Overview

Brief Summary

The Pubic (or Crab) Louse (Pthirus pubis, often incorrectly spelled Phthirus pubis) is an insect in the Order Psocodea (parasitic lice, formerly Order Phthiraptera, plus bark lice, formerly Order Psocoptera). Pubic Lice are ectoparasites with humans as the only host.They are found throughout the world.

Pubic lice have three stages: egg, nymph and adult. Eggs (nits) are laid on a hair shaft. Females will lay approximately 30 eggs during their 3-4 week life span. Eggs hatch after about a week and become nymphs, which look like smaller versions of the adults. The nymphs undergo three molts before becoming adults. Adults are 1.5-2.0 mm long and flattened. They are much broader in comparison to head and body lice. Adults are found only on the human host and require human blood to survive. If adults are forced off the host, they will die within 24-48 hours without a blood feeding. Pubic lice are transmitted from person to person most commonly via sexual contact, although fomites (bedding, clothing) may play a minor role in their transmission.

(Centers for Disease Control Parasites and Health website)

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Distribution

Geographic Range

Pthirus pubis is a host specific louse found throughout the world on humans.

Biogeographic Regions: nearctic ; palearctic ; oriental ; ethiopian ; neotropical ; australian ; oceanic islands

Other Geographic Terms: cosmopolitan

  • Burkhart, C., C. Burkhart. MAR 1999. Return of the silent merengue:The crab louse. Infect Med., 16 (3): 182.
  • Scott, G., K. Radcliff, I. Ahmed-Jushuf. AUG 1999. National guideline for the management of Phthirus Pubis infestation. SEX TRANSM INFECT, 75: Suppl. 1: S78-S79.
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Physical Description

Morphology

Physical Description

Smaller than Pediculus humanus (head and body lice), gray "crab" lice are 1.25 to 2 mm long. Pthirus pubis has an oval body shape and is wider than it is long and these lice are given the nickname "crabs" from their shape and chelate tarsi. These lice also have small heads relative to their body size, simple eyes, and short antennae. The lice have six legs, each of which terminate with a tarsal claw. The claws on the 2nd and 3rd pairs of legs are huge compared to those on the pair of legs closest to the head, which are smaller and thinner. Pthirus pubis also has another modification of the claw region, which is actually an extension of the tibia, called the thumb of the tibia which allows it to grasp the flattened hairs of the pubic region of humans. Another distinguishing feature is the four pairs of tubercles, which stick out on each side of the animal's abdomen. Lice breathe through spiracles at the ends of these para-tergal sclerites leading to the tracheal system.

Range length: 1.25 to 2 mm.

Other Physical Features: ectothermic ; heterothermic ; bilateral symmetry

Sexual Dimorphism: sexes alike

  • Opaneye, A., D. Jayaweera. FEB 1993. Pediculosis pubis- A Surrogate Marker for Sexually-Transmitted Diseases. J ROY SOC HEALTH, 113 (1): 6-7.
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Ecology

Habitat

Pthirus pubis lays its eggs on coarse body hair, especially in hair associated with the pubic regions, but also in the anal region, armpits, thighs, abdomen and will even infect eyelashes and beards. These regions have flattened hairs, which the claws of P. pubis are highly modified to grasp. These lice are mostly found in unsanitary or overcrowded conditions of human hosts.

Habitat Regions: temperate ; tropical ; polar ; terrestrial

Other Habitat Features: urban ; suburban ; agricultural

  • Kremer, M., C. Ball. NOV 1997. Why doesn't the crab-louse (Phthirus pubis) invade the scalp?. ANN DERMATOL VENER, 124 (11): 817-818.
  • Mori, R., M. Hayakawa, K. Koide. 1978. 3 Cases of infection of the eyelashes by Crab Louse. FOLIA OPHTHALMOLOGY JPN, 29 (12): 1890-1892.
  • Roberts, L., J. Janovy. 2000. Foundations of Parasitology 2nd ed.. McGraw-Hill Higher Education.
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Trophic Strategy

Food Habits

Pubic lice feed on human blood and will die within 24 hours without having a human blood meal. Species in the order Anoplura, to which P. pubis belongs, have a highly modified feeding mechanism. They lack mandibles like all other types of lice and they have a fascicle made of four stylets which they use to feed on the blood of their hosts. The haustellum derived from the labrum supports the fascicle. Two of the stylets derived from the maxillae lock together to form a food channel. A single hollow stylet derived from the hypopharynx connects with the salivary duct and conveys salivary materials into the wound. And a large flattened stylet derived form the labium cuts into tissue with a serrated tip and serves as a guide for the other stylets. The cibarium and pharynx in the head serve as a two-chambered pump, sucking material in through the mouth and passing it on to the esophagus.

