Pinworm (parasite)

Last updated

Pinworm
Evermicularis SC posterior.jpg
Pinworms (U.S.)/Threadworms (U.K.) (Enterobius vermicularis)
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Animalia
Phylum: Nematoda
Class: Chromadorea
Order: Rhabditida
Family: Oxyuridae
Genus: Enterobius
Baird, 1853
Species

The pinworm (species Enterobius vermicularis), also known as threadworm (in the United Kingdom, Australia and New Zealand) or seatworm, is a parasitic worm. It is a nematode (roundworm) and a common intestinal parasite or helminth, especially in humans. [7] The medical condition associated with pinworm infestation is known as pinworm infection (enterobiasis) [8] (a type of helminthiasis) or less precisely as oxyuriasis in reference to the family Oxyuridae. [9]

Contents

Other than human, Enterobius vermicularis were reported from bonnet macaque. [10] Other species seen in primates include Enterobius buckleyi in Orangutan [11] and Enterobius anthropopitheci in chimpanzee. Enterobius vermicularis is common in human children and transmitted via the faecal-oral route. Humans are the only natural host of Enterobius vermicularis. [12] Enterobius gregorii, another human species is morphologically indistinguishable from Enterobius vermicularis except the spicule size. [13] Throughout this article, the word "pinworm" refers to Enterobius. In British usage, however, pinworm refers to Strongyloides , while Enterobius is called threadworm. [14]

Classification

The pinworm (genus Enterobius) is a type of roundworm (nematode), and three species of pinworm have been identified with certainty. [15] Humans are hosts only to Enterobius vermicularis (formerly Oxyurias vermicularis). [16] Chimpanzees are host to Enterobius anthropopitheci, which is morphologically distinguishable from the human pinworm. [5] Hugot (1983) claims another species affects humans, Enterobius gregorii, which is supposedly a sister species of E. vermicularis, and has a slightly smaller spicule (i.e., sexual organ). [17] Its existence is controversial, however; Totkova et al. (2003) consider the evidence to be insufficient, [6] and Hasegawa et al. (2006) contend that E. gregorii is a younger stage of E. vermicularis. [4] [5] Regardless of its status as a distinct species, E. gregorii is considered clinically identical to E. vermicularis. [16]

Morphology

Two female pinworms next to a ruler: The markings are 1 mm apart. Threadworm.jpg
Two female pinworms next to a ruler: The markings are 1 mm apart.

The adult female has a sharply pointed posterior end, is 8 to 13 mm long, and 0.5 mm thick. [18] The adult male is considerably smaller, measuring 2 to 5 mm long and 0.2 mm thick, and has a curved posterior end. [18] The eggs are translucent [18] and have a surface that adheres to objects. [19] The eggs measure 50 to 60 μm by 20 to 30 μm, and have a thick shell flattened on one side. [18] The small size and colourlessness of the eggs make them invisible to the naked eye, except in barely visible clumps of thousands of eggs. Eggs may contain a developing embryo or a fully developed pinworm larva. [18] The larvae grow to 140–150 μm in length. [19]

Life cycle

Life cycle of E. vermicularis showing the stages inside and outside of the human body Enterobius vermicularis life cycle.tif
Life cycle of E. vermicularis showing the stages inside and outside of the human body

The entire life cycle, from egg to adult, takes place in the human gastrointestinal tract of a single host, [18] [19] from about 2–4 weeks [20] or about 4–8 weeks. [21] E. vermicularis molts four times; the first two within the egg before hatching and two before becoming an adult worm. [22]

Although infection often occurs via ingestion of embryonated eggs by inadequate hand washing or nail biting, inhalation followed by swallowing of airborne eggs may occur rarely. [19] [21] The eggs hatch in the duodenum (i.e., first part of the small intestine). [23] The emerging pinworm larvae grow rapidly to a size of 140 to 150 μm, [20] and migrate through the small intestine towards the colon. [19] During this migration, they moult twice and become adults. [19] [21] Females survive for 5 to 13 weeks, and males about 7 weeks. [19] The male and female pinworms mate in the ileum (i.e., last part of the small intestine), [19] whereafter the male pinworms usually die, [23] and are passed out with stool. [24] The gravid female pinworms settle in the ileum, caecum (i.e., beginning of the large intestine), appendix and ascending colon, [19] where they attach themselves to the mucosa [21] and ingest colonic contents. [25]

