Pediculosis pubis (also known as "crabs" and "pubic lice") 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.The main symptom is an intense itch in the groin, particularly at night. There may be some grey-blue discolouration at the feeding site, and eggs and lice may be visible. Scratch marks, crusting and scarring may be seen, and there may be signs of secondary bacterial infection.Diagnosis is by visualising the nits or live lice, either directly or with a magnifying glass. Investigations for other sexually transmitted infections (STIs) are usually performed.First line treatment usually contains permethrin and is available over the counter. Two rounds of treatment at least a week apart are usually required to kill newly hatched nymphs. Washing bedding and clothing in hot water kills the lice, and transmission can be prevented by avoiding sexual contact until no signs of infestation exist. Eggs may be removed by combing pubic hair with a comb dipped in vinegar. Sexual partners should be evaluated and treated.Infestation with pubic lice is found in all parts of the world and occurs in all ethnic groups and all levels of society. Worldwide, the condition affects about 2% of the population.
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. 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. Diagnosis
Diagnosis is made by carefully looking at the pubic hair for nits, young lice and adult lice. Lice and nits can be removed either with forceps or by cutting the infested hair with scissors (with the exception of an infestation of the eye area). A magnifying glass, dermatoscope or a stereo-microscope can be used for identification. Testing for other sexually transmitted infections is recommended in those who are infested with pubic lice. Treatment
Pubic lice can be treated at home. Available treatments may vary from country to country and include mainly permethrin-containing creams and lotions applied to cool dry skin.Treatment with medication is combined with combing pubic hair with a fine-toothed comb after applying vinegar directly to skin or dipping the comb in vinegar, to remove nits. It is recommended to wash bedding, clothing and towels in hot water or preferably in a washing machine at 50°C or higher. When this is not possible, the clothing can be stored in a sealed plastic bag for at least three days. Re-infestation can be prevented by wearing clean underwear at the start of treatment and after completing treatment. Shaving the affected hair is not essential.