Animal Foods: blood

Primary Diet: carnivore (Sanguivore )

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Associations

Animal / parasite / ectoparasite / blood sucker
Pthirus pubis sucks the blood of pubic hair of Homo sapiens
Other: sole host/prey

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Ecosystem Roles

Pthirus pubis is an obligate ectoparasite of humans.

Ecosystem Impact: parasite

Species Used as Host:

  • humans

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Life History and Behavior

Behavior

Communication and Perception

Presumably, lice can tell when they have hit a blood vessel when beginning to feed by sensing chemicals released at the site of the wound. Also, lice have short antennae with chemoreceptors and tactile hairs, and some, such as P. pubis, have simple eyes. No information is available on how these lice communicate with one another.

Perception Channels: visual ; tactile ; chemical

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Life Cycle

Development

All lice exhibit hemimetabolous development, consisting of three life stages: egg, nymph, and adult. The eggs of P. pubis hatch in six to eight days and the young lice then pass through three nymphal stages, lasting a total of 23 days, before becoming adults.

Development - Life Cycle: metamorphosis

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Life Expectancy

Lifespan/Longevity

These lice normally live for a little less than a month, dying soon after reproducing. However, when separated from a host, they live less than 24 hours.

Average lifespan

Status: wild:
1 months.

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Reproduction

No information is available on the mating system of these lice.

These lice reach sexual maturity about 23 days after hatching from eggs. Reproduction is sexual, with the male P. pubis inserting his aedeagus (male reproductive intromittant organ) into the female genital opening and deposting sperm. Females lay approximately 30 eggs in a lifetime and when cemented to hairs, these are called nits.

Breeding season: These lice breed year-round.

Range gestation period: 6 to 8 days.

Average age at sexual or reproductive maturity (female): 23 days.

Average age at sexual or reproductive maturity (male): 23 days.

Key Reproductive Features: iteroparous ; year-round breeding ; gonochoric/gonochoristic/dioecious (sexes separate); sexual ; fertilization (Internal ); oviparous

Female lice provide nutrients to their eggs before laying them and then abandon them.

Parental Investment: pre-fertilization (Provisioning, Protecting: Female)

  • Burkhart, C., C. Burkhart. MAR 1999. Return of the silent merengue:The crab louse. Infect Med., 16 (3): 182.
  • Roberts, L., J. Janovy. 2000. Foundations of Parasitology 2nd ed.. McGraw-Hill Higher Education.
  • Scott, G., K. Radcliff, I. Ahmed-Jushuf. AUG 1999. National guideline for the management of Phthirus Pubis infestation. SEX TRANSM INFECT, 75: Suppl. 1: S78-S79.
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Molecular Biology and Genetics

Molecular Biology

Barcode data: Pthirus pubis

The following is a representative barcode sequence, the centroid of all available sequences for this species.


There are 7 barcode sequences available from BOLD and GenBank.  Below is a sequence of the barcode region Cytochrome oxidase subunit 1 (COI or COX1) from a member of the species.  See the BOLD taxonomy browser for more complete information about this specimen and other sequences.

TTAGTTCCTTTA---TTTTTAGGTGCTCCTGACATGGCTTTCCCCCGGATGAACAATATAAGCTATTGGCTGATTATGCCCTCTGGGGTTCTGTTAATTGCGAGTTCAATAATCCAAGGTGGAACAGGTACTGGCTGGACTATTTATCCTCCGCTAAGTTCTTTAGAAGGCCAACCTTCTTTATCAGTGGATTTT---ACCATCTTTAGCCTCCATTTAGCTGGAGTAAGTTCTATTTTAGGCTCAGTAAATTTTATTAGGACAATTTTAAATATATGACCTTCTAGGTTAAAGATTTACCGGTTACCTTTGTTCTGCTGGTCTGTCTTAATCACGGCCTTTTTGCTTCTACTCTCTTTACCTGTACTTGCGGGT---GCTATCACTATGCTACTATTAGATCGGAATTTTAATTGTTCTTTTTTTGACCCTCTAGGTGGAGGTGATCCTGTTCTTTACCAGCATCTTTTTTGGTTTTTTGGTCATCCTGAGGTTTATATCTTGATCTTACCTGGGTTTGGATTGATCTCTCATATGGTTGTTGACTTGAGAGGTAAGAAA---GAAGTCTTTGGTTCATTAGGAATAATCTACGCTATAGTATCGATTGGTGTTCTAGGGTTTGTTGTTTGAGCCCACCACATGTTCACTGTTGGTCTAGATGTAGATAGACGTGCTTACTTTACTAGAGCTACTATGACCATTGCTATTCCAACGGGAGTAAAAGTCTTTAGCTGATTAGGT---ACTCTATTTGGCCCT---AAACTTCACTTAAGAGTGAGGTTGCAGTGGTCTCTGGGATTCATCTTTTTATTTACTGTTGGAGGCCTGACAGGGATTATTCTATCTAACTCGTCAGTTGACGTTCTTCTT
-- end --

