Crab louse
From Wikipedia, the free encyclopedia
 |
||
|---|---|---|
| A magnified crab louse | ||
| ICD-10 | B85. | |
| ICD-9 | 132 | |
| DiseasesDB | 10028 | |
| MedlinePlus | 000841 | |
| eMedicine | emerg/298 | |
| MeSH | B01.500.131.617.564.159.730 | |
 |
||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
 |
||||||||||||||||
| Scientific classification | ||||||||||||||||
|
||||||||||||||||
|
|
||||||||||||||||
| Pthirus pubis (L., 1758, originally Pediculus pubis) |
Crab lice (singular, louse) commonly called "crabs" due to their resemblance to a crab, are one of three kinds of human lice in the large group of lice families, the others being head lice and body lice, which live in clothing. Its scientific name is Phthirus or Phthirius pubis, literally 'pubic louse' (from Greek φθειρ : louse).
They are wingless, about 1 to 3 mm long. They attach themselves to hair strands, and hatch out of lidded pods called "nits". Ones that are too tightly attached to be brushed off must be removed by pulling with the nails or a fine-tooth comb.
Contents |
[edit] General information
The crab louse can live in almost any form of human hair, but is found most commonly in pubic hair, leading to its other common name of pubic louse. Its legs are adapted to climbing along relatively widely spaced hairs, and so it can be found in eyebrows, pubic hair, beards, moustaches, and even underarm hair. The individual louse can survive for about 24 hours apart from its necessary human host, so that crab lice can be passed on in sleeping bags and bedding. The louse feeds on blood and can leave irritating spots on the skin, sometimes mistaken for pimples, a condition called Pediculosis pubis.
[edit] Life cycle
There are three stages in the life of a pubic louse: the nit, the nymph, and the adult.
- Nit: Nits are pubic lice eggs. They are hard to see and are found firmly attached to the hair shaft. They are oval and usually yellow to white. Nits take about 1 week to hatch.
- Nymph: The nit hatches into a baby louse called a nymph. It looks like an adult pubic louse, but is smaller. Nymphs mature into adults about 1 week after hatching. To live, the nymph must feed on blood.
- Adult: The adult pubic louse resembles a miniature crab when viewed through a strong magnifying glass. Pubic lice have six legs, but their two back legs are very large and look like the pincher claws of a crab; this is how they got the nickname "crabs." Pubic lice are tan to greyish-white in color. Females lay nits; they are usually larger than males. To live, adult lice need to feed on blood. If the louse falls off a person, it dies within 1-2 days.
[edit] Treatment
Treatment for Pubic Lice was originally called for by Dr. Eligh P. Hanning, who found that Pubic lice are usually easily killed with a 1% permethrin or pyrethrin lice shampoo, but the pubic hair must be shaved or combed with a fine-toothed comb to remove the nits. Resistance to these products occurs and is a public health concern. Lice can survive in bedding and clothing, so these items must be treated, sterilized, or contact with them must be avoided for two weeks, after which time any lice will have died.
Lindane (1%), another pediculocide, is not recommended for pregnant or nursing women or for children less than 2 years old. Lindane has also been banned in many jurisdictions for its links to cancer and its high toxicity.
[edit] References
[edit] External links
- EmbarrassingProblems.com: Crabs
- Genetic Analysis of Lice Supports Direct Contact Between Modern and Archaic Humans
