Crab louse

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Crab louse
Crab louse (251 23) Female, from a human host.jpg
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Psocodea
Family: Pthiridae
Genus: Pthirus
Species:
P. pubis
Binomial name
Pthirus pubis
Synonyms
  • Pediculus pubisLinnaeus, 1758
  • Phthirus pubis Leach, 1817 [1]

The crab louse or pubic louse (Pthirus pubis) is an insect that is an obligate ectoparasite of humans, feeding exclusively on blood. [2] 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 entire body (in men), and the eyelashes (in children). [3] [4]

Contents

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. [5] It is more distantly related to the genus Pediculus , which contains the human head and body lice and lice that affect chimpanzees and bonobos.

Description

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. [6]

Life cycle

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. [6] 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. [7]

Infestation of humans

Crab lice on eyelashes Pubic lice on eye-lashes.jpg
Crab lice on eyelashes
Live louse magnified about 10x
Live louse magnified about 10x

Infestation of the eyelashes is referred to as pediculosis ciliaris or phthiriasis palpebrarum. [8]

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.[ citation needed ]

Crab louse egg on human body hair Crab egg.jpg
Crab louse egg on human body hair

Current worldwide prevalence has been estimated at 2% of the human population, but accurate numbers are difficult to gauge because crab louse infestations are not considered a reportable condition by many health authorities, and many cases are self-treated or treated discreetly by physicians. [9]

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. [10] [11]

Crab lice Crab Lice CDC.png
Crab lice

Crab lice are not known to transmit disease. 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. [6] [12] 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. [13] Crab louse infestations (pthiriasis) are usually spread through sexual contact and are most common in adults. [13] [3] [4] The crab louse can travel up to 25 cm (10 in) 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. [7] [14]

Crab lice found on the head or eyelashes of children may be an indication of sexual exposure or abuse. [15] Symptoms of crab louse infestation in the pubic area include itching, redness and inflammation. Crab lice are not known to transmit disease; however, secondary bacterial infection can occur from scratching of the skin.[ citation needed ]

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. [13]

Related Research Articles

<span class="mw-page-title-main">Louse</span> Order of insects

Louse is the common name for any member of the clade Phthiraptera, which contains nearly 5,000 species of wingless parasitic insects. Phthiraptera has variously been recognized as an order, infraorder, or a parvorder, as a result of developments in phylogenetic research.

<span class="mw-page-title-main">Sucking louse</span> Suborder of insects

Sucking lice have around 500 species and represent the smaller of the two traditional superfamilies of lice. As opposed to the paraphyletic chewing lice, which are now divided among three suborders, the sucking lice are monophyletic.

<span class="mw-page-title-main">Trichuriasis</span> Infection by Trichuris trichiura (whipworm)

Trichuriasis, also known as whipworm infection, is an infection by the parasitic worm Trichuris trichiura (whipworm). If infection is only with a few worms, there are often no symptoms. In those who are infected with many worms, there may be abdominal pain, fatigue and diarrhea. The diarrhea sometimes contains blood. Infections in children may cause poor intellectual and physical development. Low red blood cell levels may occur due to loss of blood.

<span class="mw-page-title-main">Pubic hair</span> Hair in the human genital area

Pubic hair is terminal body hair that is found in the genital area of adolescent and adult humans. The hair is located on and around the sex organs and sometimes at the top of the inside of the thighs. In the pubic region around the pubis bone and the mons pubis that covers it, it is known as a pubic patch. Pubic hair is also found on the scrotum and base of the penile shaft in the male and on the vulva in the female.

<span class="mw-page-title-main">Pediculosis</span> Medical condition

Pediculosis is an infestation of lice from the sub-order Anoplura, family Pediculidae. Accordingly, the infestation with head lice is named pediculosis capitis, while this with body lice, pediculosis corporis. Although pediculosis in humans may properly refer to lice infestation of any part of the body, the term is sometimes used loosely to refer to pediculosis capitis, the infestation of the human head with the specific head louse.

<span class="mw-page-title-main">Head louse</span> Insect parasite of humans

The head louse is an obligate ectoparasite of humans. Head lice are wingless insects that spend their entire lives on the human scalp and feed exclusively on human blood. Humans are the only known hosts of this specific parasite, while chimpanzees and bonobos host a closely related species, Pediculus schaeffi. Other species of lice infest most orders of mammals and all orders of birds.

