Cite journal|last1=Sarinas|first1=P. S.|last2=Chitkara|first2=R. K.|date=1997|title=Ascariasis and hookworm|url=https://pubmed.ncbi.nlm.nih.gov/9195678|journal=Seminars in Respiratory Infections|volume=12|issue=2|pages=130–137|pmid=9195678}}</ref> Hookworm infections insinuate a skin reaction ([[Medicine:Dermatitis|dermatitis]]), increased white blood cells (eosinophils), a pulmonary reaction ([[Medicine:Pneumonitis|pneumonitis]]), and skin rash (urticarial).<ref name=":3" /><ref>{{Cite journal|last1=Loukas|first1=Alex|last2=Hotez|first2=Peter J.|last3=Diemert|first3=David|last4=Yazdanbakhsh|first4=Maria|last5=McCarthy|first5=James S.|last6=Correa-Oliveira|first6=Rodrigo|last7=Croese|first7=John|last8=Bethony|first8=Jeffrey M.|date=2016|title=Hookworm infection|journal=Nature Reviews|volume=2|pages=16088|doi=10.1038/nrdp.2016.88|pmid=27929101|doi-access=free}}</ref>

Iron deficiency anaemia due to blood loss is a common symptom.<ref name="who2012">{{cite book |author= WHO |year=2012|title= Helminth Control in School-age Children: a Guide for Managers of Control Programmes| url= http://whqlibdoc.who.int/publications/2011/9789241548267_eng.pdf |edition=2 |publisher= WHO Press, World Health Organization, Geneva, Switzerland |pages=1–75 |isbn= 978-92-4-154826-7}}</ref>

=== Malnutrition ===
STH is often associated with [[Medicine:Undernutrition in children|malnutrition in children]] as it worsens their nutritional status in multiple ways.<ref name="WHO2014" /> The worms can induce intestinal bleeding, competition for nutrients (malabsorption of nutrients), frequent anaemia and diarrhoea.<ref name="yap" /> Soil-transmitted helminths can also cause loss of appetite.<ref name="WHO2014" /> These nutritional "knock on" effects of STH can have a significant impact on the mental and physical development of children. In [[Medicine:Endemic (epidemiology)|endemic]] countries, communities remain suppressed due to malnourishment, cognitive disability and physical weaknesses as a result of heavy infections.<ref name=":1" /><ref name=":2" />

==Diagnosis==
For basic diagnosis, specific helminths can be generally identified from the faeces, and their eggs microscopically examined and enumerated using [[Biology:Eggs per gram|fecal egg count method]]. However, there are certain limitations such as the inability to identify [[Medicine:Coinfection|mixed infections]], and on clinical practice, the technique is inaccurate and unreliable.<ref>{{cite journal | vauthors = Humphries D, Nguyen S, Boakye D, Wilson M, Cappello M | s2cid = 34575855 | title = The promise and pitfalls of mass drug administration to control intestinal helminth infections | journal = Current Opinion in Infectious Diseases | volume = 25 | issue = 5 | pages = 584–9 | date = October 2012 | pmid = 22903231 | doi = 10.1097/QCO.0b013e328357e4cf | url = https://zenodo.org/record/1119032 }}</ref><ref>{{cite journal | vauthors = Krauth SJ, Coulibaly JT, Knopp S, Traoré M, N'Goran EK, Utzinger J | title = An in-depth analysis of a piece of shit: distribution of Schistosoma mansoni and hookworm eggs in human stool | journal = PLOS Neglected Tropical Diseases | volume = 6 | issue = 12 | pages = e1969 | year = 2012 | pmid = 23285307 | pmc = 3527364 | doi = 10.1371/journal.pntd.0001969 | doi-access = free }}</ref>
A novel effective method for egg analysis is the Kato–Katz technique. It is a highly accurate and rapid method for ''A. lumbricoides'' and ''T. trichiura''; however not so much for hookworm, which could be due to fast degeneration of the rather delicate hookworm eggs.<ref>{{cite journal | vauthors = Tarafder MR, Carabin H, Joseph L, Balolong E, Olveda R, McGarvey ST | title = Estimating the sensitivity and specificity of Kato-Katz stool examination technique for detection of hookworms, Ascaris lumbricoides and Trichuris trichiura infections in humans in the absence of a 'gold standard' | journal = International Journal for Parasitology | volume = 40 | issue = 4 | pages = 399–404 | date = March 2010 | pmid = 19772859 | pmc = 2829363 | doi = 10.1016/j.ijpara.2009.09.003 }}</ref>

