Body lice

Overview
Body lice are parasitic insects that live on the body and in the clothing or bedding of infested humans.

Related Key Words and Synonyms: Pediculosis

Epidemiology and Demographics
Body lice are found on the body and on clothing or bedding used by infested people; lice eggs are lain in the seams of clothing or on bedding. Occasionally eggs are attached to body hair. Body lice are spread directly through contact with a person who has body lice, or indirectly through shared clothing, beds, bed linens, or towels.

Lice found on the hair and head are not body lice; they are head lice.

Worldwide:

Infestation is common, found worldwide, and affects people of all races. Body lice infestations spread rapidly under crowded conditions where hygiene is poor and there is frequent contact among people.

United States:

Body lice are found only in homeless, transient populations who don't have access to changes of clothes or bath. Infestation is unlikely to persist on anyone who bathes regularly and who regularly has access to freshly laundered clothing and bedding.

Pathophysiology & Etiology
Etiologic agent

Pediculus humanus humanus (the body louse) is indistinguishable in appearance from Pediculus humanus capitus (the head louse) and under laboratory conditions they will interbreed. In their natural state, however, the two subspecies do not interbreed and occupy different habitats. In particular, body lice have evolved to attach their eggs to clothes, whereas head lice attach their eggs to the base of hairs.

Body lice are a nuisance in themselves and cause intense itching. They are however, also vectors (transmitters) of other diseases such as epidemic typhus.

Epidemics of typhus and louse-borne relapsing fever have been caused by body lice. Though typhus is no longer widespread, epidemics still occur during times of war, civil unrest, natural disasters, in refugee camps, and prisons where people live crowded together in unsanitary conditions. Typhus still exists in places where climate, chronic poverty, and social customs prevent regular changes and laundering of clothing.

Pathophysiology

There are three forms of body lice: the egg (sometimes called a nit), the nymph, and the adult.

Nit: Nits are body lice eggs. They are generally easy to see in the seams of clothing, particularly around the waistline and under armpits. They are about the size of the mark at the end of this arrow. Nits may also be attached to body hair. They are oval and usually yellow to white. Nits may take 30 days to hatch.

Nymph: The egg hatches into a baby louse called a nymph. It looks like an adult body louse, but is smaller. Nymphs mature into adults about 7 days after hatching. To live, the nymph must feed on blood.

Adult: The adult body louse is about the size of a sesame seed, has 6 legs, and is tan to greyish-white. Females lay eggs. To live, adult lice need to feed on blood. If the louse falls off of a person, it dies within 10 days.

Diagnosis
By looking closely in the seams of clothing and on the body for eggs and for crawling lice. Diagnosis should be made by a health care provider if you are unsure about infestation.

History and Symptoms
Itching and rash are common; both are your body's allergic reaction to the lice bite. Long-term body lice infestations may lead to thickening and discoloration of the skin, particularly around the waist, groin, and upper thighs. Sores on the body may be caused by scratching. These sores can sometimes become infected with bacteria or fungi.

Treatment
Lice infestations are generally treated by giving the infested person a clean change of clothes, a shower, and by laundering all worn clothing, bed linens, and towels. When laundering items, use the hot cycle (130°F) of the washing machine. Set the dryer to the hot cycle to dry items. Additionally, a 1% permethrin or pyrethrin lice shampoo, (also called pediculicide peh-DICK-you-luh-side), may be applied to the body. Medication should be applied exactly as directed on the bottle or by your physician.

Acknowledgements
The content on this page was first contributed by: C. Michael Gibson, M.S., M.D.