pinworm

(click to enlarge)
Pinworm (Enterobius vermicularis) (credit: Walter Dawn)

Common species (Enterobius vermicularis) of nematode parasitic to humans, especially children. Female pinworms may be 0.5 in. (13 mm) long; males are much smaller. Pinworms have a very long tail that gives them a pinlike appearance. They mate in the upper gastrointestinal tract, usually in the large intestine; the females travel to the anus, deposit their fertilized eggs on the skin near the anal opening, and die. The worms' movements cause itching; eggs transferred to the fingernails when the victim scratches may be passed to the mouth. Eggs can also be inhaled with air dust. The eggs or larvae make their way to the intestine, and the cycle begins again.

For more information on pinworm, visit Britannica.com.

Definition

Pinworms, Enterobius vermicularis, are small, white worms that can live in the intestines, are common in young children, and are easily treated.

Description

Adult pinworms live in the large intestines. Males and females are about 5 mm and 10 mm long, respectively, with the diameter of a strand of thread. After copulation, the males die. When the female is ready to lay eggs, she crawls out of the anus, and violently expels the eggs on the skin around the anus. Some of the eggs become airborne and land elsewhere, but the majority stay on the skin of the buttocks. A single female can produce more than 10,000 eggs. After laying her eggs, the female also dies. At body temperature, the eggs develop quickly and are infective in about six hours. When ingested by another person, the eggs hatch in the small intestine. Juvenile worms grow into adult, sexually mature worms in about a month. These tiny worms are quite complex in that they have mouths, throats, gastrointestinal tracts, and a nervous system. The males and females have a complex reproductive tract and reproduce sexually. There is evidence that a protozoan parasite (Dientamoeba fragilis) is transmitted among humans in the eggs of pinworms. Thus, they may occur simultaneously.

Transmission

Pinworms are extremely contagious, and the eggs are infective within a few hours of being laid. They are usually spread from child to child by contaminated fingers. When children scratch their itchy bottoms, the tiny eggs get under their fingernails. As they move around the house or classroom, the eggs can be spread. Eggs can stay on a child's skin for several hours. They can survive for two weeks on clothes, bedding, and toys. Children who touch the contaminated materials and then place their fingers in their mouths have provided a route for the tiny eggs to enter their bodies. The eggs stay in the upper part of the intestine until they hatch, then move down the length of the intestine and out the anus to lay eggs, and the cycle continues. The entire life cycle lasts four to six weeks. Sometimes adults breathe in the eggs when the bed covers are shaken; however, this is very uncommon. Transmission easily occurs by children not washing their hands thoroughly and spreading the infection to others. It is for this reason that if one member of a family is infected with pinworms, the whole family is treated.

Demographics

The pinworm Enterobius vermicularis is one of the most common nematode parasitic infections of humans in North America and Europe. It is estimated that pinworms infect more than 400,000,000 people throughout the world or approximately 10 percent of humans. There are no differences in pinworm infections on the basis of race or socioeconomic class. Neither is pinworm infection an indication of poor hygiene. This is a very easily transmissible infection that is quite widespread in children. Since the majority of children experience no ill effects whatsoever, extreme measures to treat pinworms are not indicated.

Causes and Symptoms

Pinworm infections can be asymptomatic or result in mild gastrointestinal upsets. A common symptom associated with pinworm infections is perianal (around the anus) itching. Scratching of the perianal skin to relieve the itching can lead to bacterial infections that result in more itching, etc. Eventually, this cycle produces a great deal of discomfort. Children who are infected with pinworms often show symptoms that include restlessness, irritability, and insomnia. In females, the adult pinworms can enter the vagina and cause additional irritation. Since the pinworm almost always stays in the gastrointestinal tract or vagina, there is usually no systemic illness. A few children do develop intense nighttime itching of the skin around the anus. Girls who develop vaginal pinworm may experience vaginal itching or a vaginal discharge.