Download FASTA File
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Statistics of barcoding coverage: Pthirus pubis

Barcode of Life Data Systems (BOLDS) Stats
Public Records: 7
Specimens with Barcodes: 7
Species With Barcodes: 1
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Relevance to Humans and Ecosystems

Benefits

Economic Importance for Humans: Negative

Infestation of P. pubis is a sexually transmitted condition causing serious itching to its victims. Irritation is increased in the area with host scratching and the area can often become scabby with oozing lesions. Asymptomatic individuals may discover nits or lice on pubic hair, or black specks on underpants. Characteristic small blue-gray macules known as maculae caeruleae may appear at bitten sites. Complications including excoriations, secondary bacterial infections, and eczematization may ensue.

Pthirus pubis thrives in unsanitary, overcrowded living conditions and historically has been common in military, refugee, and concentration camps, prisons, and overcrowded city dwellings. Overcrowding favors P. pubis because it can migrate between hosts easily and is not always contracted through sexual contact.

Unlike body lice (Pediculus humanus), pubic lice are not known to spread typhus.

Negative Impacts: injures humans (bites or stings)

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Economic Importance for Humans: Positive

There is often a strong correlation between the infection of Pthirus pubis in the eyelashes and individuals having other sexually transmitted diseases. Therefore, Pthirus pubis can sometimes be used as an indicator of more serious problems.

  • Skinner, C., N. Viswalingam, B. Goh. DEC 1994. Phthirus pubis infestation of the eyelids: A marker for sexually transmitted diseases. INT JOURNAL STD AIDS, 6 (6): 451-452.
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Wikipedia

Crab louse

This article is about the animal. For the disease known as crab lice, see Pediculosis pubis.
Pubic lice on eyelashes

The crab louse (Pthirus pubis, frequently misspelled as Phthirus pubis), also known as the pubic louse, is an insect that is an obligate ectoparasite of humans.[1] It is typically found in pubic hair, but may also live on other areas with coarse hair, including the eyelashes. They cannot jump, and feed exclusively on blood. Humans are the only known hosts of this parasite, although a closely related species, Pthirus gorillae, infects gorilla populations. The species passed to humans 3.3 million years ago.[2]

Description[edit]

An adult crab louse is about 1.3–2 mm long (considerably 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 back two pairs of legs of a crab louse are much thicker than the front legs and are equipped with large claws.[3]

Life cycle[edit]

The eggs of the crab louse are laid usually on the coarse hairs of the genital and perianal regions of the human body. Crab lice may also be found on other areas of the body that have coarse and relatively sparse coverings of hair, such as the beard, moustache, eyelashes, underneath the arms. They do not generally occur on the finer hair of the scalp.[3][4]

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.[3] Crab lice feed exclusively on blood, and take a blood meal 4–5 times daily.

Infestation of humans[edit]

Main article: Pediculosis pubis

Infestations of crab lice are known as pediculosis pubis or phthiriasis pubis (which, unlike the generic name of the louse, is spelled with a phth). Infestation of the eyelashes is referred to as pediculosis ciliaris or phthiriasis palpebrarum.[5]

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 days.

Current worldwide prevalence has been estimated at 2% of the human population, but accurate numbers are difficult to gauge because crab lice infestations are not considered a reportable condition by many governments, and many cases are self-treated or treated discreetly by primary physicians.[6]

Crab lice usually infect a new host only by close contact between individuals, usually through sexual intercourse. Adults are more frequently infested than children. Non-sexual transmissions may occur among family and roommates through the use of shared towels, clothing, beds or closets. They can only survive a short time away from the warmth and humidity of the human body.

It has recently been suggested that an increasing percentage of humans removing their pubic hair has led to reduced crab louse populations in some parts of the world.[7][8] Because the World Health Organization and other authorities do not record statistics for pubic louse infestation, there are virtually no hard data to support this supposition.

References[edit]

  1. ^ Rapini, Ronald P.; Bolognia, Jean L.; Jorizzo, Joseph L. (2007). Dermatology: 2-Volume Set. St. Louis: Mosby. ISBN 1-4160-2999-0. 
  2. ^ Weiss RA (10 February 2009). "Apes, lice and prehistory". J Biol 8 (2): 20. doi:10.1186/jbiol114. PMC 2687769. PMID 19232074. 
  3. ^ a b c Service, Mike (2012). Medical Entomology for Students (5th ed.). Cambridge: Cambridge University Press. ISBN 978-1-107-66818-8. 
  4. ^ Nuttall, GHF (1918). "The biology of Phthirus pubis". Parasitology 10: 383–405. 
  5. ^ 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
  6. ^ 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. 
  7. ^ 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.  edit
  8. ^ Bloomberg: Brazilian bikini waxes make crab lice endangered species, published 13 January 2013, retrieved 14 January 2013
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