Almost the entire body of a gravid female becomes filled with eggs. [23] The estimations of the number of eggs in a gravid female pinworm range from about 11,000 [19] to 16,000. [21] The egg-laying process begins about five weeks after initial ingestion of pinworm eggs by the human host. [19] The gravid female pinworms migrate through the colon towards the rectum at a rate of 12 to 14 cm per hour. [19] They emerge from the anus, and while moving on the skin near the anus, the female pinworms deposit eggs either through (1) contracting and expelling the eggs, (2) dying and then disintegrating, or (3) bodily rupture due to the host scratching the worm. [23] After depositing the eggs, the female becomes opaque and dies. [24] The female emerges from the anus to obtain the oxygen necessary for the maturation of the eggs. [24]

Infection

E. vermicularis causes the medical condition pinworm infection also known as enterobiasis, whose primary symptom is itching in the anal area. [26] Extraintestinal disease is rare and most commonly involves the female reproductive tract, [27] but spleen abscess has also been reported. [28] Enterobius vermicularis infections are found to be correlated with stunting and lower mean I.Q. among prepubescent children. [29] [30]

Distribution

The pinworm has a worldwide distribution, [25] and is the cause of the most common helminthiasis (parasitic worm infection) in the United States, western Europe, and Oceania. [21] In the United States, a study by the Center of Disease Control reported an overall incidence rate of 11.4% among children. [21] Pinworms are particularly common in children, with prevalence rates in this age group having been reported as high as 61% in India, 50% in England, 39% in Thailand, 37% in Sweden, and 29% in Denmark. [21] Finger sucking has been shown to increase both incidence and relapse rates, [21] and nail biting has been similarly associated. [31] Because it spreads from host to host through contamination, pinworms are common among people living in close contact, and tends to occur in all people within a household. [25] The prevalence of pinworms is not associated with gender, [25] nor with any particular social class, race, or culture. [21] Pinworms are an exception to the tenet that intestinal parasites are uncommon in affluent communities. [21]

A fossilized nematode egg was detected in 240 million-year-old fossil dung, [32] showing that parasitic pinworms already infested pre-mammalian cynodonts. The earliest known instance of the pinworms associated with humans is evidenced by pinworm eggs found in human coprolites carbon dated to 7837 BC found in western Utah. [19]

