Helminthiasis

File:Ascariasis LifeCycle - CDC Division of Parasitic Diseases.png

File:Collage Helminth eggs.png with larva hatching, sample of adult roundworms, Hymenolepis nana, Schistosoma mansoni and Toxocara canis with larva hatching]]

Of all the known helminth species, the most important helminths with respect to understanding their transmission pathways, their control, inactivation and enumeration in samples of human excreta from dried feces, faecal sludge, wastewater, and sewage sludge are:{{Cite journal |vauthors=Maya C, Torner-Morales FJ, Lucario ES, Hernández E, Jiménez B |date=October 2012 |title=Viability of six species of larval and non-larval helminth eggs for different conditions of temperature, pH and dryness |journal=Water Research |volume=46 |issue=15 |pages=4770–82 |doi=10.1016/j.watres.2012.06.014 |pmid=22794801|bibcode=2012WatRe..46.4770M }}

• soil-transmitted helminths, including Ascaris lumbricoides (the most common worldwide), Trichuris trichiura, Necator americanus, Strongyloides stercoralis and Ancylostoma duodenale
• Hymenolepis nana
• Taenia saginata
• Enterobius
• Fasciola hepatica
• Schistosoma mansoni
• Toxocara canis
• Toxocara cati

Helminthiases are classified as follows (the disease names end with "-sis" and the causative worms are in brackets):

• Filariasis (Wuchereria bancrofti, Brugia malayi infection)
• Onchocerciasis (Onchocerca volvulus infection)
• Soil-transmitted helminthiasis – this includes ascariasis (Ascaris lumbricoides infection), trichuriasis (Trichuris infection), and hookworm infection (includes necatoriasis and Ancylostoma duodenale infection)
• Trichostrongyliasis (Trichostrongylus spp. infection)
• Dracunculiasis (guinea worm infection)
• Baylisascaris (raccoon roundworm, may be transmitted to pets, livestock, and humans)

• Echinococcosis (Echinococcus infection)
• Hymenolepiasis (Hymenolepis infection)
• Taeniasis/cysticercosis (Taenia infection)
• Coenurosis (T. multiceps, T. serialis, T. glomerata, and T. brauni infection)

• Amphistomiasis (amphistomes infection)
• Clonorchiasis (Clonorchis sinensis infection)
• Fascioliasis (Fasciola infection)
• Fasciolopsiasis (Fasciolopsis buski infection)
• Opisthorchiasis (Opisthorchis infection)
• Paragonimiasis (Paragonimus infection)
• Schistosomiasis/bilharziasis (Schistosoma infection)

• Moniliformis infection

File:4951113771 b76622322c bdracunculose.jpg), worm coming out of the foot of an infected person.]]

File:Ascaris infection- Antimesenteric splitting of the outer layers of the bowel wall due to a large amount of ascaris (South Africa) (15806559913).jpg

The signs and symptoms of helminthiasis depend on a number of factors including: the site of the infestation within the body; the type of worm involved; the number of worms and their volume; the type of damage the infesting worms cause; and, the immunological response of the body. Where the burden of parasites in the body is light, there may be no symptoms.{{citation needed|date=January 2021}}

Certain worms may cause particular constellations of symptoms. For instance, taeniasis can lead to seizures due to neurocysticercosis.{{Cite journal |vauthors=Del Brutto OH |year=2012 |title=Neurocysticercosis: a review |journal=TheScientificWorldJournal |volume=2012 |pages=159821 |doi=10.1100/2012/159821 |pmc=3261519 |pmid=22312322 |doi-access=free }}

In extreme cases of intestinal infestation, the mass and volume of the worms may cause the outer layers of the intestinal wall, such as the muscular layer, to tear. This may lead to peritonitis, volvulus, and gangrene of the intestine.{{Cite journal |vauthors=Madiba TE, Hadley GP |date=February 1996 |title=Surgical management of worm volvulus |journal=South African Journal of Surgery. Suid-Afrikaanse Tydskrif vir Chirurgie |volume=34 |issue=1 |pages=33–5; discussion 35–6 |pmid=8629187}}

As pathogens in the body, helminths induce an immune response. Immune-mediated inflammatory changes occur in the skin, lung, liver, intestine, central nervous system, and eyes. Signs of the body's immune response may include eosinophilia, edema, and arthritis.{{Cite journal |vauthors=Minciullo PL, Cascio A, David A, Pernice LM, Calapai G, Gangemi S |date=October 2012 |title=Anaphylaxis caused by helminths: review of the literature |journal=European Review for Medical and Pharmacological Sciences |volume=16 |issue=11 |pages=1513–8 |pmid=23111963}} An example of the immune response is the hypersensitivity reaction that may lead to anaphylaxis. Another example is the migration of Ascaris larvae through the bronchi of the lungs causing asthma.{{Cite book |title=Markell and Vogue's Medical Parasitology, 9th Edition |vauthors=John DT, William Jr AP |publisher=Saunders Elsevier Press |year=2006 |isbn=0721647936}}

{{See also|Effects of parasitic worms on the immune system}}

File:Helminth in appendix 20x.jpg showing a pin worm.]]

