Enterobiasis pathophysiology: Difference between revisions

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Latest revision as of 21:35, 29 July 2020

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Furqan M M. M.B.B.S [2]

Overview

Enterobius vermicularis is usually transmitted via the feco-oral route to the human host. It reproduces in the small intestine of humans only. The gravid female worm lays eggs in the perianal area usually at night and causes pruritus. In addition to the fingernail contamination, the infective eggs can be transmitted via the dust and fomites.

Pathophysiology

Pathogenesis

It is postulated that Enterobius vermicularis triggers an inflammatory response which is associated with the low-grade eosinophilia.
Allergic response to the worm protein is considered the cause of pruritus; usually pruritus ani (perianal pruritus).^[1]

Lifecycle

The lifecycle of Enterobius vermicularis is completed in the human host and comprises of the following stages:^[2]^[3]

The infective eggs of E. vermicularis are ingested via contaminated hands or fomites (clothing, toys, bed, furniture, animals' fur etc). The eggs mature into adult Enterobius in 15-40 days.
Male adult larvae fertilize the female (in lower ileum) and are passed out in stools without producing symptoms. Adult females settle in the lower ileum, caecum, appendix and ascending colon. The gravid worm migrates from the colon to the rectal area. At night eggs laid on the perianal skin by the uterine contraction(s) of the gravid worm.
At oviposition, the eggs are immature and non-infective. They become infective within 6 hours at body temperature.
In cool, moist environment with little ventilation eggs remain viable for up to three weeks. However, the infectivity decreases with time. Eggs do not tolerate heat that well which might be the reason that enterobiasis is more common in temperate than tropical climates.
In rare cases, pinworms are found in the vagina and even more rarely in the uterus, fallopian tubes, liver, and peritoneum, but the worms cannot survive long in these places.

The image shown below depicts the life cycle of the pinworm.^[4]

Enterobius Lifecycle — *Enterobius* Lifecycle

Mode of Transmission

E. Vermicularis is transmitted via these four modes:^[2]

Direct infection from the anal and perianal regions by infected fingernails.
Exposure to viable eggs on fomites (clothing, toys, bed, furniture, fur of pets etc).
By dust contaminated with embryonated (infected) eggs.
Retroinfection; migration of the larvae into sigmoid colon & caecum after hatching on the anal mucosa.

Image

Life cycle of Enterobius vermicularis, otherwise known as the human pinworm. From Public Health Image Library (PHIL). ^[5]

References

↑ Katz, Michael (1989). Parasitic Diseases. New York, NY: Springer US. ISBN 978-1-4684-0327-5.
↑ ^2.0 ^2.1 Cook GC (1994). "Enterobius vermicularis infection". Gut. 35 (9): 1159–62. PMC 1375686. PMID 7959218.
↑ Caldwell JP (1982). "Pinworms (enterobius vermicularis)". Can Fam Physician. 28: 306–9. PMC 2306321. PMID 21286054.
↑ "CDC - Enterobiasis - Biology".
↑ "Public Health Image Library (PHIL)".

Template:WH Template:WS

[Parasitic_diseases-1] Katz, Michael (1989). Parasitic Diseases. New York, NY: Springer US. ISBN 978-1-4684-0327-5.

[pmid7959218-2] 2.0 ^2.1 Cook GC (1994). "Enterobius vermicularis infection". Gut. 35 (9): 1159–62. PMC 1375686. PMID 7959218.

[pmid21286054-3] Caldwell JP (1982). "Pinworms (enterobius vermicularis)". Can Fam Physician. 28: 306–9. PMC 2306321. PMID 21286054.

[urlCDC_-_Enterobiasis_-_Biology-4] "CDC - Enterobiasis - Biology".

[PHIL-5] "Public Health Image Library (PHIL)".

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[2]

[3]

[4]

[5]

