Editing Crab louse

{{Short description|Species of insect}}
{{About|the animal|the infestation by crab or pubic lice|Phthiriasis pubis}}
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{{pp-semi-indef}}
{{Speciesbox
| name = Crab louse
| image = Crab louse (251 23) Female, from a human host.jpg
| genus = Pthirus
| species = pubis
| authority = ([[Carl Linnaeus|Linnaeus]], [[10th edition of Systema Naturae|1758]])
| synonyms =
* ''Pediculus pubis'' <small>Linnaeus, 1758</small>
* ''Phthirus pubis'' <small>[[William Elford Leach|Leach]], 1817<ref>{{cite web|url=http://phthiraptera.info/content/taxonomy-human-lice|title=Taxonomy of Human Lice|website=Phthiraptera.info|archive-url=https://web.archive.org/web/20200414211109/http://phthiraptera.info/content/taxonomy-human-lice|archive-date=April 14, 2020|url-status=dead}}</ref></small>
}}
The '''crab louse''' or '''pubic louse''' (''Pthirus pubis'') is an [[insect]] that is an [[obligate parasite|obligate]] [[Parasitism#Basic concepts|ectoparasite]] of [[human]]s, feeding exclusively on [[blood]].<ref name="Bolognia">{{cite book |author1=Rapini, Ronald P. |author2=Bolognia, Jean L. |author3=Jorizzo, Joseph L. |title=Dermatology: 2-Volume Set |publisher=Mosby |location=St. Louis |year=2007 |isbn=978-1-4160-2999-1 }}</ref> The crab louse usually is found in the person's [[pubic hair]]. Although the louse cannot jump, it can also live in other areas of the body that are covered with coarse hair, such as the [[Perineum|perianal area]], the general [[body hair]], and the [[eyelash]]es (in children).<ref name="cdc1">{{Cite web|url=https://www.cdc.gov/parasites/lice/index.html|title=Parasites: lice|author=CDC (Centers for Disease Control and Prevention)|website=www.cdc.gov|language=en-us|access-date=2017-12-04|date=2017-05-02}}{{PD-notice}}</ref><ref name="cdc2">{{Cite web|url=https://www.cdc.gov/parasites/lice/pubic/index.html|title=Parasites: pubic "crab" lice|author=CDC (Centers for Disease Control and Prevention)|website=www.cdc.gov|language=en-us|access-date=2017-12-04|date=2017-05-02}}{{PD-notice}}</ref>

Humans are the only known hosts of the crab louse, although a closely related species, ''[[Pthirus gorillae]]'', infects [[gorilla]]s. The human parasite is thought to have diverged from ''Pthirus gorillae'' approximately 3.3 million years ago.<ref>{{cite journal |journal=J Biol |date=10 February 2009 |volume=8 |issue=2 |pages=20 |title=Apes, lice and prehistory |author=Weiss RA |pmid=19232074 |pmc=2687769 |doi=10.1186/jbiol114 |doi-access=free }}</ref> It is more distantly related to the genus ''[[Pediculus]]'', which contains the human [[head louse|head]] and [[body louse|body lice]] and lice that affect [[Common chimpanzee|chimpanzee]]s and [[bonobo]]s.

==Description==
An adult crab louse is about 1.3–2&nbsp;mm long (slightly smaller than the [[body louse]] and [[head louse]]), and can be distinguished from those other species by its almost round body. Another distinguishing feature is that the second and third pairs of legs of a crab louse are much thicker than the front legs and have large claws.<ref name="service">{{cite book |author=Service, Mike |title=Medical Entomology for Students|publisher=Cambridge University Press|location=Cambridge|year=2012 |edition=5th|isbn=978-1-107-66818-8 }}</ref>

