Editing Scabies (section)

== Cause ==
===Scabies mite===
{{Main|Sarcoptes scabiei}}
[[File:Sarcoptes scabiei.ogv|thumb|upright=1.3|alt=Video of the <nowiki>''</nowiki>Sarcoptes scabiei<nowiki>''</nowiki> mite|Video of the ''[[Sarcoptes scabiei]]'' mite]]
[[File:Scabies life cycle.png|thumb|upright=1.3|Lifecycle of scabies<ref name=cdc>{{cite web |url=http://www.dpd.cdc.gov/dpdx/HTML/Scabies.htm |title=Scabies |publisher=CDC Parasitology Diagnostic Web Site |access-date=2009-02-09 |url-status=dead |archive-url=https://web.archive.org/web/20090220123307/http://dpd.cdc.gov/dpdx/html/scabies.htm |archive-date=2009-02-20 }}</ref>]]

In the 18th century, Italian biologists [[Giovanni Cosimo Bonomo]] and [[Diacinto Cestoni]] (1637–1718) described the mite now called ''[[Sarcoptes scabiei]]'', variety ''hominis'', as the [[etiology|cause of]] scabies. ''Sarcoptes'' is a genus of skin parasites and part of the larger family of mites collectively known as scab mites. These organisms have eight legs as adults and are placed in the same phylogenetic class ([[Arachnida]]) as spiders and ticks.<ref>{{cite journal | vauthors = André HM |title=The true identity of Pascal's mite and the diachronic use of ciron |journal=Acarologia |date=30 June 2019 |volume=59 |issue=2 |pages=261–278 |doi=10.24349/acarologia/20194330 |language=en |issn=0044-586X|doi-access=free }}</ref>

''S. scabiei'' mites are under 0.5&nbsp;mm in size; they are sometimes visible as pinpoints of white.  Gravid females tunnel into the dead, outermost layer ([[stratum corneum]]) of a host's skin and deposit [[egg (biology)|eggs]] in the shallow burrows. The eggs hatch into [[larva]]e in three to ten days. These young mites move about on the skin and [[ecdysis|molt]] into a "[[nymph (biology)|nymphal]]" stage, before maturing as adults, which live three to four weeks in the host's skin. Males roam on top of the skin, occasionally burrowing into the skin. In general, the total number of adult mites infesting a healthy hygienic person with non-crusted scabies is small, about 11 females in burrows, on average.<ref name=autogenerated1/>

The movement of mites within and on the skin produces an intense itch, which has the characteristics of a delayed [[Cell-mediated immunity|cell-mediated inflammatory response]] to allergens. [[IgE]] antibodies are present in the serum and the site of infection, which react to multiple protein allergens in the body of the mite. Some of these cross-react to allergens from [[house dust mites]]. Immediate [[Antibody-mediated immunity|antibody-mediated allergic reactions]] (wheals) have been elicited in infected persons, but not in those not infected; immediate [[hypersensitivity]] of this type is thought to explain the observed far more rapid allergic skin response to reinfection seen in persons who have been infected previously, especially within the previous year or two.<ref name="autogenerated1"/>

===Transmission===
Scabies is [[Contagious disease|contagious]] and can be contracted through prolonged physical contact with an infested person.<ref name=ssd3>{{cite book |title=The Encyclopedia of Skin and Skin Disorders |url=https://archive.org/details/encyclopediaofsk0000turk |url-access=registration | vauthors = Turkington C, Dover JS |isbn=978-0-8160-6403-8 |year=2006 |publisher=Facts on File inc |location=New York}}</ref>  This includes [[sexual intercourse]], although a majority of cases are acquired through other forms of skin-to-skin contact.  Less commonly, scabies infestation can happen through the sharing of clothes, towels, and bedding, but this is not a major mode of transmission; individual mites can survive for only two to three days, at most, away from human skin at room temperature.<ref name=webmd>{{cite web |url=http://www.emedicinehealth.com/scabies/page2_em.htm#Scabies_Causes |title=Scabies Causes |access-date=2010-10-09 |website=WebMD |date=October 2010 |url-status=live |archive-url=https://web.archive.org/web/20100922170326/http://www.emedicinehealth.com/scabies/page2_em.htm#Scabies_Causes |archive-date=2010-09-22 }}</ref><ref name=chos>{{cite journal | vauthors = Chosidow O | title = Clinical practices. Scabies | journal = The New England Journal of Medicine | volume = 354 | issue = 16 | pages = 1718–1727 | date = April 2006 | pmid = 16625010 | doi = 10.1056/NEJMcp052784 }}</ref> As with lice, a [[latex condom]] is ineffective against scabies transmission during intercourse, because mites typically migrate from one individual to the next at sites other than the sex organs.<ref name=asha>{{cite web |url=http://www.ashastd.org/learn/learn_scabies_facts.cfm |title=Scabies – Fast Facts |access-date=2010-10-09 |publisher=American Social Health Association |url-status=dead |archive-url=https://web.archive.org/web/20110422110637/http://ashastd.org/learn/learn_scabies_facts.cfm |archive-date=2011-04-22 }}</ref>

Healthcare workers are at risk of contracting scabies from patients, because they may be in extended contact with them.<ref>{{cite journal | vauthors = FitzGerald D, Grainger RJ, Reid A | title = Interventions for preventing the spread of infestation in close contacts of people with scabies | journal = The Cochrane Database of Systematic Reviews | volume = 2014 | issue = 2 | pages = CD009943 | date = February 2014 | pmid = 24566946 | pmc = 10819104 | doi = 10.1002/14651858.CD009943.pub2 }}</ref>