In humans, T helper cells and eosinophils respond to helminth infestation. It is well established that T helper 2 cells are the central players of protective immunity to helminths,{{Cite journal |vauthors=Cortés A, Muñoz-Antoli C, Esteban JG, Toledo R |date=September 2017 |title=Th2 and Th1 Responses: Clear and Hidden Sides of Immunity Against Intestinal Helminths |url=https://doi.org/10.1016/j.pt.2017.05.004 |journal=Trends in Parasitology |volume=33 |issue=9 |pages=678–693 |doi=10.1016/j.pt.2017.05.004 |pmid=28566191|url-access=subscription }} while the roles for B cells and antibodies are context-dependent.{{Cite journal |vauthors=Zaini A, Good-Jacobson KL, Zaph C |date=May 2021 |title=Context-dependent roles of B cells during intestinal helminth infection |journal=PLOS Neglected Tropical Diseases |volume=15 |issue=5 |pages=e0009340 |doi=10.1371/journal.pntd.0009340 |pmc=8118336 |pmid=33983946 |doi-access=free }} Inflammation leads to encapsulation of egg deposits throughout the body. Helminths excrete into the intestine toxic substances after they feed. These substances then enter the circulatory and lymphatic systems of the host body.{{citation needed|date=January 2021}}

Chronic immune responses to helminthiasis may lead to increased susceptibility to other infections such as tuberculosis, HIV, and malaria.{{Cite journal |vauthors=van Riet E, Hartgers FC, Yazdanbakhsh M |year=2007 |title=Chronic helminth infections induce immunomodulation: consequences and mechanisms |journal=Immunobiology |volume=212 |issue=6 |pages=475–90 |doi=10.1016/j.imbio.2007.03.009 |pmid=17544832}}{{Cite journal |vauthors=Mkhize-Kwitshana ZL, Mabaso MH |date=June 2012 |title=Status of medical parasitology in South Africa: new challenges and missed opportunities |journal=Trends in Parasitology |volume=28 |issue=6 |pages=217–9 |doi=10.1016/j.pt.2012.03.005 |pmid=22525798}}{{Cite journal |vauthors=Borkow G, Bentwich Z |year=2000 |title=Eradication of helminthic infections may be essential for successful vaccination against HIV and tuberculosis |url=http://www.scielosp.org/scielo.php?pid=S0042-96862000001100013&script=sci_arttext |journal=Bulletin of the World Health Organization |volume=78 |issue=11 |pages=1368–9 |pmc=2560630 |pmid=11143198 |hdl=10665/268007}} There is conflicting information about whether deworming reduces HIV progression and viral load and increases CD4 counts in antiretroviral naive and experienced individuals, although the most recent Cochrane review found some evidence that this approach might have favorable effects.{{Cite journal |display-authors=6 |vauthors=Lankowski AJ, Tsai AC, Kanyesigye M, Bwana M, Haberer JE, Wenger M, Martin JN, Bangsberg DR, Hunt PW, Siedner MJ |date=August 2014 |title=Empiric deworming and CD4 count recovery in HIV-infected Ugandans initiating antiretroviral therapy |journal=PLOS Neglected Tropical Diseases |volume=8 |issue=8 |pages=e3036 |doi=10.1371/journal.pntd.0003036 |pmc=4125278 |pmid=25101890 |doi-access=free }}{{Cite journal |vauthors=Means AR, Burns P, Sinclair D, Walson JL |date=April 2016 |title=Antihelminthics in helminth-endemic areas: effects on HIV disease progression |journal=The Cochrane Database of Systematic Reviews |volume=2016 |issue=4 |pages=CD006419 |doi=10.1002/14651858.CD006419.pub4 |pmc=4963621 |pmid=27075622}} Helminth infection also lowers the immune responses to vaccination for other diseases such as BCG, measles, and Hepatitis B.{{Cite journal |last1=Natukunda |first1=Agnes |last2=Zirimenya |first2=Ludoviko |last3=Nassuuna |first3=Jacent |last4=Nkurunungi |first4=Gyaviira |last5=Cose |first5=Stephen |last6=Elliott |first6=Alison M. |last7=Webb |first7=Emily L. |date=17 June 2022 |title=The effect of helminth infection on vaccine responses in humans and animal models: A systematic review and meta-analysis |journal=Parasite Immunology |language=en |volume=44 |issue=9 |pages=e12939 |doi=10.1111/pim.12939 |issn=0141-9838 |pmc=9542036 |pmid=35712983}}

Chronic helminthiasis may cause severe morbidity.{{Cite book |title=Medical Microbiology |vauthors=Baron S |publisher=Galveston (TX): The University of Texas Medical Branch at Galveston |year=1996 |isbn=978-0963117212 |edition=4 |chapter=87 (Helminths: Pathogenesis and Defenses by Wakelin D |pmid=21413312 |chapter-url=https://www.ncbi.nlm.nih.gov/books/NBK8191/}} Helminthiasis has been found to result in poor birth outcome, poor cognitive development, poor school and work performance, decreased productivity, poor socioeconomic development, and poverty.