==Life cycle==
The eggs of the crab louse are laid usually on the coarse hairs of the [[Sex organ|genital]] and [[wikt:perianal|perianal]] regions of the human body. The female lays about three eggs a day. The eggs take 6–8 days to hatch, and there are three [[nymph (biology)|nymphal]] stages which together take 10–17 days before the adult develops, making a total life cycle from egg to adult of 16–25 days. Adults live for up to 30 days.<ref name="service"/> Crab lice feed exclusively on blood, and take a blood meal 4–5 times daily. Outside the host they can survive for 24–48 hours. Crab lice are transmitted from person to person most commonly via [[Human sexual activity|sexual contact]], although [[Fomite|fomites]] (bedding, clothing) may play a minor role in their transmission.<ref name="cdc3">{{Cite web|url=https://www.cdc.gov/parasites/lice/pubic/biology.html|title=Pubic "crab" lice: biology|author=CDC (Centers for Disease Control and Prevention)|website=www.cdc.gov|language=en-us|access-date=2017-12-04|date=2017-05-02}}{{PD-notice}}</ref>

==Infestation of humans==
{{Main|Pediculosis pubis}}
[[File:Pubic lice on eye-lashes.jpg|thumb|Crab lice on [[eyelash]]es]]
[[File:Crab louse 01.webm|thumb|Live louse magnified about 10x|right]]
[[File:Crab louse 02.webm|thumb|Live louse magnified about 10x|right]]
Infestation of the eyelashes is referred to as pediculosis ciliaris or phthiriasis palpebrarum.<ref>Manjunatha NP, Jayamanne GR, Desai SP, Moss TR, Lalik J, Woodland A. Pediculosis pubis: presentation to ophthalmologist as phthriasis palpebrarum associated with corneal epithelial keratitis. Int. J. STD AIDS 2006; 17: 424–426</ref>

The main symptom of infestation with crab lice is [[itch]]ing, usually in the pubic-hair area, resulting from [[hypersensitivity]] to louse saliva, which can become stronger over two or more weeks following initial infestation. In some infestations, a characteristic grey-blue or slate coloration appears (''maculae caeruleae'') at the feeding site, which may last for several days.{{citation needed|date=January 2021}}

[[File:Crab egg.jpg|thumb|right|175px|Crab louse egg on human body hair]]

The prevalence varies between 0.3% to 4.6% with an estimated average of 2% with an increase during war, disasters and in overcrowding.<ref name="l358">{{cite journal |last1=Patel |first1=P. U. |last2=Tan |first2=A. |last3=Levell |first3=N. J. |date=2021 |title=A clinical review and history of pubic lice |journal=Clinical and Experimental Dermatology |volume=46 |issue=7 |pages=1181–1188 |doi=10.1111/ced.14666 |pmid=33811771 |issn=1365-2230}}</ref> Crab louse infestations are not considered a reportable condition by many health authorities, and many cases are self-treated or treated discreetly by physicians.<ref>{{cite journal |vauthors=Anderson AL, Chaney E |title=Pubic lice (''Pthirus pubis''): history, biology and treatment vs. knowledge and beliefs of US college students |journal=Int J Environ Res Public Health |volume=6 |issue=2 |pages=592–600 |date=February 2009 |pmid=19440402 |pmc=2672365 |doi=10.3390/ijerph6020592 |doi-access=free }}</ref>

It has been suggested that an increasing percentage of humans [[Body grooming|removing]] their pubic hair, especially in women, has led to reduced crab louse populations in some parts of the world.<ref>{{Cite journal |last1 = Armstrong|first1 = N. R.|last2 = Wilson|first2 = J. D.
|title = Did the "Brazilian" kill the pubic louse?|doi = 10.1136/sti.2005.018671|journal = Sexually Transmitted Infections|volume = 82|issue = 3|pages = 265–266|year = 2006|pmid = 16731684|pmc =2564756}}</ref><ref>Bloomberg: [https://www.bloomberg.com/news/2013-01-13/brazilian-bikini-waxes-make-crab-lice-endangered-species-health.html Brazilian bikini waxes make crab lice endangered species], published 13 January 2013, retrieved 14 January 2013</ref>

