Lice

Body lice are potential vectors of typhus (Section 16.2) and relapsing fever (Section 16.3), but the main worry of people is personal infestation.

Organism Pediculus humanus corporis, the body louse, P. h. capitis, the head louse and P. thirus pubis, the crab louse. Lice glue their eggs to body hairs (nits) in which they are resistant to treatment until the nymphs hatch.

Clinical features and diagnosis Intense, localized itching at the site of bite will indicate lice, which can be found and identified with a hand lens. If P. h. corporis is not on the skin, they will be amongst body hair or in the clothes.

Transmission is by close contact between people, the sharing of clothes, hats and combs. Crab lice are generally transmitted during sexual contact.

Occurrence and distribution Body lice are found worldwide in conditions of poverty or where people are forcibly driven together, such as in refugee camps. They are more common in colder regions of the world or in mountainous parts of the tropics where people huddle together to keep warm. Head lice are found both in the tropics and the colder regions, especially amongst school children.

Incubation period Eggs hatch in 10-14 days.

Period of communicability is as long as there are viable lice on the individual, up until 2 weeks after the first course of treatment. Body and head lice remain alive for up to 1 week on clothing not being worn, and nits for 1 month.

Control and prevention Washing with warm water and soap at frequent intervals is the main method of prevention. Clothes of an infected person should be boiled or insufflated with insecticide powder. The practice of pressing clothes with a hot iron might have originated as a method of controlling lice. Combs should be washed regularly and only used by one person.

Treatment is with 1% permethrin cream rinse, naturally occurring pyrethrins (from Chrysanthemum) and oral ivermectin. The treatment should be repeated after 10-14 days to kill any young lice recently hatched from nits. Shaving of heads is a rigorous and effective method of control of head lice, but not of body lice. In epidemic situations, whole communities should be treated irrespective of whether lice have been found or not (Section 16.2). Clothes and bedding can be treated with 1% malathion, 0.5% permethrin, 2% temefos (Abate), 5% iodofen-phos, 1% propoxur or 5% carbaryl.

Surveillance Parents or older siblings should carefully search through children's hair, looking for nits, if the child is found to be scratching his/her head. In situations such as refugee camps, people should be encouraged to examine their clothes and those of their children at regular intervals.

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