Helminthiasis may cause chronic illness through malnutrition including vitamin deficiencies, stunted growth, anemia, and protein-energy malnutrition. Worms compete directly with their hosts for nutrients, but the magnitude of this effect is likely minimal as the nutritional requirements of worms is relatively small. In pigs and humans, Ascaris has been linked to lactose intolerance and vitamin A, amino acid, and fat malabsorption. Impaired nutrient uptake may result from direct damage to the intestinal mucosal wall or from more subtle changes such as chemical imbalances and changes in gut flora.Crompton, D. W. T. (1993). [https://books.google.com/books?id=oT6BrfK7XQYC&dq=crompton%20Human%20Nutrition%20and%20Parasitic%20Infection.&pg=PA5202 Human Nutrition and Parasitic Infection]. Cambridge University Press. Alternatively, the worms’ release of protease inhibitors to defend against the body's digestive processes may impair the breakdown of other nutrients.{{Cite book |url=http://pdf.usaid.gov/pdf_docs/PNABQ180.pdf |archive-url=https://web.archive.org/web/20110718111936/http://pdf.usaid.gov/pdf_docs/PNABQ180.pdf |url-status=dead |archive-date=July 18, 2011 |title=Nutrition, Health, and Learning: Current Issues and Trends |vauthors=Levinger B |date=1992 |series=School Nutrition and Health Network Monograph Series, #1. |quote=Please note that this estimate is less current than the Watkins and Pollitt estimate, leading Levinger to underestimate the number infected.}}{{Cite journal |vauthors=Watkins WE, Pollitt E |date=March 1997 |title="Stupidity or worms": do intestinal worms impair mental performance? |journal=Psychological Bulletin |volume=121 |issue=2 |pages=171–91 |doi=10.1037/0033-2909.121.2.171 |pmid=9100486}} In addition, worm induced diarrhoea may shorten gut transit time, thus reducing absorption of nutrients.

Malnutrition due to worms can give rise to anorexia.{{Cite web |last=The World Bank |title=World Development Report 1993: Investing in Health |url=http://files.dcp2.org/pdf/WorldDevelopmentReport1993.pdf |url-status=dead |archive-url=https://web.archive.org/web/20140225050318/http://files.dcp2.org/pdf/WorldDevelopmentReport1993.pdf |archive-date=2014-02-25 |access-date=2014-10-21}} A study of 459 children in Zanzibar revealed spontaneous increases in appetite after deworming.{{Cite journal |name-list-style=vanc |vauthors=Stoltzfus RJ, Chway HM, Montresor A, Tielsch JM, Jape JK, Albonico M, Savioli L |date=February 2004 |title=Low dose daily iron supplementation improves iron status and appetite but not anemia, whereas quarterly anthelminthic treatment improves growth, appetite and anemia in Zanzibari preschool children |journal=The Journal of Nutrition |volume=134 |issue=2 |pages=348–56 |doi=10.1093/jn/134.2.348 |pmid=14747671 |doi-access=free}} Anorexia might be a result of the body's immune response and the stress of combating infection. Specifically, some of the cytokines released in the immune response to worm infestation have been linked to anorexia in animals.

Helminths may cause iron-deficiency anemia. This is most severe in heavy hookworm infections, as Necator americanus and Ancylostoma duodenale feed directly on the blood of their hosts. Although the daily consumption of an individual worm (0.02–0.07 ml and 0.14–0.26 ml respectively) is small, the collective consumption under heavy infection can be clinically significant. Intestinal whipworm may also cause anemia. Anemia has also been associated with reduced stamina for physical labor, a decline in the ability to learn new information, and apathy, irritability, and fatigue. A study of the effect of deworming and iron supplementation in 47 students from the Democratic Republic of the Congo found that the intervention improved cognitive function.{{Cite journal |vauthors=Boivin MJ, Giordani B |date=April 1993 |title=Improvements in cognitive performance for schoolchildren in Zaire, Africa, following an iron supplement and treatment for intestinal parasites |url=http://jpepsy.oxfordjournals.org/cgi/reprint/18/2/249 |journal=Journal of Pediatric Psychology |volume=18 |issue=2 |pages=249–64 |doi=10.1093/jpepsy/18.2.249 |pmid=8492277 |id=2|url-access=subscription }} Another study found that in 159 Jamaican schoolchildren, deworming led to better auditory short-term memory and scanning and retrieval of long-term memory over a period of nine-weeks.{{Cite journal |vauthors=Nokes C, Grantham-McGregor SM, Sawyer AW, Cooper ES, Bundy DA |date=February 1992 |title=Parasitic helminth infection and cognitive function in school children |journal=Proceedings. Biological Sciences |volume=247 |issue=1319 |pages=77–81 |bibcode=1992RSPSB.247...77N |doi=10.1098/rspb.1992.0011 |pmid=1349184 |s2cid=22199934}}

Malnutrition due to helminths may affect cognitive function leading to low educational performance, decreased concentration and difficulty with abstract cognitive tasks. Iron deficiency in infants and preschoolers is associated with "lower scores ... on tests of mental and motor development ... [as well as] increased fearfulness, inattentiveness, and decreased social responsiveness". Studies in the Philippines and Indonesia found a significant correlation between helminthiasis and decreased memory and fluency.{{Cite journal |display-authors=6 |name-list-style=vanc |vauthors=Ezeamama AE, Friedman JF, Acosta LP, Bellinger DC, Langdon GC, Manalo DL, Olveda RM, Kurtis JD, McGarvey ST |date=May 2005 |title=Helminth infection and cognitive impairment among Filipino children |journal=The American Journal of Tropical Medicine and Hygiene |volume=72 |issue=5 |pages=540–548 |doi=10.4269/ajtmh.2005.72.540 |pmc=1382476 |pmid=15891127}}{{Cite journal |vauthors=Sakti H, Nokes C, Hertanto WS, Hendratno S, Hall A, Bundy DA |date=May 1999 |title=Evidence for an association between hookworm infection and cognitive function in Indonesian school children |url=http://www3.interscience.wiley.com/cgi-bin/fulltext/119090322/PDFSTART |journal=Tropical Medicine & International Health |volume=4 |issue=5 |pages=322–34 |doi=10.1046/j.1365-3156.1999.00410.x |pmid=10402967 |s2cid=16553760|doi-access=free }}{{dead link|date=February 2019|bot=medic}}{{cbignore|bot=medic}} Large parasite burdens, particularly severe hookworm infections, are also associated with absenteeism, under-enrollment, and attrition in school children.

