Body lice

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]

Synonyms and keywords: Pediculosis; Pediculus humanus humanus

Overview

Body lice, or Pediculus humanus humanus, are parasitic insects that live on the body and in the clothing or bedding of infested humans. Body lice frequently lay their eggs on or near the seams of clothing and must feed on blood and usually only move to the skin to feed. They exist worldwide and infest people of all races.

Pathophysiology

Pathogenesis

The life cycle of the body louse Pediculus humanus humanus, has three stages: egg, nymph, and adult.

1. Nits are body lice eggs. They are hard to see and are often confused for dandruff. Nits are laid by the adult female and are cemented at the base of the hair shaft nearest the skin . They are 0.8 mm by 0.3 mm, oval and usually yellow to white.
2. Nits take about 1 week to hatch (range 6 to 9 days). Viable eggs are usually located within 6 mm of the skin.
3. The egg hatches to release a nymph.
4. The nit shell then becomes a more visible dull yellow and remains attached to the hair shaft. The nymph looks like an adult body louse, but is about the size of a pinhead.
5. Nymphs mature after three molts and become adults about 7 days after hatching.
6. The adult louse is about the size of a sesame seed, has 6 legs (each with claws), and is tan to grayish-white . In persons with dark hair, the adult louse will appear darker. Females are usually larger than males and can lay up to 8 nits per day. Adult lice can live up to 30 days on a person’s body.
7. To live, adult lice need to feed on blood several times daily. Without blood meals, the louse will die within 1 to 2 days off the host.

Transmission

Body lice are spread through direct physical contact with a person who has body lice or through contact with articles such as clothing, beds, bed linens, or towels that have been in contact with an infested person. In the United States, actual infestation with body lice tends to occur only in persons, such as homeless, transient persons, who do not have access to regular (at least weekly) bathing and changes of clean clothes.

Epidemiology and Demographics

Body lice infestation is found worldwide but generally is limited to persons who live under conditions of crowding and poor hygiene who do not have access to regular bathing and changes of clean clothes, such as:

• the homeless
• refugees
• survivors of war or natural disasters

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.

References

1. http://www.cdc.gov/ncidod/dpd/parasites/lice/factsht_body_lice.htm
2. http://en.wikipedia.org/wiki/Body_louse

Acknowledgements

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