Complications

Secondary bacterial infection may be severe enough to make the child listless and feverish.

Differential diagnosis

All patients with recurrent impetigo or crusted eczema on their scalps should be carefully examined for the presence of nits.

Investigations

None are usually required.

Treatment

The finding of living moving lice means that the infestation is current and active, and needs treatment. Empty egg cases signify only that there has been an infestation in the past, but suggest the need for periodic re-inspection.

Dimeticone is a non-neurotoxic agent that coats the lice and probably suffocates them. It is rubbed into dry hair and scalp and left for 8 hours.This is then repeated 1 week later. Cure rates of 70% or more are reported and it is non-irritant and well tolerated.

Malathion and the synthetic pyrethroid permethrin have traditionally been used, but resistance to these neurotoxic pediculocides has been increasing since the 1990s. Sensitivity of less than 20% is reported in some areas, and resistance to more than one agent is also developing. Unsurprisingly, this has been accompanied by a big rise in infestation rates. Where resistance is not yet a problem these agents are more effective at killing adult lice and nymphs than eggs and should thus be applied on two occasions, 1 week apart. The second application is needed to kill young nymphs that hatch after the first application, usually 6–10 days after being laid. Lotions should remain on the scalp for at least 12 hours, and are more effective than shampoos.

Wet combing with a fine toothed comb every 3 days for 14 days is an alternative to the treatments mentioned above. The technique relies on physical removal of lice and eggs and is more effective than treatment with neurotoxic agents if carried out thoroughly. Shampoo or conditioner acts as a lubricant and helps with combing, but occasionally matting is so severe that the hair has to be clipped short. A systemic antibiotic may be needed to deal with severe secondary infection. Pillow cases, towels, hats and scarves should be laundered or dry cleaned. Other members of the family and school mates should be checked.

Systemic ivermectin therapy is reserved for infestations resisting the treatments listed above.

Cause

Body louse infestations are now uncommon except in the unhygienic and socially deprived. Epidemics also occur in times of social disruption, such as civil war or in refugee camps. Morphologically, the body louse looks just like the head louse, but lays its eggs in the seams of clothing in contact with the skin. Transmission is via infested bedding or clothing.

Presentation and course

Self-neglect is usually obvious; against this background there is severe and widespread itching, especially on the trunk. The bites themselves are soon obscured by excoriations and crusts of dried blood or serum. In chronic untreated cases (‘vagabond’s disease’), the skin becomes generally thickened, eczematized and pigmented; lymphadenopathy is common. Body lice can act as vectors for the organisms causing epidemic typhus, relapsing fever and trench fever.

Differential diagnosis

In scabies, characteristic burrows are seen (p. 253). Other causes of chronic itchy erythroderma include eczema and lymphomas, but these are ruled out by the finding of lice and nits.

Investigations

Clothing should be examined for the presence of eggs in the inner seams.

Treatment

First and foremost treat the infested clothing and bedding. Lice and their eggs can be killed by high temperature laundering, by dry cleaning and by tumble-drying. Less competent patients will need help here. Once this has been achieved, 5% permethrin cream rinse or 1% lindane lotion (United States only; Formulary 1, p. 405) may be used on the patient’s skin.