Helminths are transmitted to the final host in several ways. The most common infection is through ingestion of contaminated vegetables, drinking water, and raw or undercooked meat. Contaminated food may contain eggs of nematodes such as Ascaris, Enterobius, and Trichuris; cestodes such as Taenia, Hymenolepis, and Echinococcus; and trematodes such as Fasciola. Raw or undercooked meats are the major sources of Taenia (pork, beef and venison), Trichinella (pork and bear), Diphyllobothrium (fish), Clonorchis (fish), and Paragonimus (crustaceans). Schistosomes and nematodes such as hookworms (Ancylostoma and Necator) and Strongyloides can penetrate the skin directly.

The roundworm, Dracunculus has a complex mode of transmission: it is acquired from drinking infested water or eating frogs and fish that contain (had eaten) infected crustaceans (copepods); and can also be transmitted from infected pets (cats and dogs).{{cite journal | vauthors = Galán-Puchades MT | title = Dracunculiasis: water-borne anthroponosis vs. food-borne zoonosis | journal = Journal of Helminthology | volume = 94 | pages = e76 | date = August 2019 | pmid = 31434586 | doi = 10.1017/S0022149X19000713 | s2cid = 201274949 | hdl = 10550/104649 | hdl-access = free }} Roundworms such as Brugia, Wuchereria and Onchocerca are directly transmitted by mosquitoes.{{cite journal | vauthors = Pilotte N, Unnasch TR, Williams SA | title = The Current Status of Molecular Xenomonitoring for Lymphatic Filariasis and Onchocerciasis | journal = Trends in Parasitology | volume = 33 | issue = 10 | pages = 788–798 | date = October 2017 | pmid = 28756911 | doi = 10.1016/j.pt.2017.06.008 }}{{cite journal | vauthors = Nanduri J, Kazura JW | title = Clinical and laboratory aspects of filariasis | journal = Clinical Microbiology Reviews | volume = 2 | issue = 1 | pages = 39–50 | date = January 1989 | pmid = 2644023 | pmc = 358099 | doi = 10.1128/CMR.2.1.39 }} In the developing world, the use of contaminated water is a major risk factor for infection.{{Cite web |year=2009 |title=Contaminated drinking water |url=http://www.charitywater.org/whywater |website=Charity Water |vauthors=Harrison S, Deng A, Green B, Gorder C, Goodman MZ}}{{verify source|date=July 2022|reason=Did not find article}} Infection can also take place through the practice of geophagy, which is not uncommon in parts of sub-Saharan Africa. Soil is eaten, for example, by children or pregnant women to counteract a real or perceived deficiency of minerals in their diet.{{Cite journal |vauthors=Bisi-Johnson MA, Obi CL, Ekosse GE |date=2010 |title=Microbiological and health related perspectives of geophagia: an overview |url=http://www.ajol.info/index.php/ajb/article/download/92778/82208 |journal=African Journal of Biotechnology |volume=9 |issue=36 |pages=5784–91}}

File:Identification and quantification of helminth eggs.png

Specific helminths can be identified through microscopic examination of their eggs (ova) found in faecal samples. The number of eggs is measured in units of eggs per gram. However, it does not quantify mixed infections, and in practice, is inaccurate for quantifying the eggs of schistosomes and soil-transmitted helminths.{{Cite journal |vauthors=Krauth SJ, Coulibaly JT, Knopp S, Traoré M, N'Goran EK, Utzinger J |year=2012 |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 |doi=10.1371/journal.pntd.0001969 |pmc=3527364 |pmid=23285307 |doi-access=free }} Sophisticated tests such as serological assays, antigen tests, and molecular diagnosis are also available; however, they are time-consuming, expensive and not always reliable.{{Cite journal |vauthors=Hunt PW, Lello J |date=May 2012 |title=How to make DNA count: DNA-based diagnostic tools in veterinary parasitology |journal=Veterinary Parasitology |volume=186 |issue=1–2 |pages=101–8 |doi=10.1016/j.vetpar.2011.11.055 |pmid=22169224}}

Disrupting the cycle of the worm will prevent infestation and re-infestation. Prevention of infection can largely be achieved by addressing the issues of WASH—water, sanitation and hygiene.{{Cite web |title=Water, Sanitation & Hygiene: Strategy Overview |url=http://www.gatesfoundation.org/What-We-Do/Global-Development/Water-Sanitation-and-Hygiene |url-status=dead |archive-url=https://web.archive.org/web/20171107060749/http://www.gatesfoundation.org/What-We-Do/Global-Development/Water-Sanitation-and-Hygiene |archive-date=7 November 2017 |access-date=27 April 2015 |website=Bill & Melinda Gates Foundation}}{{Cite web |title=Water, Sanitation, and Hygiene: Introduction |url=http://www.unicef.org/wash/index_3951.html |url-status=dead |archive-url=https://web.archive.org/web/20150424221052/http://www.unicef.org/wash/index_3951.html |archive-date=24 April 2015 |access-date=27 April 2015 |website=UNICEF }}{{Cite web |title=Goal 7: Ensure Environmental Sustainability |url=https://www.un.org/millenniumgoals/environ.shtml |access-date=27 April 2015 |website=United Nations Millennium Development Goals website}} The reduction of open defecation is particularly called for,{{Cite journal |vauthors=Ziegelbauer K, Speich B, Mäusezahl D, Bos R, Keiser J, Utzinger J |date=January 2012 |title=Effect of sanitation on soil-transmitted helminth infection: systematic review and meta-analysis |journal=PLOS Medicine |volume=9 |issue=1 |pages=e1001162 |doi=10.1371/journal.pmed.1001162 |pmc=3265535 |pmid=22291577 |doi-access=free }}{{Cite journal |vauthors=Strunz EC, Addiss DG, Stocks ME, Ogden S, Utzinger J, Freeman MC |date=March 2014 |title=Water, sanitation, hygiene, and soil-transmitted helminth infection: a systematic review and meta-analysis |journal=PLOS Medicine |volume=11 |issue=3 |pages=e1001620 |doi=10.1371/journal.pmed.1001620 |pmc=3965411 |pmid=24667810 |doi-access=free }} as is stopping the use of human waste as fertilizer.

