Pediculosis

Contact Precautions

Any human infestation of lice is known as pediculosis. Pediculosis can occur anywhere on the body. In the most common type, pediculosis capitis, lice feed on the scalp and, rarely, on the skin under the eyebrows, eyelashes, and beard. In pediculosis corporis, lice live next to the skin in clothing seams. In pediculosis pubis, lice are found primarily in pubic hairs but may extend to the eyebrows, eyelashes, and axillary or body hair. All types of lice feed on human blood and lay eggs (nits) on body hairs or clothing fibers. After the nits hatch, the lice must feed within 24 hours or they die; lice mature within 2 to 3 weeks after hatching. When a louse bites, it injects a toxin into the skin that produces mild irritation and a purpuric spot.

Causes

Pediculosis capitis (head lice) is caused by Pediculus humanus capitis, while Pediculus humanus corporis causes pediculosis corporis (body lice). Phthirus pubis causes pediculosis pubis (crab lice).

Pediculosis capitis commonly affects children, spreading through shared clothing and personal articles or by being in close proximity (playrooms or institutions). Pediculosis corporis is associated with close, crowded living situations (crowded buses and trains) and prolonged wearing of the same clothing; it spreads through shared clothing and bedsheets. Pediculosis pubis is associated with crowded living conditions and is transmitted through sexual intercourse or by contact with clothing, bedsheets, or towels harboring lice.

Complications

Excoriation and secondary bacterial infections from scratching are common complications of pediculosis. Left untreated, pediculosis may result in dry, hyperpigmented, thickly encrusted, scaly skin with residual scarring. Lice may carry Staphylococcus aureus and group A Streptococcus pyogenes on their surface and transmit pathogens to others. P. humanus corporis is a known vector of three major bacterial diseases (relapsing fever, typhus, and trench fever), all of which have caused epidemics.

Assessment Findings

In a patient with pediculosis capitis, inspection notes excoriation (with severe itching), pruritic papules or wheals from bite marks, hair that is matted and may have exudates under the matting (in severe cases), and posterior auricular and cervical lymphadenopathy. Hair shafts display oval, gray-white nits that can’t be removed easily. A patient with pediculosis corporis may have excoriated red papules on the axilla, groin, and trunk and small, gray-blue spots (maculae ceruleae) on the thighs or upper body. Nits are found on clothing, especially in the seams. Inspection of a patient with pediculosis pubis reveals skin irritation from scratching, maculae ceruleae, and inguinal and axillary lymphadenopathy. The nits are attached to pubic hairs.

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