Pubic lice are parasitic insects also known as crab lice (or simply crabs) that are found majorly in the pubic area of humans. They feed on blood and are only found on humans. The lice may also be in other parts of the body covered in coarse hair like eyebrows and armpits. Infestation of such lice in humans is known as phthiriasis pubis or pediculosis pubis.
Adult pubic lice look like crabs with two large front legs that look like the pincher claws of a crab. They are around 1.2 to 2 mm long and are tan to grayish-white in color. The females lay lice eggs or nits that are usually white in color and attach themselves to the hair shafts. Nits may take six to ten days to hatch. After hatching, an immature louse feeds on blood of the host and takes around two to three weeks to become an adult crab louse capable of reproducing.
Lice need blood of the host to survive and will die within a day or two of falling off from a person.
The most common mode of transmission of pubic lice is through sexual activity. Other modes include close personal contact with an infected person or sharing of towels, bedding and clothing but these are less common modes of transmission since the lice can survive for only a short period of time away from the warmth provided by the human body.
Pubic lice cannot be transferred from contact with animals.
A major symptom of infestation is itching in the genital area. In some cases, the itching may start within a short period of getting infected while in other instances, it may take longer to begin, say two to four weeks.
Other signs include appearance of lice and nets in the area. The lice may also be found in other parts of the body with coarse hair, such as armpits, beard, moustache, eyebrows or eyelashes. Lice may also be found on the head, but such lice are generally head lice and not pubic lice.
There may also be other symptoms like sores due to scratching or in a few cases, a skin reaction that may turn the skin bluish-gray.
Usually, a person with an infestation is able to identify pubic lice himself or herself by looking through coarse hair and finding a crab louse or nit in the pubic area or other suspected regions of the body. Although they are small in size, they can be easily seen with the naked eye. Pubic lice generally do not crawl around as much as head lice and usually attach themselves to a few strands of hair. Since there may only be a few, it is sometimes difficult to find them. The appearance of nits is a strong indicator of infestation even when a crawling louse cannot be spotted.
It is advisable to visit a health care practitioner in case of suspicion. Also, persons with infestation are sometimes advised to get tested for other sexually transmitted diseases.
A health care provider would typically conduct a physical examination of the genital area to look for nits that have fastened themselves to the hair shafts or for adult lice. The examiner would also look out for scratch marks or signs of infection.
In some cases, pubic lice may be found in eyelashes and the condition is known as phthiriasis palpebrarum or pediculosis ciliarum. A healthcare provider would also examine eyelashes with a strong magnifying glass to look for the lice.
It may also be noted that infection in a young child may indicate the possibility of sexual abuse although not necessarily so since pubic lice may spread through modes other than sexual contact as well.
The most common treatment is application of topical lotions or washes containing permithrin or pyrehtrins and piperonyl butoxide. These are commonly available without prescription and are considered safe to use and effective. These are generally to be applied to the pubic area and allowed to remain for a few minutes (as recommended in the label) before rinsing. After rinsing, the hair in the region is to be combed to remove the nits attached to the hair shafts. It is also advisable to wash the towels, clothing and bedding of an infected person to remove any remaining lice and nits that may be attached to these items. A second wash may be required after ten days or so if there are still any lice or nets remaining.
Another line of treatment is use of lindane shampoo that also kills lice and lice eggs. However, due to toxicity concerns, this is not a preferred mode of treatment and is not to be used by pregnant or lactating women, children under two years of age, the elderly or those with extensive dermatitis or sores where lindane is to be applied. Lindane is generally only advised for persons who are not cured using other treatments.
The sexual partners of infested persons should also be checked and treated, if required.
For infestation of the eyelashes, it is best to approach a health care provider who would typically prescribe an ophthalmic-grade petrolatum ointment that is to be applied to the eyelid margins.