Further preventive measures include adherence to appropriate food hygiene, wearing of shoes, regular deworming of pets, and the proper disposal of their feces.

Scientists are also searching for a vaccine against helminths, such as a hookworm vaccine.{{Cite journal |display-authors=6 |vauthors=Hotez PJ, Diemert D, Bacon KM, Beaumier C, Bethony JM, Bottazzi ME, Brooker S, Couto AR, Freire M, Homma A, Lee BY, Loukas A, Loblack M, Morel CM, Oliveira RC, Russell PK |date=April 2013 |title=The Human Hookworm Vaccine |journal=Vaccine |volume=31 |issue=Suppl 2 |pages=B227-32 |doi=10.1016/j.vaccine.2012.11.034 |pmc=3988917 |pmid=23598487}}

{{Main|Anthelmintic}}

Broad-spectrum benzimidazoles (such as albendazole and mebendazole) are the first line treatment of intestinal roundworm and tapeworm infections. Macrocyclic lactones (such as ivermectin) are effective against adult and migrating larval stages of nematodes. Praziquantel is the drug of choice for schistosomiasis, taeniasis, and most types of food-borne trematodiases. Oxamniquine is also widely used in mass deworming programmes. Pyrantel is commonly used for veterinary nematodiasis.{{Cite web |title=Anthelmintics |url=https://www.drugs.com/drug-class/anthelmintics.html |access-date=17 November 2014 |website=Drugs.com}}{{Cite web |title=Overview of Anthelmintics |url=http://www.merckmanuals.com/vet/pharmacology/anthelmintics/overview_of_anthelmintics.html |access-date=17 November 2014 |website=The Merck Veterinary Manual |publisher=Merck Sharp & Dohme Corp.}} Artemisinins and derivatives are proving to be candidates as drugs of choice for trematodiasis.{{Cite journal |vauthors=Pérez del Villar L, Burguillo FJ, López-Abán J, Muro A |date=2012 |title=Systematic review and meta-analysis of artemisinin based therapies for the treatment and prevention of schistosomiasis |journal=PLOS ONE |volume=7 |issue=9 |pages=e45867 |bibcode=2012PLoSO...745867P |doi=10.1371/journal.pone.0045867 |pmc=3448694 |pmid=23029285 |doi-access=free}}

{{Main|Mass deworming}}

In regions where helminthiasis is common, mass deworming treatments may be performed, particularly among school-age children, who are a high-risk group.{{Cite book |last=WHO |url=http://whqlibdoc.who.int/publications/2006/9241547103_eng.pdf |title=Preventive chemotherapy in human helminthiasis: coordinated use of anthelminthic drugs in control interventions: a manual for health professionals and programme managers |publisher=WHO Press, World Health Organization, Geneva, Switzerland |year=2006 |isbn=978-9241547109 |pages=1–61}}{{Cite journal |display-authors=6 |vauthors=Prichard RK, Basáñez MG, Boatin BA, McCarthy JS, García HH, Yang GJ, Sripa B, Lustigman S |year=2012 |title=A research agenda for helminth diseases of humans: intervention for control and elimination |journal=PLOS Neglected Tropical Diseases |volume=6 |issue=4 |pages=e1549 |doi=10.1371/journal.pntd.0001549 |pmc=3335868 |pmid=22545163 |doi-access=free }} Most of these initiatives are undertaken by the World Health Organization (WHO) with positive outcomes in many regions.{{Cite journal |vauthors=Bundy DA, Walson JL, Watkins KL |date=March 2013 |title=Worms, wisdom, and wealth: why deworming can make economic sense |journal=Trends in Parasitology |volume=29 |issue=3 |pages=142–8 |doi=10.1016/j.pt.2012.12.003 |pmid=23332661}}{{Cite journal |vauthors=Albonico M, Allen H, Chitsulo L, Engels D, Gabrielli AF, Savioli L |date=March 2008 |title=Controlling soil-transmitted helminthiasis in pre-school-age children through preventive chemotherapy |journal=PLOS Neglected Tropical Diseases |volume=2 |issue=3 |pages=e126 |doi=10.1371/journal.pntd.0000126 |pmc=2274864 |pmid=18365031 |doi-access=free }} Deworming programs can improve school attendance by 25 percent.{{Cite journal |vauthors=Miguel E, Kremer M |year=2004 |title=Worms: Identifying Impacts on Education and Health in the Presence of Treatment Externalities |journal=Econometrica |volume=72 |issue=1 |pages=159–217 |citeseerx=10.1.1.336.7123 |doi=10.1111/j.1468-0262.2004.00481.x}} Although deworming improves the health of an individual, outcomes from mass deworming campaigns, such as reduced deaths or increases in cognitive ability, nutritional benefits, physical growth, and performance, are uncertain or not apparent.{{Cite web |date=2015-08-04 |title=Economist, World Bank |url=http://blogs.worldbank.org/impactevaluations/worm-wars-anthology |access-date=5 August 2015 |website=Development Impact blog, World Bank |publisher=World Bank |vauthors=Evans D}}{{Cite journal |vauthors=Hawkes N |date=January 2012 |title=Deworming debunked |journal=BMJ |volume=346 |issue=jan02 1 |pages=e8558 |doi=10.1136/bmj.e8558 |pmid=23284157 |s2cid=5568263|doi-access=free }}{{Cite journal |vauthors=Taylor-Robinson DC, Maayan N, Donegan S, Chaplin M, Garner P |date=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 |pmc=6737502 |pmid=31508807}}{{Cite journal |vauthors=Ahuja A, Baird S, Hicks JH, Kremer M, Miguel E, Powers S |date=2015 |title=When Should Governments Subsidize Health? The Case of Mass Deworming |journal=The World Bank Economic Review |volume=29 |issue=suppl 1 |pages=S9–S24 |doi=10.1093/wber/lhv008 |doi-access=free}}

