Crab louse
Template:Short description Template:About Template:Pp-move-indef Template:Pp-semi-indef Template:Speciesbox The crab louse or pubic louse (Pthirus pubis) is an insect that is an obligate ectoparasite of humans, feeding exclusively on blood.<ref name="Bolognia">Template:Cite book</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 perianal area, the general body hair, and the eyelashes (in children).<ref name="cdc1">{{#invoke:citation/CS1|citation |CitationClass=web }}Template:PD-notice</ref><ref name="cdc2">{{#invoke:citation/CS1|citation |CitationClass=web }}Template:PD-notice</ref>
Humans are the only known hosts of the crab louse, although a closely related species, Pthirus gorillae, infects gorillas. The human parasite is thought to have diverged from Pthirus gorillae approximately 3.3 million years ago.<ref>Template:Cite journal</ref> It is more distantly related to the genus Pediculus, which contains the human head and body lice and lice that affect chimpanzees and bonobos.
DescriptionEdit
An adult crab louse is about 1.3–2 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">Template:Cite book</ref>
Life cycleEdit
The eggs of the crab louse are laid usually on the coarse hairs of the genital and 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 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 sexual contact, although fomites (bedding, clothing) may play a minor role in their transmission.<ref name="cdc3">{{#invoke:citation/CS1|citation |CitationClass=web }}Template:PD-notice</ref>
Infestation of humansEdit
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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 itching, 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.Template:Citation needed
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">Template:Cite journal</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>Template:Cite journal</ref>
It has been suggested that an increasing percentage of humans removing their pubic hair, especially in women, has led to reduced crab louse populations in some parts of the world.<ref>Template:Cite journal</ref><ref>Bloomberg: Brazilian bikini waxes make crab lice endangered species, published 13 January 2013, retrieved 14 January 2013</ref>
While crab lice are not known to transmit disease, the possibility has been raised they may be a vector for Bartonella spp. and Acinetobacter spp which might require further study.<ref name="l3582">Template:Cite journal</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, eyebrows, eyelashes, beard, moustache, chest, armpits, etc.). They do not generally occur on the finer hair of the scalp.<ref name="service"/><ref name=1a>Template:Cite journal</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 (pthiriasis) are usually spread through sexual contact and are most common in adults.<ref name=":1">Template:Cite book</ref><ref name="cdc1"/><ref name="cdc2"/> The crab louse can travel up to Template:Convert on the body. Crab louse infestation is found worldwide and occurs in all races and ethnic groups and in all 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">{{#invoke:citation/CS1|citation |CitationClass=web }}Template: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">Template:Cite journal</ref> Symptoms of crab louse infestation in the pubic area include itching, redness and inflammation. Crab lice are not known to transmit disease;Template:Cn however, secondary 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 dermoscope could be used for better identification.<ref name=":1" />
ReferencesEdit
External linksEdit
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