[[File:Crab Lice CDC.png|thumb|right|300px|Crab lice]]
While crab lice are not known to transmit disease, the possibility has been raised they may be a vector for [[Bartonella|Bartonella spp]]. and [[Acinetobacter|Acinetobacter spp]] which might require further study.<ref name="l3582">{{cite journal |last1=Patel |first1=P. U. |last2=Tan |first2=A. |last3=Levell |first3=N. J. |date=2021 |title=A clinical review and history of pubic lice |journal=Clinical and Experimental Dermatology |volume=46 |issue=7 |pages=1181–1188 |doi=10.1111/ced.14666 |pmid=33811771 |issn=1365-2230}}</ref> In infested individuals an average of a dozen lice can be found. Although they are typically found attached to hair in the pubic area, sometimes they are also found on coarse hair elsewhere on the body (for example, [[eyebrow]]s, [[eyelashes]], [[beard]], [[moustache]], [[chest]], [[axilla|armpits]], etc.). They do not generally occur on the finer hair of the scalp.<ref name="service"/><ref name=1a>{{cite journal|last=Nuttall|first=GHF|title=The biology of Phthirus pubis|journal=Parasitology|year=1918|volume=10|issue=3|pages=383–405|doi=10.1017/s0031182000003954|url=https://zenodo.org/record/1428632}}</ref> Crab lice attach to pubic hair that is thicker than other body hair because their claws are adapted to the specific diameter of pubic hair and other thick hairs of the body.<ref name=":1" /> Crab louse infestations ([[Pediculosis pubis|pthiriasis]]) are usually spread through sexual contact and are most common in adults.<ref name=":1">{{Cite book|title=Williams gynecology|date=2012|publisher=McGraw-Hill Medical |author=Hoffman, Barbara L. |author2=Williams, J. Whitridge |isbn=9780071716727|edition=2nd|location=New York|oclc=779244257}}</ref><ref name="cdc1"/><ref name="cdc2"/> The crab louse can travel up to {{convert|25|cm|in|0|abbr=on}} on the body. Crab louse infestation is found worldwide and occurs in all races and ethnic groups and in all [[Socioeconomic status|socio-economic levels]]. Occasionally they may be also transmitted by close personal contact or contact with articles such as clothing, bed linen, and towels that have been used by an infested person.<ref name="cdc3"/><ref name="cdc4">{{Cite web|url=https://www.cdc.gov/lice/about/pubic-lice.html |title=About Pubic "Crab" Lice  |website=[[Centers for Disease Control and Prevention]] |language=en-us |access-date=2024-10-13 |date=2024-06-04}}{{PD-notice}}</ref>

Crab lice found on the head or eyelashes of children may be an indication of sexual exposure or abuse.<ref name="Klaus et al. 1994">{{cite journal |vauthors=Klaus S, Shvil Y, Mumcuoglu KY |title= Generalized infestation of a 3 1/2-year-old girl with the pubic louse |journal=Pediatric Dermatology |year=1994 |volume=11 |issue=1| pages=26–8| doi=10.1111/j.1525-1470.1994.tb00068.x|pmid= 8170844 |s2cid= 5989980 }}</ref> Symptoms of crab louse infestation in the pubic area include itching, redness and inflammation. Crab lice are not known to transmit disease;{{cn|date=April 2021}} however, secondary [[Pathogenic bacteria|bacterial infection]] can occur from scratching of the skin.

Crab louse infestation can be diagnosed by identifying the presence of active stages of the louse, as well as of eggs (nits) on the pubic hair and other hairs of the body. When infestation is diagnosed, other family members and contact persons should also be examined. A magnifying glass or [[Dermatoscopy|dermoscope]] could be used for better identification.<ref name=":1" />

== References ==
{{Reflist|2}}

== External links ==
{{Commons category|Pthirus pubis}}
* {{MedlinePlusEncyclopedia|000841|Pubic lice}}

{{STD/STI}}
{{Human lice}}
{{Arthropod infestations}}
{{Taxonbar|from=Q381271}}
{{Authority control}}

{{DEFAULTSORT:Crab louse}}
[[Category:Ectoparasites]]
[[Category:Insects described in 1758]]
[[Category:Lice]]
[[Category:Parasitic arthropods of humans]]
[[Category:Parasitic infestations, stings, and bites of the skin]]
[[Category:Pubic hair]]
[[Category:Sexually transmitted diseases and infections]]
[[Category:Taxa named by Carl Linnaeus]]