File:Ascaris infection- Difficult intestinal anastamosis - joining up of two ends- clearly if we cut out a section of bowel we're left with two ends that need to be joined up (South Africa) (15806559973).jpg (ascaris infection) - Difficult surgical procedure in South Africa on a gangrenous piece of bowel that had to be cut out; live ascaris worms are emerging.]]

File:Piece of intestine, blocked by worms (16424898321).jpg

If complications of helminthiasis, such as intestinal obstruction occur, emergency surgery may be required. Patients who require non-emergency surgery, for instance for removal of worms from the biliary tree, can be pre-treated with the anthelmintic drug albendazole.

Areas with the highest prevalence of helminthiasis are tropical and subtropical areas including sub-Saharan Africa, central and east Asia, and the Americas.{{citation needed|date=January 2021}}

Some types of helminthiases are classified as neglected tropical diseases.{{Cite web |title=Fact sheets: neglected tropical diseases |url=https://www.who.int/topics/tropical_diseases/factsheets/neglected/en |url-status=dead |archive-url=https://web.archive.org/web/20110124092537/http://www.who.int/topics/tropical_diseases/factsheets/neglected/en/ |archive-date=January 24, 2011 |access-date=6 December 2014 |website=World Health Organization |publisher=WHO Media Centre}} They include:

• Soil-transmitted helminthiases
• Roundworm infections such as lymphatic filariasis, dracunculiasis, and onchocerciasis
• Trematode infections, such as schistosomiasis, and food-borne trematodiases, including fascioliasis, clonorchiasis, opisthorchiasis, and paragonimiasis
• Tapeworm infections such as cysticercosis, taeniasis, and echinococcosis

The soil-transmitted helminths (A. lumbricoides, T. trichiura, N. americanus, A. duodenale), schistosomes, and filarial worms collectively infect more than a quarter of the human population worldwide at any one time, far surpassing HIV and malaria together.{{Cite book |url=https://books.google.com/books?id=M6qOL15UlesC |title=Handbook of Helminthiasis for Public Health |vauthors=Crompton DW, Savioli L |publisher=CRC Press, Boca Raton, Florida, US |year=2007 |isbn=9781420004946 |pages=1–362}}{{Cite journal |vauthors=Lustigman S, Prichard RK, Gazzinelli A, Grant WN, Boatin BA, McCarthy JS, Basáñez MG |year=2012 |title=A research agenda for helminth diseases of humans: the problem of helminthiases |journal=PLOS Neglected Tropical Diseases |volume=6 |issue=4 |pages=e1582 |doi=10.1371/journal.pntd.0001582 |pmc=3335854 |pmid=22545164 |doi-access=free }} Schistosomiasis is the second most prevalent parasitic disease of humans after malaria.{{Cite book |last=WHO |title=Schistosomiasis: progress report 2001 - 2011, strategic plan 2012 - 2020 |publisher=WHO Press, World Health Organization, Geneva, Switzerland |year=2013 |isbn=9789241503174 |pages=1–270 |hdl=10665/78074?mode=full}}

In 2014–15, the WHO estimated that approximately 2 billion people were infected with soil-transmitted helminthiases, 249 million with schistosomiasis,{{Cite web |date=May 2015 |title=Malaria |url=https://www.who.int/mediacentre/factsheets/fs094/en |url-status=dead |archive-url=https://web.archive.org/web/20040614022014/http://www.who.int/mediacentre/factsheets/fs094/en/ |archive-date=June 14, 2004 |access-date=7 February 2016 |website=Fact sheet N°94 |publisher=WHO Media Centre}} 56 million people with food-borne trematodiasis,{{Cite web |date=2014 |title=Foodborne trematode infections |url=https://www.who.int/foodborne_trematode_infections/en |access-date=7 February 2016 |website=Factsheet N°368 |publisher=WHO Media Centre}} 120 million with lymphatic filariasis,{{Cite web |date=May 2015 |title=Lymphatic filariasis |url=https://www.who.int/mediacentre/factsheets/fs102/en |url-status=dead |archive-url=https://web.archive.org/web/20040502123722/http://www.who.int/mediacentre/factsheets/fs102/en/ |archive-date=May 2, 2004 |access-date=7 February 2016 |website=Fact sheet N°102 |publisher=WHO Media centre}} 37 million people with onchocerciasis,{{Cite web |date=March 2014 |title=A global brief on vector-borne diseases |url=http://apps.who.int/iris/bitstream/10665/111008/1/WHO_DCO_WHD_2014.1_eng.pdf?ua=1 |access-date=8 March 2016 |publisher=World Health Organization |page=22}} and 1 million people with echinococcosis.{{Cite web |date=May 2015 |title=Echinococcosis |url=https://www.who.int/mediacentre/factsheets/fs377/en |url-status=dead |archive-url=https://web.archive.org/web/20140221184309/http://www.who.int/mediacentre/factsheets/fs377/en/ |archive-date=February 21, 2014 |access-date=7 February 2016 |website=Fact sheet N°377 |publisher=WHO Media Centre}} Another source estimated a much higher figure of 3.5 billion infected with one or more soil-transmitted helminths.{{Cite journal |vauthors=Ojha SC, Jaide C, Jinawath N, Rotjanapan P, Baral P |date=January 2014 |title=Geohelminths: public health significance |url=http://jidc.org/index.php/journal/article/download/24423707/975 |journal=Journal of Infection in Developing Countries |volume=8 |issue=1 |pages=5–16 |doi=10.3855/jidc.3183 |pmid=24423707 |doi-access=free}}Velleman, Y., Pugh, I. (2013). [http://www.susana.org/en/resources/library/details/1794 Under-nutrition and water, sanitation and hygiene - Water, sanitation and hygiene (WASH) play a fundamental role in improving nutritional outcomes. A successful global effort to tackle under-nutrition must include WASH]. WaterAid and Share, UK