See also

Notes

  1. 1 2 Hasegawa et al. 2005.
  2. 1 2 3 4 5 6 "Enterobius". NCBI taxonomy. Bethesda, MD: National Center for Biotechnology Information. Retrieved 28 February 2019.
  3. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 Registry-Migration.Gbif.Org (2022). "GBIF Backbone Taxonomy". GBIF Secretariat. doi:10.15468/39omei.{{cite journal}}: Cite journal requires |journal= (help)
  4. 1 2 Hasegawa et al. 1998
  5. 1 2 3 Hasegawa et al. 2006
  6. 1 2 Totkova et al. 2003
  7. ↑ Encyclopædia Britannica.
  8. ↑ Merriam-Webster: Enterobiasis
  9. ↑ Merriam-Webster: Oxyuriasis
  10. ↑ C.P., Arjun (October 2015). "A Study of Gastrointestinal Parasites in Bonnet Macaques (Macaca radiata) of Pookode, Wayanad, Kerala". Zoos' Print Journal. Zoo Outreach Organization. Retrieved 20 October 2015.
  11. ↑ Foitová, Ivona; Civáňová, Kristína; Baruš, Vlastimil; Nurcahyo, Wisnu (1 July 2014). "Phylogenetic relationships between pinworms (Nematoda: Enterobiinae) parasitising the critically endangered orang-utan, according to the characterisation of molecular genomic and mitochondrial markers". Parasitology Research. 113 (7): 2455–2466. doi:10.1007/s00436-014-3892-y. ISSN   1432-1955. PMID   24880237. S2CID   15076891.
  12. ↑ Panidis, Stavros; Paramythiotis, Daniel; Panagiotou, Dimitris; Batsis, Georgios; Salonikidis, Spyridon; Kaloutsi, Vassiliki; Michalopoulos, Antonios (1 January 2011). "Acute appendicitis secondary to Enterobius vermicularis infection in a middle-aged man: a case report". Journal of Medical Case Reports. 5: 559. doi: 10.1186/1752-1947-5-559 . ISSN   1752-1947. PMC   3245485 . PMID   22128765.
  13. ↑ CP, Arjun (October 2015). "A Study of Gastrointestinal Parasites in Bonnet Macaque ( Macaca radiata) of Pookode, Wayanad, Kerala" (PDF). Zoos' Print Journal. 10.
  14. ↑ Vanderkooi 2000, p. B-152 & B-225
  15. ↑ NCBI taxonomy database 2009
  16. 1 2 dpdx 2009
  17. ↑ Hugot 1983
  18. 1 2 3 4 5 6 Gutiérrez 2005, p. 354.
  19. 1 2 3 4 5 6 7 8 9 10 11 12 13 Cook 1994, p. 1159
  20. 1 2 Cook et al. 2009, p. 1516
  21. 1 2 3 4 5 6 7 8 9 10 11 Burkhart & burkhart 2005, p. 837
  22. ↑ Rett, Doug. "Enterobius vermicularis". Animal Diversity Web. Retrieved 4 January 2021.
  23. 1 2 3 4 Garcia 1999, p. 246
  24. 1 2 3 Caldwell 1982, p. 307.
  25. 1 2 3 4 Gutiérrez 2005, p. 355.
  26. ↑ "Enterobiasis leads to itching" . Retrieved 20 August 2011.
  27. ↑ Graves, B.; Leder, K.; Sinickas, V.; Sheorey, H. (February 2018). "Extraintestinal Enterobius vermicularis". Pathology. 50: S113–S114. doi:10.1016/j.pathol.2017.12.322.
  28. ↑ Agostinis, Paolo; Cappello, Dario; Riccardi, Niccolò; Michelutti, Teresa; Orsaria, Maria; Zerbato, Verena; Di Bella, Stefano (11 September 2023). Amoroso, Anthony; Nori, Priya; Riedel, David J (eds.). "A 25-Year-Old Woman With Long-Lasting Abdominal Pain and Spleen Abscess". Clinical Infectious Diseases. 77 (5): 795–798. doi:10.1093/cid/ciad047. ISSN   1058-4838. PMID   37696671.
  29. ↑ Guan, M.; Han, B. (2019). "Association between intestinal worm infection and malnutrition among rural children aged 9–11 years old in Guizhou Province, China". BMC Public Health. 19 (1): 1204. doi: 10.1186/s12889-019-7538-y . PMC   6719348 . PMID   31477069.
  30. ↑ Bahader, S. M.; Ali, G. S.; Shaalan, A. H.; Khalil, H. M.; Khalil, N. M. (1995). ""Effects of Enterobius vermicularis infection on intelligence quotient (I.Q) and anthropometric measurements of Egyptian rural children"". Journal of the Egyptian Society of Parasitology. 25 (1): 183–194. PMID   7602161.
  31. ↑ Cook 1994, p. 1160
  32. ↑ Mitrica, Dragos (2 December 2014). "Scientists find 240 million-year-old parasite that infected mammals' ancestor". ZME Science. Retrieved 14 February 2023.

Related Research Articles

<i>Trichuris trichiura</i> Parasitic roundworm that causes intestinal infection

Trichuris trichiura, Trichocephalus trichiuris or whipworm, is a parasitic roundworm that causes trichuriasis when it infects a human large intestine. It is commonly known as the whipworm which refers to the shape of the worm; it looks like a whip with wider "handles" at the posterior end.

<i>Strongyloides stercoralis</i> Species of worm

Strongyloides stercoralis is a human pathogenic parasitic roundworm causing the disease strongyloidiasis. Its common name in the US is threadworm. In the UK and Australia, however, the term threadworm can also refer to nematodes of the genus Enterobius, otherwise known as pinworms.

<i>Necator americanus</i> Species of hookworm

Necator americanus is a species of hookworm commonly known as the New World hookworm. Like other hookworms, it is a member of the phylum Nematoda. It is an obligatory parasitic nematode that lives in the small intestine of human hosts. Necatoriasis—a type of helminthiasis—is the term for the condition of being host to an infestation of a species of Necator. Since N. americanus and Ancylostoma duodenale are the two species of hookworms that most commonly infest humans, they are usually dealt with under the collective heading of "hookworm infection". They differ most obviously in geographical distribution, structure of mouthparts, and relative size.