When to Call the Doctor

If the child seems restless at night and complains of itching in the morning, parents should call their health-care provider to obtain a pinworm lab kit. The kit consists of a tongue depressor with a piece of clear tape on the end. To use the kit, a parent should press the end of the tongue depressor, with the tape on it, against the child's anal skin. The tape is then placed, sticky-side down on a glass slide. The health-care provider will be able to see the eggs with a microscope, and the parent may even see them around the anus during the tape test.

Diagnosis

Stool and blood tests are not helpful in diagnosing pinworms. Seeing a worm is what determines the diagnosis. The parent must check the child's skin with a flashlight during the night and the first thing in the morning and look for white, wiggling threads. Occasionally a wiggling worm may be seen on the surface of a stool. Since pinworms are so common, children with nighttime anal itching are often treated without any lab test. The classic diagnostic tool is to apply a piece of transparent tape to the skin near the anus first thing in the morning. The health-care provider can attach it to a glass slide and then examine it under a microscope for the presence of eggs. A pinworm lab kit can usually be supplied by a provider's office if necessary.

Treatment

Treatment is with a single dose of an anti-pinworm drug such as albendazole (Albenza) or mebendazole (Vermox). Vermox comes as a chewable tablet and most children, as well as adults, experience no side effects with the medication. Allergic reactions have been rarely reported, and very rare cases of convulsions have occurred. The medication kills the worms about 95 percent of the time, but it does not kill the eggs. Therefore, retreatment in two weeks is recommended. Girls with vaginal itching alone do not necessarily need treatment, since the problem will often disappear on its own. Many healthcare providers disagree as to whether to treat the whole family, while others believe it is essential to treat the entire household. It is possible that a girl may be an asymptomatic carrier, which results in numerous reinfections. If everyone is treated, however, this problem will be alleviated. If the child is over two years of age, Pin-X (pyrantel pamoate) is an over-the-counter alternative to Vermox that is available as a liquid.

Prognosis

Treatment is usually very successful if followed with the prevention guidelines to prevent reinfection and doing a retreatment within two weeks after the first.

Prevention

Pinworm infections and reinfections can be diminished by the following:

• Make certain children wash their hands before meals and after using the restroom.
• Keep children's fingernails trimmed.
• Discourage nail-biting and scratching the anal area.
• Have children change into a clean pair of underwear each day.
• Have children bathe in the morning to reduce egg contamination.
• Open bedroom blinds and curtains during the day as eggs are sensitive to sunlight.
• After each treatment, change night clothes, underwear, and bedding and wash them.

Parental Concerns

Since pinworms are so common and usually occur in children age 12 and under, there is no reason for concern unless the infection keeps reoccurring. In that case, meticulous cleaning and treatment with retreatment needs to be enforced.

Resources

Organizations

American Academy of Pediatrics. 141 Northwest Point Blvd., Elk Grove Village, IL 60007-1098. (847) 434-4000. Web site: www.aap.org.

Web Sites

Center of Disease Control and Prevention. Fact Sheet:Pinworms [cited March 6, 2005]. Available online at: .

iVillage. Pinworms: Why do they keep coming back? [cited March 6, 2005]. Available online at: www.parentsplace.com/toddlers/health/qas/0,,239278_101260,00.html.

Ohio State University. Pinworms. [cited March 6, 2005]. Available online at: www.biosci.ohio-state.edu/~parasite/enterobius.html.

[Article by: Linda K. Bennington, MSN, CNS]

Any oxyurid, especially Oxyuris equi and Probstmayria vivipara both in horses, Passalurus ambiguus in rabbits, Syphacia obvelata in hamster and mouse.

Pinworm ICD 127.4
Scientific classification
Kingdom:	Animalia
Phylum:	Nematoda
Class:	Secernentea
Subclass:	Spiruria
Order:	Oxyurida
Family:	Oxyuridae
Genus:	Enterobius
Species
Enterobius vermicularis (Linnaeus, 1758)[1] Enterobius anthropopitheci (Gedoelst, 1916)[1] Enterobius gregorii (Hugot, 1983) (disputed)[2][3][4]

The pinworm (Genus Enterobius), also known as threadworm or seat worm, is a common human intestinal parasite, especially in children.^[5] The medical condition associated with pinworm infestation is known as enterobiasis,^[6] or sometimes oxyuriasis.^[7]

Unless otherwise noted, throughout this article the word pinworm refers to the species Enterobius vermicularis, which affects humans.