In 2014, only 148 people were reported to have dracunculiasis because of a successful eradication campaign for that particular helminth, which is easier to eradicate than other helminths as it is transmitted only by drinking contaminated water.{{Cite web |date=March 2014 |title=Dracunculiasis (guinea-worm disease) |url=https://www.who.int/mediacentre/factsheets/fs359/en |url-status=dead |archive-url=https://web.archive.org/web/20130730230030/http://www.who.int/mediacentre/factsheets/fs359/en/ |archive-date=July 30, 2013 |access-date=6 December 2014 |website=Fact sheet N°359 (Revised) |publisher=WHO Media Centre}}

Because of their high mobility and lower standards of hygiene, school-age children are particularly vulnerable to helminthiasis.{{Cite book |url=https://www.who.int/wormcontrol/documents/en/001to011.pdf |title=Helminth Control in School-Age Children: A Guide for Managers of Control Programs |vauthors=Montresor A, Crompton W, ((World Health Organization)), Gyorkos TW, Savioli L |publisher=World Health Organization |year=2002 |isbn=9789241545563 |archive-url=https://web.archive.org/web/20040718002440/https://www.who.int/wormcontrol/documents/en/001to011.pdf |archive-date=18 July 2004}} Most children from developing nations will have at least one infestation. Multi-species infections are very common.{{Cite journal |vauthors=Bethony J, Brooker S, Albonico M, Geiger SM, Loukas A, Diemert D, Hotez PJ |date=May 2006 |title=Soil-transmitted helminth infections: ascariasis, trichuriasis, and hookworm |journal=Lancet |volume=367 |issue=9521 |pages=1521–32 |doi=10.1016/S0140-6736(06)68653-4 |pmid=16679166 |s2cid=8425278}}

The most common intestinal parasites in the United States are Enterobius vermicularis, Giardia lamblia, Ancylostoma duodenale, Necator americanus, and Entamoeba histolytica.{{Cite journal |vauthors=Kucik CJ, Martin GL, Sortor BV |date=March 2004 |title=Common intestinal parasites |url=https://pubmed.ncbi.nlm.nih.gov/15023017 |journal=American Family Physician |volume=69 |issue=5 |pages=1161–8 |pmid=15023017}}

In a developing country like Bangladesh, the most common species are round worm (Ascaris lumbricoides), whipworm (Tricurias tricuras) and hookworm

(Ancylostoma duodenalis).[https://www.ajol.info/index.php/sajchh/article/view/73423]

Even in areas of high prevalence, the frequency and severity of infection is not uniform within communities or families.{{Cite book |title=Hunter's tropical medicine and emerging infectious diseases |vauthors=Magill AJ, Hill DR, Solomon T, Ryan ET |date=2013 |publisher=Saunders |isbn=978-1-4160-4390-4 |edition=9th |location=New York |page=804}} A small proportion of community members harbour the majority of worms, and this depends on age. The maximum worm burden is at five to ten years of age, declining rapidly thereafter.{{Cite book |title=Hunter's tropical medicine and emerging infectious diseases |vauthors=Magill A |date=2013 |publisher=Saunders |isbn=978-1-4160-4390-4 |edition=9th |location=New York |page=804}} Individual predisposition to helminthiasis for people with the same sanitation infrastructure and hygiene behavior is thought to result from differing immunocompetence, nutritional status, and genetic factors. Because individuals are predisposed to a high or a low worm burden, the burden reacquired after successful treatment is proportional to that before treatment.