A crab is a water-dwelling creature, a decapod crustacean of the infraorder Brachyura. A related common meaning is crab meat.

<span class="mw-page-title-main">Treatment of human lice</span>

The treatment of human lice is the removal of head lice parasites from human hair. It has been debated and studied for centuries. However, the number of cases of human louse infestations has increased worldwide since the mid-1960s, reaching hundreds of millions annually. There is no product or method that assures 100% destruction of the eggs and hatched lice after a single treatment. However, there are a number of treatment modalities that can be employed with varying degrees of success. These methods include chemical treatments, natural products, combs, shaving, hot air, and silicone-based lotions.

<span class="mw-page-title-main">Body louse</span> Subspecies of insect

The body louse is a hematophagic ectoparasite louse that infests humans. It is one of three lice which infest humans, the other two being the head louse, and the crab louse or pubic louse.

A louse is a wingless insect.

<span class="mw-page-title-main">Head lice infestation</span> Medical condition

Head lice infestation, also known as pediculosis capitis, is the infection of the head hair and scalp by the head louse. Itching from lice bites is common. During a person's first infection, the itch may not develop for up to six weeks. If a person is infected again, symptoms may begin much more quickly. The itch may cause problems with sleeping. Generally, however, it is not a serious condition. While head lice appear to spread some other diseases in Africa, they do not appear to do so in Europe or North America.

<span class="mw-page-title-main">Sexually transmitted infection</span> Infection transmitted through human sexual behavior

A sexually transmitted infection (STI), also referred to as a sexually transmitted disease (STD) and the older term venereal disease (VD), is an infection that is spread by sexual activity, especially vaginal intercourse, anal sex, oral sex, or sometimes manual sex. STIs often do not initially cause symptoms, which results in a risk of passing the infection on to others. Symptoms and signs of STIs may include vaginal discharge, penile discharge, ulcers on or around the genitals, and pelvic pain. Some STIs can cause infertility.

<span class="mw-page-title-main">No nit policy</span> Public health policy

No nit policy is a public health policy implemented by some education authorities to prevent the transmission of head lice infestation. The "no nit" policy requires the sending home and barring of all children who have nits on their hair from controlled settings such as school, summer camp or day care facilities. The CDC, American Academy of Pediatrics (AAP) and the National Association of School Nurses (NASN) advocate that "no-nit" policies should be discontinued, due in part because nits, the eggs or empty egg shells, are not transmissible and the burden of unnecessary absenteeism to the students, families and communities far outweighs the risks associated with head lice. Proponents of the no-nit policy counter that only a consistently nit-free child can be reliably shown to be infestation-free. That is, the presence of nits serves as a proxy for infestation status. Proponents argue that such a proxy is necessary because lice screening is prone to false negative conclusions.

An ectoparasitic infestation is a parasitic disease caused by organisms that live primarily on the surface of the host.

<span class="mw-page-title-main">Pediculosis corporis</span> Medical condition

Pediculosis corporis or Vagabond's disease is a cutaneous condition caused by body lice that lay their eggs in the seams of clothing.

<span class="mw-page-title-main">Vulva</span> External genitalia of the female mammal

In mammals, the vulva consists of the external female genitalia. The human vulva includes the mons pubis, labia majora, labia minora, clitoris, vestibular bulbs, vulval vestibule, urinary meatus, the vaginal opening, hymen, and Bartholin's and Skene's vestibular glands. The urinary meatus is also included as it opens into the vulval vestibule. Other features of the vulva include the pudendal cleft, sebaceous glands, the urogenital triangle, and pubic hair. The vulva includes the entrance to the vagina, which leads to the uterus, and provides a double layer of protection for this by the folds of the outer and inner labia. Pelvic floor muscles support the structures of the vulva. Other muscles of the urogenital triangle also give support.

<span class="mw-page-title-main">Pediculosis pubis</span> Infestation by the pubic louse

Pediculosis pubis is an infestation by the pubic louse, Pthirus pubis, a wingless insect which feeds on blood and lays its eggs (nits) on mainly pubic hair. Less commonly, hair near the anus, armpit, beard, eyebrows, moustache, and eyelashes may be involved. It is usually acquired during sex, but can be spread via bedding, clothing and towels, and is more common in crowded conditions where there is close contact between people.