==Prevention==
Prevention and control measures to prevent soil-transmitted helminthiasis are the following: availability of clean water for personal and domestic uses, improved access to [[Engineering:Sanitation|sanitation]] which includes the use of properly functioning and clean toilets by all community members, education on personal hygiene such as hand washing and hygienic and safe food preparation; eliminating the use of untreated human faeces as [[Chemistry:Fertilizer|fertilizer]].<ref name=WHO2014/>

==Treatment==
The World Health Organizations recommended [[Chemistry:Albendazole|albendazole]] or [[Chemistry:Mebendazole|mebendazole]] for treatment.<ref name=WHO2014/>

===Mass treatment with drugs===
One strategy to control the disease in areas where it is common is the treatment of entire groups of people regardless of symptoms via [[Medicine:Mass drug administration|mass drug administration]]. The World Health Organization recommends mass treatments to all at-risk groups in endemic communities, especially women of childbearing age, and children. Mass treatments can also be provided to pregnant women in their second and third trimesters, and breastfeeding women.<ref>{{Cite web|url=https://www.who.int/intestinal_worms/strategy/en/|archive-url=https://web.archive.org/web/20070509152006/http://www.who.int/intestinal_worms/strategy/en/|url-status=dead|archive-date=May 9, 2007|title=WHO {{!}} Strategy|website=WHO|access-date=2019-10-03}}</ref> This known as [[Biology:Mass deworming|mass deworming]].<ref name=WHO2014/><ref>{{cite journal | vauthors = Mascarini-Serra L | title = Prevention of Soil-transmitted Helminth Infection | journal = Journal of Global Infectious Diseases | volume = 3 | issue = 2 | pages = 175–82 | date = April 2011 | pmid = 21731306 | pmc = 3125032 | doi = 10.4103/0974-777X.81696 | doi-access = free }}</ref> While infected treating children is effective, there is significant evidence that concludes that routine deworming, in the absence of a positive test, does not improve nutrition, haemoglobin, school attendance or school performance.<ref>{{Cite journal|last1=Taylor-Robinson|first1=David C.|last2=Maayan|first2=Nicola|last3=Donegan|first3=Sarah|last4=Chaplin|first4=Marty|last5=Garner|first5=Paul|date=11 September 2019|title=Public health deworming programmes for soil-transmitted helminths in children living in endemic areas|journal=The Cochrane Database of Systematic Reviews|volume=9|issue=11|pages=CD000371|doi=10.1002/14651858.CD000371.pub7|issn=1469-493X|pmc=6737502|pmid=31508807}}</ref>

For this purpose, broad-spectrum [[Chemistry:Benzimidazole|benzimidazole]]s such as [[Chemistry:Mebendazole|mebendazole]] and [[Chemistry:Albendazole|albendazole]] are the drugs of choice recommended by WHO. These anthelminthics are safe, inexpensive, and effective for several months. Mebendazole is given twice a day for three consecutive days, while albendazole is given as a single dose. WHO recommends annual treatment in areas where between 20 and 50% of people are infected, and a twice a year treatment if it is over 50%; and in low risk situations (i.e. less than 20% prevalence) case-by-case treatment.<ref name=who2012 /><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 |publisher= WHO Press, World Health Organization, Geneva, Switzerland |pages=1–61 |isbn= 978-9241547109}}</ref> In addition to these, pyrantel pamoate is also equally effective on ascaris. However, it has been reported that albendazole, mebendazole, and pyrantel pamoate are not entirely effective against ''T. trichiura'' with single oral doses in population-based control.<ref>{{cite journal | vauthors = Keiser J, Utzinger J | title = Efficacy of current drugs against soil-transmitted helminth infections: systematic review and meta-analysis | journal = JAMA | volume = 299 | issue = 16 | pages = 1937–48 | date = April 2008 | pmid = 18430913 | doi = 10.1001/jama.299.16.1937 }}</ref>