@@ Line 1: / Line 1: @@
 __NOTOC__
-{{Pinworm}}
+{{Enterobiasis}}
-{{CMG}}
+{{CMG}}; {{AE}} {{MMF}}
-Please help WikiDoc by adding more content here. It's easy!  Click  [[Help:How_to_Edit_a_Page|here]]  to learn about editing.
+==Overview==
+''[[Enterobius vermicularis]]'' is usually transmitted via the feco-oral route to the human host. It reproduces in the small intestine of humans only. The gravid female worm lays eggs in the perianal area usually at night and causes pruritus. In addition to the fingernail contamination, the infective eggs can be transmitted via the dust and fomites.
 ==Pathophysiology==
-[[Image:Enterobius vermicularis LifeCycle.gif|180 px|Left]]
-===Forms of Worm===
-The best known is the human pinworm ''[[Enterobius vermicularis]]'' and the more recently discovered ''[[Enterobius gregorii]]''. The adult pinworm male is 1&ndash;4&nbsp;[[millimetre|mm]] in length, while the adult female is 8&ndash;13 mm and possesses the long, pin-shaped posterior for which the worm is named. The human pinworm is commonly found in children, but adults may also be affected.
-===Habitat===
-The pinworm lives in the large intestine and cecum. It is found worldwide, and causes the most common infection [[enterobiasis]] in humans. Unlike many other [[intestinal parasite]]s, the pinworm does not usually enter the [[bloodstream]] or any other organs besides the intestines. Only in rare cases pinworms are found in the [[vagina]], and even more rarely in the [[uterus]], [[fallopian tube]]s, [[liver]], and [[peritoneum]], but the worms cannot survive long in these places.
-The human pinworm ''Enterobius vermicularis'' is a ubiquitous parasite of man, 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, (it being 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.
+===Pathogenesis===
-===Reproduction===
+*It is postulated that ''[[Enterobius vermicularis]]'' triggers an inflammatory response which is associated with the low-grade [[eosinophilia]].
-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 [[egg (biology)|egg]]s in the perianal area (around the anus). She then secretes a substance which causes a very strong [[itch]]ing 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 [[larva|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.<ref>Rudolph's Pediatrics - 21st Ed. 2003; Current Medical Diagnosis & Treatment - 45th Ed. 2006</ref>
+*Allergic response to the worm protein is considered the cause of [[pruritus]]; usually pruritus ani (perianal pruritus).<ref name="Parasitic diseases">{{cite book | last = Katz | first = Michael | title = Parasitic Diseases | publisher = Springer US | location = New York, NY | year = 1989 | isbn = 978-1-4684-0327-5 }}</ref>
+====Lifecycle====
+The lifecycle of ''[[Enterobius vermicularis]]'' is completed in the human host and comprises of the following stages:<ref name="pmid7959218">{{cite journal |vauthors=Cook GC |title=Enterobius vermicularis infection |journal=Gut |volume=35 |issue=9 |pages=1159–62 |year=1994 |pmid=7959218 |pmc=1375686 |doi= |url=}}</ref><ref name="pmid21286054">{{cite journal |vauthors=Caldwell JP |title=Pinworms (enterobius vermicularis) |journal=Can Fam Physician |volume=28 |issue= |pages=306–9 |year=1982 |pmid=21286054 |pmc=2306321 |doi= |url=}}</ref>
+*The infective eggs of ''[[Enterobius vermicularis|E. vermicularis]]'' are ingested via contaminated hands or fomites (clothing, toys, bed, furniture, animals' fur etc). The eggs mature into adult Enterobius in 15-40 days.
+*Male adult larvae fertilize the female (in lower ileum) and are passed out in stools without producing symptoms. Adult females settle in the lower [[ileum]], [[caecum]], [[appendix]] and [[ascending colon]]. The gravid worm migrates from the colon to the rectal area. At night eggs laid on the perianal skin by the uterine contraction(s) of the gravid worm.
+*At oviposition, the eggs are immature and non-infective. They become infective within 6 hours at body temperature.
+*In cool, moist environment with little ventilation eggs remain viable for up to three weeks. However, the infectivity decreases with time. Eggs do not tolerate heat that well which might be the reason that enterobiasis is more common in temperate than tropical climates.
+*In rare cases, pinworms are found in the vagina and even more rarely in the [[uterus]], [[fallopian tubes]], liver, and [[peritoneum]], but the worms cannot survive long in these places.
+The image shown below depicts the life cycle of the pinworm.<ref name="urlCDC - Enterobiasis - Biology">{{cite web |url=https://www.cdc.gov/parasites/pinworm/biology.html |title=CDC - Enterobiasis - Biology |format= |work= |accessdate=}}</ref>
+[[Image:E.vermicularis LifeCycle.gif|center|''Enterobius'' Lifecycle]]
 ===Mode of Transmission===
-Pinworm eggs spread directly from person to person. They can also be spread by touching bedding, food, or other items contaminated with the eggs. Typically, children are infected by unknowingly touching pinworm eggs and putting their fingers in their mouths. The eggs are swallowed, and eventually hatch in the small intestine. The worms mature in the colon. Female worms then move to the child's anal area, especially at night, and deposit more eggs. This may cause intense itching. The area may even become infected. The itching will often lead to re-infection as the [[Egg (biology)|egg]]s are captured under the [[fingernail]]s, and eventually reintroduced orally. The eggs can also be spread by air and other mechanisms eventually leading to oral introduction into the victim.
+''[[Enterobius vermicularis|E. Vermicularis]]'' is transmitted via these four modes:<ref name="pmid7959218">{{cite journal |vauthors=Cook GC |title=Enterobius vermicularis infection |journal=Gut |volume=35 |issue=9 |pages=1159–62 |year=1994 |pmid=7959218 |pmc=1375686 |doi= |url=}}</ref>
-===Histopathology===
+#Direct infection from the anal and perianal regions by infected fingernails.
-'''Histopathology of appendix showing pinworms'''
+#Exposure to viable eggs on fomites (clothing, toys, bed, furniture, fur of pets etc).
-{{#ev:youtube|PkemlmA_tf0}}
+#By dust contaminated with embryonated (infected) eggs.
+#Retroinfection; migration of the larvae into sigmoid colon & caecum after hatching on the anal mucosa.
+==Image==
+<gallery>
+Image: Pinworm05.jpeg| Life cycle of Enterobius vermicularis, otherwise known as the ''human pinworm''. <SMALL><SMALL>''[http://phil.cdc.gov/phil/home.asp From Public Health Image Library (PHIL).] ''<ref name=PHIL> {{Cite web | title = Public Health Image Library (PHIL) | url = http://phil.cdc.gov/phil/home.asp}}</ref></SMALL></SMALL>
+</gallery>
 ==References==
 {{reflist|2}}
+{{WH}}
+{{WS}}
 [[Category:Needs overview]]
-[[Category:Needs content]]
 [[Category:Disease]]
 [[Category:Parasites]]
 [[Category:Nematodes]]
 [[Category:Proctology]]
+[[Category:Pediatrics]]
+[[Category:Emergency medicine]]
+[[Category:Up-To-Date]]
 [[Category:Infectious disease]]
-[[Category:Pediatrics]]{{WH}}
+[[Category:Gastroenterology]]
-{{WS}}