<i>Taenia solium</i> Species of Cestoda

Taenia solium, the pork tapeworm, belongs to the cyclophyllid cestode family Taeniidae. It is found throughout the world and is most common in countries where pork is eaten. It is a tapeworm that uses humans as its definitive host and pigs as the intermediate or secondary hosts. It is transmitted to pigs through human feces that contain the parasite eggs and contaminate their fodder. Pigs ingest the eggs, which develop into larvae, then into oncospheres, and ultimately into infective tapeworm cysts, called cysticercus. Humans acquire the cysts through consumption of uncooked or under-cooked pork and the cysts grow into an adult worms in the small intestine.

<i>Taenia saginata</i> Species of flatworm

Taenia saginata, commonly known as the beef tapeworm, is a zoonotic tapeworm belonging to the order Cyclophyllidea and genus Taenia. It is an intestinal parasite in humans causing taeniasis and cysticercosis in cattle. Cattle are the intermediate hosts, where larval development occurs, while humans are definitive hosts harbouring the adult worms. It is found globally and most prevalently where cattle are raised and beef is consumed. It is relatively common in Africa, Europe, Southeast Asia, South Asia, and Latin America. Humans are generally infected as a result of eating raw or undercooked beef which contains the infective larvae, called cysticerci. As hermaphrodites, each body segment called proglottid has complete sets of both male and female reproductive systems. Thus, reproduction is by self-fertilisation. From humans, embryonated eggs, called oncospheres, are released with faeces and are transmitted to cattle through contaminated fodder. Oncospheres develop inside muscle, liver, and lungs of cattle into infective cysticerci.

<i>Ascaris suum</i> Species of roundworm

Ascaris suum, also known as the large roundworm of pig, is a parasitic nematode that causes ascariasis in pigs. While roundworms in pigs and humans are today considered as two species with different hosts, cross-infection between humans and pigs is possible; some researchers have thus argued they are the same species. Ascariasis is associated with contact to pigs and pig manure in Denmark.

<span class="mw-page-title-main">Parasitic worm</span> Large type of parasitic organism

Parasitic worms, also known as helminths, are large macroparasites; adults can generally be seen with the naked eye. Many are intestinal worms that are soil-transmitted and infect the gastrointestinal tract. Other parasitic worms such as schistosomes reside in blood vessels.

<span class="mw-page-title-main">Helminthic therapy</span> Deliberate infestation with parasitic worms

Helminthic therapy, an experimental type of immunotherapy, is the treatment of autoimmune diseases and immune disorders by means of deliberate infestation with a helminth or with the eggs of a helminth. Helminths are parasitic worms such as hookworms, whipworms, and threadworms that have evolved to live within a host organism on which they rely for nutrients. These worms are members of two phyla: nematodes, which are primarily used in human helminthic therapy, and flat worms (trematodes).

<i>Heligmosomoides polygyrus</i> Species of roundworm

Heligmosomoides polygyrus, previously named Nematospiroides dubius, is a naturally occurring intestinal roundworm of rodents. It belongs to the family Trychostrongylidae, and male and female worms are morphologically distinguishable. The parasite has a direct lifecycle, with its larval form being the infective stage. H. polygyrus has the ability to establish chronic infections in rodents and alter host immune responses. This nematode is widely used as a gastrointestinal parasitic model in immunological, pharmacological, and toxicological studies.

Dientamoebiasis is a medical condition caused by infection with Dientamoeba fragilis, a single-cell parasite that infects the lower gastrointestinal tract of humans. It is an important cause of traveler's diarrhea, chronic abdominal pain, chronic fatigue, and failure to thrive in children.

<i>Trichuris</i> Genus of roundworms

Trichuris, often referred to as whipworms, is a genus of parasitic worms from the roundworm family Trichuridae, which are helminths. The name whipworm refers to the shape of the worm; they look like whips with wider "handles" at the posterior end. The name Trichocephalus is sometimes used for this genus.

Capillaria philippinensis is a parasitic nematode which causes intestinal capillariasis. This sometimes fatal disease was first discovered in Northern Luzon, Philippines, in 1964. Cases have also been reported from China, Egypt, Indonesia, Iran, Japan, Korea, Lao PDR, Taiwan and Thailand. Cases diagnosed in Italy and Spain were believed to be acquired abroad, with one case possibly contracted in Colombia. The natural life cycle of C. philippinensis is believed to involve fish as intermediate hosts, and fish-eating birds as definitive hosts. Humans acquire C. philippinensis by eating small species of infested fish whole and raw.