Contents 1 Classification 2 Morphology 3 Habitat 4 Life cycle 5 Reproduction 6 Effects 7 Diagnosis 8 Treatment 9 Additional images 10 See also 11 Notes 12 References 13 External links

Classification

The pinworm is a a type of roundworm, and two species of pinworm have been identified with certainty.^[8] Humans are host only to Enterobius vermicularis (formerly Oxyuris vermicularis).^[9] Chimpanzees are host to Enterobius anthropopitheci, which is morphologically distinguishable from the human pinworm.^[3]. Hugot 1983 claims there is another species affecting humans, Enterobius gregorii, which is supposedly a sister species of E. vermicularis, and has a slightly smaller spicule.^[10] Its existence is controversial however; Totkova et al. consider there to be insufficient evidence^[4], and Hasagawa et al. contend that E. gregorii is a younger stage of E. vermicularis.^[2][3] Regardless of its status as a distinct species, E. gregorii is considered clinically identical to E. vermicularis.^[9]

Two female pinworms next to a ruler. The markings are one millimeter apart.

Morphology

The pinworm appears as a white, small and delicate nematode.^[11] The adult female has a sharply pointed posterior end, is 8 to 13 millimeters long, and 0.5 millimeters thick.^[11] The adult male is considerably smaller, measuring 2 to 5 millimeters long and 0.2 millimeters thick, and has a curved posterior end.^[11] The eggs are translucent, and may contain a developing embryo or a fully developed larva.^[11] The eggs have a thick shell that is flattened on one side, and measure 50 to 60 micrometers by 20 to 30 micrometers.^[11]

Habitat

The pinworm lives in the large intestine, especially in the cecum.^[11] They only have one host during their lifetime.^[11]

It is found worldwide, and causes the most common infection enterobiasis in humans. Unlike many other intestinal parasites, the pinworm does not usually enter the bloodstream or any other organs besides the intestines. In some cases, pinworms can enter the vagina (where they soon die),^[12] and much more rarely, the uterus, fallopian tubes, liver, and peritoneum, but the worms cannot survive long in these places.

The human pinworm Enterobius vermicularis is an ubiquitous parasite of humans, it being estimated that over 200 million people are infected annually. It is more common in the temperate regions of Western Europe and North America (its existence is relatively rare in the tropics), and is found particularly in children. Samples of Caucasian children in the U.S.A. and Canada have shown incidences of infection of between 30% to 80%, with similar levels in Europe.^[13] Children are more likely than adults to acquire the infestation because they are more likely to play with soil and mud and insert their fingers in their mouths without washing them first.

Pinworm life cycle.

Life cycle

After mating, the females migrate from the cecum to the rectum, where they emerge from the anus and lay eggs on the skin around the anus.^[11] After the eggs have been ingested, the larvae develop to adults in the intestine.^[11] The entire life cycle is complete within 4 to 6 weeks, with 30 days being the best estimate.^[14]

Reproduction

Pinworms mate by traumatic insemination. After mating, the male dies. The female migrates to the anus and emerges, usually during the night, to deposit about 10,000 to 20,000 eggs in the perianal area (around the anus). She then secretes a substance which causes a very strong itching sensation, inciting the host to scratch the area and thus transfer some of the eggs to the fingers. Eggs can also be transferred to cloth, toys, and the bathtub. Once ingested orally, the larvae hatch in the small intestine, specifically the duodenum, and migrate back to the large intestine where they mature. Maturity is reached in 30–45 days. The eggs can survive for 2 to 3 weeks on their own outside of the human body. In some cases, the larvae will hatch in the peri-anal area and travel back inside the anus, up the rectum, and back into the intestines where they mature.^[15]