===Drugs for those with other diseases===
In cases of coinfection, combination therapy with [[Chemistry:Ivermectin|ivermectin]] and [[Chemistry:Diethylcarbamazine|diethylcarbamazine]] is advocated. However coinfection with [[Medicine:Malaria|malaria]] and [[Biology:HIV|HIV]], especially among African women, does not respond well to the current combination therapies.<ref>{{cite journal | vauthors = Ivan E, Crowther NJ, Rucogoza AT, Osuwat LO, Munyazesa E, Mutimura E, Njunwa KJ, Zambezi KJ, Grobusch MP | title = Malaria and helminthic co-infection among HIV-positive pregnant women: prevalence and effects of antiretroviral therapy | journal = Acta Tropica | volume = 124 | issue = 3 | pages = 179–84 | date = December 2012 | pmid = 22940013 | doi = 10.1016/j.actatropica.2012.08.004 }}</ref> It is more pressing for trichuriasis that the recommended drugs fail to provide positive results.<ref>{{cite journal | vauthors = Speich B, Ame SM, Ali SM, Alles R, Hattendorf J, Utzinger J, Albonico M, Keiser J | title = Efficacy and safety of nitazoxanide, albendazole, and nitazoxanide-albendazole against Trichuris trichiura infection: a randomized controlled trial | journal = PLOS Neglected Tropical Diseases | volume = 6 | issue = 6 | pages = e1685 | year = 2012 | pmid = 22679525 | pmc = 3367984 | doi = 10.1371/journal.pntd.0001685 | doi-access = free }}</ref> A novel drug [[Chemistry:Tribendimidine|tribendimidine]], which was approved in China by the [[Organization:Chinese Center for Disease Control and Prevention|CCDC]] for human use in 2004, has been subjected to [[Engineering:Clinical trial|clinical trial]]s showing that they are highly effective against major human [[Biology:Trematoda|flukes]], ascaris (>90% cure rate) and hookworm (>82%); however with low cure rate for whipworm (<37%).<ref>{{cite journal | vauthors = Xiao SH, Utzinger J, Tanner M, Keiser J, Xue J | title = Advances with the Chinese anthelminthic drug tribendimidine in clinical trials and laboratory investigations | journal = Acta Tropica | volume = 126 | issue = 2 | pages = 115–26 | date = May 2013 | pmid = 23352956 | doi = 10.1016/j.actatropica.2013.01.009 }}</ref>

=== Surgical intervention ===
In some severe cases of ascariasis the numbers of Ascaris worms can cause [[Medicine:Bowel obstruction|intestinal obstruction]] requiring emergency surgery.<ref name=Hef2009/> The obstruction may be due to a collected mass of worms or to a [[Medicine:Volvulus|twisting of the intestine]].<ref name=Hef2009/> During the surgery the worms may be manually removed.<ref name=Hef2009>{{cite journal | vauthors = Hefny AF, Saadeldin YA, Abu-Zidan FM | title = Management algorithm for intestinal obstruction due to ascariasis: a case report and review of the literature | journal = Ulusal Travma ve Acil Cerrahi Dergisi = Turkish Journal of Trauma & Emergency Surgery | volume = 15 | issue = 3 | pages = 301–5 | date = May 2009 | pmid = 19562557 }}</ref>

==Epidemiology==

=== Regions ===
Infections are widely distributed in tropical and subtropical areas, with the greatest numbers occurring in sub-Saharan Africa, the Americas, China and east Asia.<ref name="WHO2014" />

=== Infection estimates ===
The World Health Organization estimates that globally more than 1.5 billion people (24% of the total population) have a soil-transmitted helminth infection.<ref name="WHO2014" /> Over 270 million preschool-age children and over 600 million school-age children live in areas where these parasites are intensively transmitted, and are in need of treatment and preventive interventions. Latest estimates indicate that more than 880 million children are in need of treatment from STH infections.<ref name="who" /><ref name="yap" /><ref name=":0" />