Parasitic worm, also known as helminth, is large macroparasite.

<i>Toxascaris leonina</i> Species of roundworm

Toxascaris leonina is a common parasitic roundworm found in dogs, cats, foxes, and related host species. T. leonina is an ascarid nematode, a worldwide distributed helminth parasite which is in a division of eukaryotic parasites that, unlike external parasites such as lice and fleas, live inside their host. The definitive hosts of T. leonina include canids and felines (cats), while the intermediate hosts are usually rodents, such as mice or rats. Infection occurs in the definitive host when the animal eats an infected rodent. While T. leonina can occur in either dogs or cats, it is far more frequent in cats.

<span class="mw-page-title-main">Pinworm infection</span> Medical condition

Pinworm infection, also known as enterobiasis, is a human parasitic disease caused by the pinworm, Enterobius vermicularis. The most common symptom is itching in the anal area. The period of time from swallowing eggs to the appearance of new eggs around the anus is 4 to 8 weeks. Some people who are infected do not have symptoms.

<i>Heterophyes heterophyes</i> Species of fluke

Heterophyes heterophyes, or the intestinal fish fluke, was discovered by Theodor Maximaillian Bilharz in 1851. This parasite was found during an autopsy of an Egyptian mummy. H. heterophyes is found in the Middle East, West Europe and Africa. They use different species to complete their complex lifestyle. Humans and other mammals are the definitive host, first intermediate host are snails, and second intermediate are fish. Mammals that come in contact with the parasite are dogs, humans, and cats. Snails that are affected by this parasite are the Cerithideopsilla conica. Fish that come in contact with this parasite are Mugil cephalus, Tilapia milotica, Aphanius fasciatus, and Acanthgobius sp. Humans and mammals will come in contact with this parasite by the consumption of contaminated or raw fish. This parasite is one of the smallest endoparasite to infect humans. It can cause intestinal infection called heterophyiasis.

<i>Raillietina</i> Genus of flatworms

Raillietina is a genus of tapeworms that includes helminth parasites of vertebrates, mostly of birds. The genus was named in 1920 in honour of a French veterinarian and helminthologist, Louis-Joseph Alcide Railliet. Of the 37 species recorded under the genus, Raillietina demerariensis, R. asiatica, and R. formsana are the only species reported from humans, while the rest are found in birds. R. echinobothrida, R. tetragona, and R. cesticillus are the most important species in terms of prevalence and pathogenicity among wild and domestic birds.

<i>Dientamoeba fragilis</i> Parasite of humans, pigs and gorillas

Dientamoeba fragilis is a species of single-celled excavates found in the gastrointestinal tract of some humans, pigs and gorillas. It causes gastrointestinal upset in some people, but not in others. It is an important cause of travellers diarrhoea, chronic diarrhoea, fatigue and, in children, failure to thrive. Despite this, its role as a "commensal, pathobiont, or pathogen" is still debated. D. fragilis is one of the smaller parasites that are able to live in the human intestine. Dientamoeba fragilis cells are able to survive and move in fresh feces but are sensitive to aerobic environments. They dissociate when in contact or placed in saline, tap water or distilled water.

<i>Huffmanela</i> Genus of roundworms

Huffmanela is a genus of parasitic nematodes, belonging to the family Trichosomoididae.

Anguillicoloides novaezelandiae is a parasitic nematode worm that lives in the swimbladders of eels, particularly Anguilla australiensis, Anguilla anguilla and Anguilla dieffenbachii. Specimens have been located in Italy and New Zealand. The species is most similar to A. Australiensis. However, it differs from the latter species in the shape of the head end which is bulbously inflated, almost spherical, and followed by a marked neck constriction in A. Australiensis, whereas it is only slightly expanded in A. novaezelandiae. Also, the anterior ovary in A. australiensis females extends anteriorly to about the mid-length of the oesophagus, while it does not reach the end of the oesophagus in A. novaezelandiae. Both species differ in size and form. While the body of A. australiensis is long and relatively slender, that of A. novaezelandiae is much shorter and wider. The shape of the posterior end of the female body is different in these two species.

References

This page is based on this Wikipedia article
Text is available under the CC BY-SA 4.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.