Effects

Except for itching, pinworm infestation does not usually cause any direct damage to the body. However, the unsanitary scratching of the itch can spread germs from the fingers to other parts of the body. This scratching occurs even as the person is asleep and can easily contribute to unhealthy skin conditions or infections. Sleep disturbance may arise from the itching or crawling sensations. Some case reports suggest that severe infestation may be associated with an increased risk for appendicitis. There is also some evidence of an association between enterobiasis and diminished zinc levels.^{[citation needed]}

Diagnosis

Diagnosis is often made clinically by observing the female worm (or many worms) in the peri-anal region, but can also be made using the "scotch-tape" test, in which the sticky side of a strip of cellophane tape is pressed against the peri-anal skin, then examined under a microscope for pinworm eggs.

Self-diagnosis is also possible without observing worms around the anus. Crawling sensations inside the anus indicate female pinworm migration, and they may be visually detected at this time by using lubricant to insert a finger into the anus, hooking it slightly, and pulling the finger out while at the same time gently scraping the rectal wall.^{[citation needed]} This may cause some of the thread-like pinworms to adhere to the lubricated finger, and they may thus be extracted from the anus. The method requires a sufficient number of repetitions, and scraping of all sides of the rectal wall. The method can also be used to provide temporary relief from intense crawling sensations caused by large numbers of pinworms in the lower rectal area, simply by manually removing some of them.^{[citation needed]}

The pinworms may be seen in the host's faeces; however the eggs are invisible to the naked eye.

The diagnostic characteristics are: size 50-60 µm by 20-32 µm; typical elongated shape, with one convex side and one flattened side and colorless shell ^[16].

On histologic cross section, alae or wings (running the length of the worm) are identifying features of the pinworm (see micrograph).^[17]

Treatment

Antihelmintic drugs albendazole (Albenza), mebendazole (Vermox, OVEX), Piperazine and pyrantel pamoate (Pin-X, Reese's Pinworm Medication) are commonly used to treat pinworms; these medicines kill the pinworms 95% of the time, but do not kill the eggs. The person being treated should receive a second course after two weeks.

Additional images

Pinworms are sometimes diagnosed incidentally by pathology. Micrograph of pinworms in the appendix. H&E stain.	High magnification micrograph of a pinworm in cross section in the appendix. H&E stain.	High magnification micrograph of a pinworm in cross section in the appendix. H&E stain.	Enterobius vermicularis egg under a light microscope.
Pinworms are sometimes diagnosed incidentally by pathology. Micrograph of male pinworm in cross section. Alae (blue arrow), intestine (red arrow) and testis (black arrow). H&E stain.	Pinworm eggs are easily seen under a microscope.	This micrograph reveals the cephalic alae in the head region of Enterobius vermicularis.

See also

• List of parasites (human)

Notes

1. ^ ^{a b} Hasegawa et al. 2005.
2. ^ ^{a b} Hasegawa et al. 1998
3. ^ ^{a b c} Hasegawa et al. 2006
4. ^ ^{a b} Totkova et al. 2003
5. ^ Encyclopedia Britannica.
6. ^ Merriam-Webster: Enterobiasis
7. ^ Merriam-Webster: Oxyuriasis
8. ^ NCBI taxonomy database 2009
9. ^ ^{a b} dpdx 2009
10. ^ Hugot 1983
11. ^ ^{a b c d e f g h i} Gutiérrez 2005, p. 354.
12. ^ http://www.informahealthcare.com/doi/abs/10.1517/14656566.2.2.267?cookieSet=1&journalCode=eop
13. ^ The Human Pinworm
14. ^ Gutiérrez 2005, p. 355.
15. ^ Rudolph's Pediatrics - 21st Ed. 2003; Current Medical Diagnosis & Treatment - 45th Ed. 2006
16. ^ "PARASITOLOGY - CHAPTER FOUR NEMATODES (Round Worms)". The Board of Trustees of the University of South Carolina. http://pathmicro.med.sc.edu/parasitology/nematodes.htm. Retrieved 2007-10-18. 
17. ^ Diagnostic Findings Enterobiasis. Centers for Disease Control and Prevention. URL: http://www.dpd.cdc.gov/dpdx/HTML/Enterobiasis.htm. Accessed on: August 6, 2008.