By type of parasitic worm the breakdown is:<ref>{{cite journal | vauthors = Hotez PJ, Fenwick A, Savioli L, Molyneux DH | s2cid = 18371227 | title = Rescuing the bottom billion through control of neglected tropical diseases | journal = Lancet | volume = 373 | issue = 9674 | pages = 1570–5 | date = May 2009 | pmid = 19410718 | doi = 10.1016/S0140-6736(09)60233-6 }}</ref>
* approximately 807–1,121 million with [[Biology:Ascaris|ascaris]]
* approximately 576–740 million with [[Biology:Hookworm|hookworm]]
* approximately 604–795 million with whipworm

=== Deaths ===
Latest estimates indicate that the total annual death toll which is directly attributable is as high as 135,000.<ref name="who" /><ref name="yap">{{cite journal | vauthors = Yap P, Fürst T, Müller I, Kriemler S, Utzinger J, Steinmann P | title = Determining soil-transmitted helminth infection status and physical fitness of school-aged children | journal = Journal of Visualized Experiments | volume = 66 | issue = 66 | pages = e3966 | date = August 2012 | pmid = 22951972 | pmc = 3486755 | doi = 10.3791/3966 }}</ref><ref name=":0">{{cite journal | vauthors = Lustigman S, Prichard RK, Gazzinelli A, Grant WN, Boatin BA, McCarthy JS, Basáñez MG | title = A research agenda for helminth diseases of humans: the problem of helminthiases | journal = PLOS Neglected Tropical Diseases | volume = 6 | issue = 4 | pages = e1582 | year = 2012 | pmid = 22545164 | pmc = 3335854 | doi = 10.1371/journal.pntd.0001582 | doi-access = free }}</ref> The death toll due to the malnutrition link is likely to be much higher.<ref>{{Cite journal|last1=Sangalang|first1=Stephanie O.|last2=Medina|first2=Shelley Anne J.|last3=Ottong|first3=Zheina J.|last4=Lemence|first4=Allen Lemuel G.|last5=Totanes|first5=Donrey|last6=Valencia|first6=John Cedrick|last7=Singson|first7=Patricia Andrea A.|last8=Olaguera|first8=Mikaela|last9=Prado|first9=Nelissa O.|last10=Ocaña|first10=Roezel Mari Z.|last11=Canja|first11=Rovin James F.|date=2020-12-30|title=Protocol for a Trial Assessing the Impacts of School-Based WaSH Interventions on Children's Health Literacy, Handwashing, and Nutrition Status in Low- and Middle-Income Countries|journal=International Journal of Environmental Research and Public Health|volume=18|issue=1|pages=226|doi=10.3390/ijerph18010226|pmc=7795080|pmid=33561075|doi-access=free}}</ref><ref>{{Cite journal|last1=Muslim|first1=Azdayanti|last2=Lim|first2=Yvonne Ai-Lian|last3=Mohd Sofian|first3=Sakinah|last4=Shaari|first4=Syahrul Azlin|last5=Mohd Zain|first5=Zaini|date=2021|title=Nutritional status, hemoglobin level and their associations with soil-transmitted helminth infections between Negritos (indigenous) from the inland jungle village and resettlement at town peripheries|journal=PLOS ONE|volume=16|issue=1|pages=e0245377|doi=10.1371/journal.pone.0245377|pmc=7806132|pmid=33439889|bibcode=2021PLoSO..1645377M|doi-access=free}}</ref>

== References ==
{{Reflist|30em}}

== External links ==
* [https://www.cdc.gov/parasites/sth/ Centers for Disease Control and Prevention]
* [https://web.archive.org/web/20130413030844/http://www.who.int/intestinal_worms/more/en/index.html WHO information page]

{{Helminthiases}}

[[Category:Helminthiases]]
[[Category:Tropical diseases]]
[[Category:Parasitic diseases]]

{{Sourceattribution|Soil-transmitted helminthiasis}}