<i>Pthirus gorillae</i> Species of louse

Pthirus gorillae or gorilla louse is a species of parasitic sucking louse that afflicts gorillas. It is found in the African continent, specifically in Rwanda and Democratic Republic of the Congo. P. gorillae and P. pubis are the only known species that belong to the genus Pthirus, often incorrectly spelled as Phthirus. It is suggested that it is transmitted among its hosts by social grooming, shared bedding and sexual contact.

<i>Pthirus</i> Genus of lice

Pthirus is a genus of lice. There are only two extant species, and they are the sole known members of the family Pthiridae. Pthirus gorillae infests gorillas, and Pthirus pubis afflicts humans, and is commonly known as the crab louse or pubic louse. The two species diverged some 3.3 million years ago.

<i>Haematopinus suis</i> Species of louse

Haematopinus suis, the hog louse, is one of the largest members of the louse suborder Anoplura, which consists of sucking lice that commonly afflict a number of mammals. H. suis is found almost solely on the skin surface of swine, and takes several blood meals a day from its host. H. suis has large claws that enable it to grasp a hog's hair and move around its body. It is easily seen without magnification, being 5–6 millimetres (0.20–0.24 in) long. H. suis has a long, narrow head and long mouthparts adapted for sucking blood. It is the only louse found on swine. H. suis infestation is relatively rare in the US; a 2004 study found that about 14% of German swine farms had H. suis infestations. Due to the frequency of feeding, infected swine become severely irritated, often rubbing themselves to the point of injuring their skin and displacing body hair. Particularly afflicted hogs may become almost completely bald and, in young hogs, the resulting stress can arrest growth, a cause of concern for farmers.

References

  1. "Taxonomy of Human Lice". Phthiraptera.info. Archived from the original on April 14, 2020.
  2. Rapini, Ronald P.; Bolognia, Jean L.; Jorizzo, Joseph L. (2007). Dermatology: 2-Volume Set. St. Louis: Mosby. ISBN   978-1-4160-2999-1.
  3. 1 2 CDC (Centers for Disease Control and Prevention) (2017-05-02). "Parasites: lice". www.cdc.gov. Retrieved 2017-12-04.PD-icon.svg This article incorporates text from this source, which is in the public domain .
  4. 1 2 CDC (Centers for Disease Control and Prevention) (2017-05-02). "Parasites: pubic "crab" lice". www.cdc.gov. Retrieved 2017-12-04.PD-icon.svg This article incorporates text from this source, which is in the public domain .
  5. Weiss RA (10 February 2009). "Apes, lice and prehistory". J Biol. 8 (2): 20. doi:10.1186/jbiol114. PMC   2687769 . PMID   19232074.
  6. 1 2 3 Service, Mike (2012). Medical Entomology for Students (5th ed.). Cambridge: Cambridge University Press. ISBN   978-1-107-66818-8.
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  8. 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
  9. Anderson AL, Chaney E (February 2009). "Pubic lice (Pthirus pubis): history, biology and treatment vs. knowledge and beliefs of US college students". Int J Environ Res Public Health. 6 (2): 592–600. doi: 10.3390/ijerph6020592 . PMC   2672365 . PMID   19440402.
  10. Armstrong, N. R.; Wilson, J. D. (2006). "Did the "Brazilian" kill the pubic louse?". Sexually Transmitted Infections. 82 (3): 265–266. doi:10.1136/sti.2005.018671. PMC   2564756 . PMID   16731684.
  11. Bloomberg: Brazilian bikini waxes make crab lice endangered species, published 13 January 2013, retrieved 14 January 2013
  12. Nuttall, GHF (1918). "The biology of Phthirus pubis". Parasitology. 10 (3): 383–405. doi:10.1017/s0031182000003954.
  13. 1 2 3 Hoffman, Barbara L.; Williams, J. Whitridge (2012). Williams gynecology (2nd ed.). New York: McGraw-Hill Medical. ISBN   9780071716727. OCLC   779244257.
  14. CDC (Centers for Disease Control and Prevention) (2017-05-02). "Pubic "crab" lice: epidemiology & risk factors". www.cdc.gov. Retrieved 2017-12-04.PD-icon.svg This article incorporates text from this source, which is in the public domain .
  15. Klaus S, Shvil Y, Mumcuoglu KY (1994). "Generalized infestation of a 3 1/2-year-old girl with the pubic louse". Pediatric Dermatology. 11 (1): 26–8. doi:10.1111/j.1525-1470.1994.tb00068.x. PMID   8170844. S2CID   5989980.