References

• Hasegawa, Hideo; Yatsukaho Ikeda, Akiko Fujisaki, Liza R. Moscovice, Klara J. Petrzelkova, Taranjit Kaur, and Michael A. Huffman (2005). "MORPHOLOGY OF CHIMPANZEE PINWORMS, ENTEROBIUS (ENTEROBIUS) ANTHROPOPITHECI (GEDOELST, 1916) (NEMATODA: OXYURIDAE), COLLECTED FROM CHIMPANZEES, PAN TROGLODYTES, ON RUBONDO ISLAND, TANZANIA" (PDF). Journal of Parasitology, 91(6), 2005. American Society of Parasitologists. pp. 1314–1317. http://www.bush2base.vt.edu/publications/2005%20Kaur_Hideo%20JParas.pdf. Retrieved 2009-04-08. 
• "Pinworm". Encyclopædia Britannica. http://www.britannica.com/EBchecked/topic/461262/pinworm. Retrieved 2009-04-08. 
• "Enterobiasis". Merriam-Webster's Medical Dictionary. Merriam-Webster. http://www.merriam-webster.com/medical/enterobiasis. Retrieved 2009-04-08. 
• "Oxyuriasis". Merriam-Webster's Medical Dictionary. Merriam-Webster. http://www.merriam-webster.com/dictionary/oxyuriasis. Retrieved 2009-04-08. 
• Totkova A, Klobusicky M, Holkova R, Valent M (2003). "Epidemological Study: Enterobius Gregorii - Reality or Fiction?" (PDF). Bratisl Lek Listy 2003; 104 (3). Bratislava Medical Journal. pp. 130-133. http://www.bmj.sk/2003/10403-06.pdf. Retrieved 2009-04-08. 
• "Enterobius". NCBI taxonomy database. National Center for Biotechnology Information, U.S. National Library of Medicine. 2009. http://www.ncbi.nlm.nih.gov/Taxonomy/Browser/wwwtax.cgi?mode=Tree&id=51027&lvl=3&lin=f&keep=1&srchmode=1&unlock. Retrieved 2009-04-08. 
• "Enterobiasis". DPDx. Division of Parasitic Diseases, Centers for Disease Control and Prevention. http://www.dpd.cdc.gov/DPDx/html/Enterobiasis.htm. Retrieved 2009-04-08. 
• Hasegawa, Hideo; Tadao Nakano, Munehiro Okamoto, Yatsukaho Ikeda (2006). "Mitochondrial cytochrome c oxidase subunit 1 gene and nuclear rDNA regions of Enterobius vermicularis parasitic in captive chimpanzees with special reference to its relationship with pinworms in humans". Springer-Verlag. http://parasitology.informatik.uni-wuerzburg.de/login/n/h/j_436-100-1-2006-06-21-238.html.html. Retrieved 2009-04-08. 
• Hugot, JP (1983). "Enterobius gregorii (Oxyuridae, Nematoda), a new human parasite". Ann Parasitol Hum Comp 1983;58(4). National Center for Biotechnology Information. pp. 403-4. http://www.ncbi.nlm.nih.gov/pubmed/6416131?dopt=Abstract. Retrieved 2008-04-09. 
• Hasegawa H, Takao Y, Nakao M, Fukuma T, Tsuruta O, Ide K (1998). "Is Enterobius gregorii Hugot, 1983 (Nematoda: Oxyuridae) a distinct species?". Journal of Parasitology 1998 Feb;84(1). National Center for Biotechnology Information. pp. 131-4.. http://www.ncbi.nlm.nih.gov/pubmed/9488350?. Retrieved 2008-04-09. 
• Gutiérrez, Yezid (2000) (PDF). Diagnostic pathology of parasitic infections with clinical correlations (Second ed.). Oxford University Press. pp. 354–366. ISBN 0195121430. http://books.google.fi/books?id=oKSEhVMVrJ4C&lpg=PP1&ots=Wh5-BxVqNC&dq=Guti%C3%A9rrez%2C%20Yezid&pg=PA354#v=onepage&q=&f=false. Retrieved 21 August 2009. 