It is estimated that intestinal nematode infections cause 5 million disability-adjusted life years (DALYS) to be lost, of which hookworm infections account for more than 3 million DALYS and ascaris infections more than 1 million.{{cite journal | vauthors = Hotez PJ, Alvarado M, Basáñez MG, Bolliger I, Bourne R, Boussinesq M, Brooker SJ, Brown AS, Buckle G, Budke CM, Carabin H, Coffeng LE, Fèvre EM, Fürst T, Halasa YA, Jasrasaria R, Johns NE, Keiser J, King CH, Lozano R, Murdoch ME, O'Hanlon S, Pion SD, Pullan RL, Ramaiah KD, Roberts T, Shepard DS, Smith JL, Stolk WA, Undurraga EA, Utzinger J, Wang M, Murray CJ, Naghavi M | display-authors = 6 | title = The global burden of disease study 2010: interpretation and implications for the neglected tropical diseases | journal = PLOS Neglected Tropical Diseases | volume = 8 | issue = 7 | pages = e2865 | date = July 2014 | pmid = 25058013 | pmc = 4109880 | doi = 10.1371/journal.pntd.0002865 | doi-access = free }} There are also signs of progress: The Global Burden of Disease Study published in 2015 estimates a 46 percent (59 percent when age standardised) reduction in years lived with disability (YLD) for the 13-year time period from 1990 to 2013 for all intestinal/nematode infections, and even a 74 percent (80 percent when age standardised) reduction in YLD from ascariasis.{{cite journal | title = Global, regional, and national incidence, prevalence, and years lived with disability for 301 acute and chronic diseases and injuries in 188 countries, 1990-2013: a systematic analysis for the Global Burden of Disease Study 2013 | journal = Lancet | volume = 386 | issue = 9995 | pages = 743–800 | date = August 2015 | pmid = 26063472 | pmc = 4561509 | doi = 10.1016/S0140-6736(15)60692-4 | last1 = Vos | first1 = Theo | last2 = Barber | first2 = Ryan M. | last3 = Bell | first3 = Brad | last4 = Bertozzi-Villa | first4 = Amelia | last5 = Biryukov | first5 = Stan | last6 = Bolliger | first6 = Ian | last7 = Charlson | first7 = Fiona | last8 = Davis | first8 = Adrian | last9 = Degenhardt | first9 = Louisa | last10 = Dicker | first10 = Daniel | last11 = Duan | first11 = Leilei | last12 = Erskine | first12 = Holly | last13 = Feigin | first13 = Valery L. | last14 = Ferrari | first14 = Alize J. | last15 = Fitzmaurice | first15 = Christina | last16 = Fleming | first16 = Thomas | last17 = Graetz | first17 = Nicholas | last18 = Guinovart | first18 = Caterina | last19 = Haagsma | first19 = Juanita | last20 = Hansen | first20 = Gillian M. | last21 = Hanson | first21 = Sarah Wulf | last22 = Heuton | first22 = Kyle R. | last23 = Higashi | first23 = Hideki | last24 = Kassebaum | first24 = Nicholas | last25 = Kyu | first25 = Hmwe | last26 = Laurie | first26 = Evan | last27 = Liang | first27 = Xiofeng | last28 = Lofgren | first28 = Katherine | last29 = Lozano | first29 = Rafael | last30 = MacIntyre | first30 = Michael F. | display-authors = 1 }}

As many as 135,000 die annually from soil transmitted helminthiasis.{{Cite journal |vauthors=Yap P, Fürst T, Müller I, Kriemler S, Utzinger J, Steinmann P |date=August 2012 |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 |doi=10.3791/3966 |pmc=3486755 |pmid=22951972}}

The 1990–2013 Global Burden of Disease Study estimated 5,500 direct deaths from schistosomiasis,{{Cite journal | vauthors = Naghavi M, Wang H, Lozano R, Davis A, Liang X, Zhou M, etal |date=January 2015 |title=Global, regional, and national age-sex specific all-cause and cause-specific mortality for 240 causes of death, 1990-2013: a systematic analysis for the Global Burden of Disease Study 2013 |journal=Lancet |volume=385 |issue=9963 |pages=117–171 |doi=10.1016/S0140-6736(14)61682-2 |pmc=4340604 |pmid=25530442 |hdl=11655/15525 |collaboration=GBD 2013 Mortality Causes of Death Collaborators}} while more than 200,000 people were estimated in 2013 to die annually from causes related to schistosomiasis.{{Cite journal |vauthors=Thétiot-Laurent SA, Boissier J, Robert A, Meunier B |date=July 2013 |title=Schistosomiasis chemotherapy |journal=Angewandte Chemie |volume=52 |issue=31 |pages=7936–56 |doi=10.1002/anie.201208390 |pmid=23813602}} Another 20 million have severe consequences from the disease.{{Cite journal |vauthors=Kheir MM, Eltoum IA, Saad AM, Ali MM, Baraka OZ, Homeida MM |date=February 1999 |title=Mortality due to schistosomiasis mansoni: a field study in Sudan |journal=The American Journal of Tropical Medicine and Hygiene |volume=60 |issue=2 |pages=307–10 |doi=10.4269/ajtmh.1999.60.307 |pmid=10072156 |doi-access=free}} It is the most deadly of the neglected tropical diseases.{{Cite web |date=6 June 2011 |title=Neglected Tropical Diseases |url=https://www.cdc.gov/globalhealth/ntd/diseases/schisto_burden.html |access-date=28 November 2014 |website=cdc.gov}}

• Kato technique

{{Reflist}}

{{Medical resources

| ICD10 = {{ICD10|B|83|9|b|65}}

| ICD9 = {{ICD9|128.9}}

| ICDO =

| OMIM =

| DiseasesDB = 28826

| MedlinePlus =

| eMedicineSubj =

| eMedicineTopic =

| MeshID = D006373

}}

• [https://www.who.int/topics/helminthiasis/en/ Information at WHO]
• [http://ec.europa.eu/research/health/infectious-diseases/neglected-diseases/helminth_en.html European Commission]
• [https://www.cdc.gov/parasites/sth/ Center for Disease Control and Prevention]
• [http://www.thiswormyworld.org/ Global Atlas of Helminth Infections] {{Webarchive|url=https://web.archive.org/web/20151108015800/http://www.thiswormyworld.org/ |date=2015-11-08 }}

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