Human lice are responsible for the infestations pediculosis capitis, pediculosis corporis and pediculosis pubis. Transmission is through contact with infested humans, clothing, combs or bed linen.
Pubic lice or crab lice (Phthirus pubis) are usually transmitted by sexual contact. Pubic lice typically are found attached to hair in the pubic area but sometimes are found on coarse hair elsewhere on the body for example, eyebrows, eyelashes, beard, mustache, chest and armpits.
The incubation period is between 5 days and several weeks. The female insect lives for about a month, and lays 7-10 eggs (nits) a day, which in turn hatch in about 8-10 days. The crab louse measures 3-4 mm in length and prefers axillary, eyebrow, eyelash, beard, pubic, limb and trunk hairs and lays its eggs on these hairs.
SYMPTOMS AND SIGNS
Patients who have pubic lice usually seek medical attention because of pruritus or because they notice lice or nits on their pubic hair.
The identification of adult lice or nits is diagnostic. Nits are often easier to find than lice, and resemble poppy-seeds attached to the base of the hair.
The presence of bruise-like bites (maculae ceruleae: asymptomatic, macular, blue discolourations on the trunk and thighs) or dark specks of louse faeces suggest the diagnosis of louse infestation.
A helpful technique is to fasten a piece of transparent adhesive tape to the infested areas. Lice stick to the tape, which then becomes a convenient coverslip for a microscopic slide.
- Clothing and bed linen need to be washed (i.e. machine-washed, machine-dried using the heat cycle, or dry cleaned) or removed from body contact for at least 72 hours, as lice can only survive for a short time outside the human host.
- Fumigation of bedding and living areas is not necessary.
- Permethrin 1% cream (Lyclear) or 1% lotion (Quellada) should be applied to the affected area and washed off after 20 minutes. Permethrin has activity against eggs, as it retains residual activity on the hair for 2 weeks, thereby killing any eggs that hatch after treatment. A second treatment can be given 1 week after the first, for maximum cure rate.
- Antihistamines can assist with itch, which can last for a few days after treatment.
- Eyelash involvement: Petroleum jelly application twice daily for 10 days
- If treatment has failed with the above agents, malathion 0.5% lotion (Maldison) can be tried. It is applied for 8–12 hours then washed off. Avoid in pregnancy (B2).
- Oral ivermectin has been successfully used to treat pubic lice but has only been evaluated in small studies. Currently it isn’t licensed for use in pubic lice in Australia.
- Lindane is not recommended as first-line therapy because of toxicity.
The sexual partners of patients with pediculosis pubis should be treated, where contact has occurred with the last month. Sexual contact should be avoided until patients and partners have been treated.
The content of these treatment guidelines is for information purposes only. The treatment guidelines are generic in character and should be applied to individuals only as deemed appropriate by the treating practitioner on a case by case basis. Alfred Health, through MSHC, does not accept liability to any person for the information or advice (or the use of such information or advice) which is provided through these treatment guidelines. The information contained within these treatment guidelines is provided on the basis that all persons accessing the treatment guidelines undertake responsibility for assessing the relevance and accuracy of the content and its suitability for a particular patient. Responsible use of these guidelines requires that the prescriber is familiar with contraindications and precautions relevant to the various pharmaceutical agents recommended herein.
Last Updated January 2017