External links

• New England Journal of Medicine Video of infected colon
• NHS Direct Health encyclopaedia - Threadworms
• Experiences about Threadworm (Patient UK forum)
• Pinworm facts, life cycle, references at MetaPathogen
• Pinworms eliminated by Vitaklenz Treatment

v • d • e Infectious diseases · Parasitic disease: helminthiases (B65-B83, 120-129) Flatworm/ platyhelminth Fluke/trematode (Trematode infection) Blood fluke Schistosoma mansoni/japonicum/mekongi/haematobium (Schistosomiasis) · Trichobilharzia regenti (Swimmer's itch) Liver fluke Clonorchis sinensis (Clonorchiasis) · Fasciola hepatica/gigantica (Fascioliasis) · Opisthorchis Lung fluke Paragonimus westermani (Paragonimiasis) Intestinal fluke Fasciolopsis buski (Fasciolopsiasis) Cestoda (Tapeworm infection) Cyclophyllidea Echinococcus granulosus/Echinococcus multilocularis (Echinococcosis) · Taenia saginata (beef)/Taenia solium (pork) (Taeniasis/Cysticercosis) · Hymenolepis nana/Hymenolepis diminuta (Hymenolepiasis) Pseudophyllidea Diphyllobothrium latum (Diphyllobothriasis) · Spirometra erinaceieuropaei (Sparganosis) · Diphyllobothrium mansonoides (Sparganosis) Roundworm/nematode (Nematode infection) Secernentea Spirurida Camallanina Dracunculus medinensis (Dracunculiasis) Spirurina Filarioidea (Filariasis) Onchocerca volvulus (Onchocerciasis) · Loa loa (Loa loa filariasis) · Mansonella (Mansonelliasis) · Dirofilaria repens (Dirofilariasis) Wuchereria bancrofti · Brugia malayi · Brugia timori Thelazioidea Gnathostoma (Gnathostomiasis) · Thelazia (Thelaziasis) Spiruroidea Gongylonema Strongylida (hookworm) Ancylostoma duodenale/Ancylostoma braziliense (Ancylostomiasis, Cutaneous larva migrans) · Necator americanus (Necatoriasis) · Angiostrongylus cantonensis (Angiostrongyliasis) · Metastrongylus (Metastrongylosis) Ascaridida Ascaris lumbricoides (Ascariasis) · Anisakis (Anisakiasis) · Toxocara canis/Toxocara cati (Visceral larva migrans/Toxocariasis) · Baylisascaris Rhabditida Strongyloides stercoralis (Strongyloidiasis) Oxyurida Enterobius vermicularis (Enterobiasis · Pinworm) Adenophorea Trichinella spiralis (Trichinosis) · Trichuris trichiura (Trichuriasis · Whipworm) · Capillaria philippinensis (Intestinal capillariasis) · Capillaria hepatica see also drugs

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Dansk (Danish)
n. - børneorm

Nederlands (Dutch)
rond-/draadworm

Français (French)
n. - ver parasite

Deutsch (German)
n. - (zo.) Madenwurm

Ελληνική (Greek)
n. - σκωληκοειδίτιδα

Italiano (Italian)
ossiuro

Português (Portuguese)
n. - oxiúro (m) (Med.)

Русский (Russian)
глист

Español (Spanish)
n. - lombriz intestinal

Svenska (Swedish)
n. - nematod (parasit), mask

中文（简体）(Chinese (Simplified))
蛲虫

中文（繁體）(Chinese (Traditional))
n. - 蟯蟲

한국어 (Korean)
n. - 요충

日本語 (Japanese)
n. - 蟯虫

العربيه (Arabic)
‏(الاسم) الدودة الدبوسيه : دودة خيطيه صغيرة‏

עברית (Hebrew)
n. - ‮תולעת טפילית‬

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