Lice are ectoparasites that feed on
human blood after piercing the skin
and injecting their saliva.
The 3 types of lice infestations are
pediculosis capitis (head lice),
pediculosis corporis (body lice),
and pediculosis pubis (pubic lice,
ie, crabs).
The head louse, the most common of
the 3 species, is spread by close
physical contact and by shared
fomites (eg, combs, brushes, hats,
scarves, bedding).
human blood after piercing the skin
and injecting their saliva.
The 3 types of lice infestations are
pediculosis capitis (head lice),
pediculosis corporis (body lice),
and pediculosis pubis (pubic lice,
ie, crabs).
The head louse, the most common of
the 3 species, is spread by close
physical contact and by shared
fomites (eg, combs, brushes, hats,
scarves, bedding).
Skin Care
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Lice
| Life Cycle The adult head louse can live 5-6 weeks on the scalp, but it survives only 1-2 days away from its host. Most infestations involve 10-20 adults. days. Cooler temperatures retard both hatching and days. Cooler temperatures retard both hatching and maturationmaturation |
| Prevalence US schools. Hair length and personal cleanliness are US schools. Hair length and personal cleanliness are not factors in infestation rates. not factors in infestation rates. |
| Prevalence Race: All races are affected. Reported incidence in African Americans in the United States is relatively less than in whites. Sex: Prevalence is higher in females than in males. Age: All age groups are affected. |
| Physical: Pruritus may lead to secondary excoriations that produce skin infection and regional lymph node enlargement. However, such findings are nonspecific. Pediculosis capitis Although head lice are found on any part of the scalp, they most commonly are found in the postauricular and occipital areas. Eggs depend upon body warmth to incubate. Nits are attached to hair shafts within 3-4 mm of the scalp by a sticky substance. Since hair grows approximately 10 mm/mo, the distance of nits from the scalp can be used to estimate the duration of infestation. |
| Lab Studies: The identification of adult lice or nits is diagnostic. The presence of bruiselike bites or dark specks of louse dung suggest the diagnosis of louse infestation. Lice move rapidly. A helpful technique is to fasten a piece of transparent adhesive tape to the infested areas. Lice stick to the tape. The tape then becomes a convenient coverslip for a microscopic slide. Mature lice are approximately the size of a sesame seed (3-4 mm) with an elongated body, 3 pairs of legs, and narrow anterior mouthparts. Wide crablike bodies and claws distinguish pubic lice. Nits are approximately 1 mm in length, transparent, and flasklike in appearance. Nits and lice fluoresce with a Wood light. Properly evaluating persons who have been raped is essential. Evidence should be collected in such a way as to avoid contamination and to ensure a legal chain of custody. Human DNA can now be identified in the amount of blood present in a pubic louse. Lice recovered after an attack have the potential to provide evidence valuable in securing a conviction. |
| Patient Education: In cases of school-wide infestations, the social stigma associated with infestation must be addressed. The community must address the problem honestly and openly, or the infestation will continue. Louse infestation is a community-wide problem. Patients must realize that pediculicides are ineffective against young nits that lack a nervous system. |
