eMedicine Specialties > Pediatrics: General Medicine > Dermatology
Pediculosis (Lice)
Updated: May 4, 2009
Introduction
Background
Ye ugle, creepin, blastit wonner,
Detested, shunned by saunt an' sinner,
How daur ye set your fit upon her,
Sae fine a lady.
Gae somewhere else and seek your dinner,
On some poor body.-- Robert Burns (Scotland, 1759-96), written after seeing a louse move across a lady's bonnet during the church sermon
Pathophysiology
Lice are ectoparasites who live off of human hosts. Lice feed on human blood after piercing the skin and injecting saliva. The injected saliva often causes pruritus. Lice can survive away from a human host for short periods of time. However, lice die of starvation within 10 days of removal from their human host. A mature female lays 3-6 eggs, also called nits, per day. Nits are white and less than 1 mm long. Nits hatch in 8-10 days, reach maturity in 12-15 days, and live as adults for about 10 days.
Different species of lice prefer to feed on certain locations on the body of the host. Types of lice include Pediculosis capitis (head lice), Pediculosis corporis (body lice), and Pediculosis pubis (pubic lice, sometimes called crabs).
The head louse, Pediculus humanus capitis, has an elongated body and narrow anterior mouthparts. Body lice look similar but lay their eggs (nits) on clothing fibers instead of hair fibers.
The pubic louse, Pthirus pubis, is identified by its wide crablike body.
Mortality/Morbidity
Body lice can be vectors for disease such as epidemic typhus and relapsing fever. Violation of the integrity of the skin from a bite can lead to bacterial infection, including methicillin-resistant Staphylococcus aureus (MRSA). More commonly, infestation with lice produces social embarrassment and isolation rather than medical disease.
Race
People of all races are affected. Reported incidence in African Americans is relatively less than in other American races.
Sex
Males and females are equally at risk for infestation.
Age
People of all age groups are affected. Head lice infestation is common among young school children in the United States. One study estimates that 12-24 million days of school are lost because of "no-nit" school policies.1
Clinical
History
- Patients may present after discovering lice or nits indicative of infestation.
- Children may be brought to their pediatrician when concerned parents learn about a case of lice at the child's school or daycare center.
- Pruritus is the most common symptom of infestation.
- Affected children are often asymptomatic.
Physical
Pruritus may lead to secondary excoriations that predispose to secondary skin infection and regional lymph node enlargement. However, these are nonspecific findings.
- Pediculosis capitis
- Although head lice are found on any part of the scalp, they are most commonly found in the postauricular and occipital areas.
- Eggs depend on body warmth to incubate; a sticky substance attaches nits to the hair shafts within 3-4 mm of the scalp. Because hair grows approximately 10 mm per month, the distance of nits from the scalp can be used to estimate the duration of infestation.
- Wet combing is an accurate method to diagnose active lice infestation.2
- Pediculosis corporis
- Bites from body lice can be found in any area of the body.
- Because nits are laid in the host's clothing (especially along inner seams of clothing), nits are not found on the hair as with head lice and pubic lice.
- Pediculosis pubis: Pubic lice can be found in hairy areas throughout the body, but they prefer the perineum and pubic areas. Occasionally, the infestation may be present in the eyebrows and eyelashes.
Causes
- Pediculosis is usually caused by direct contact with an infested person.
- Fomites such as clothing, headgear, combs, and hairbrushes may play a role in the spread of head lice.
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References
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Clore ER, Longyear LA. A comparative study of seven pediculicides and their packaged nit removal combs. J Pediatr Health Care. Mar-Apr 1993;7(2):55-60. [Medline].
Gilbert DN, Moellering RC Jr, Samde MA. The Sanford Guide to Antibiotic Therapy 1998. Hyde Park, Vt: Antibiotic Therapy; 1998:94-5.
Halpern JS. Recognition and treatment of pediculosis (head lice) in the emergency department. J Emerg Nurs. 1994;20:130-133. [Medline].
Hart G. Risk profiles and epidemiologic interrelationships of sexually transmitted diseases. Sex Transm Dis. May-Jun 1993;20(3):126-36. [Medline].
Heukelbach J, Feldmeier H. Ectoparasites--the underestimated realm. Lancet. Mar 13 2004;363(9412):889-91. [Medline].
Huynh TH, Norman RA. Scabies and pediculosis. Dermatol Clin. Jan 2004;22(1):7-11. [Medline].
Ibarra J, Hall DM. Head lice in schoolchildren. Arch Dis Child. Dec 1996;75(6):471-3. [Medline].
Klaus S, Shvil Y, Mumcuoglu KY. Generalized infestation of a 3 1/2-year-old girl with the pubic louse. Pediatr Dermatol. Mar 1994;11(1):26-8. [Medline].
Further Reading
Keywords
pediculosis, lice, louse, nits, nymphs, pediculosis capitis, head lice, Pediculosis corporis, body lice, Pediculosis pubis, pubic lice, crabs, typhus, sexually transmitted diseases, STDs, child sexual abuse, Anoplura, sucking lice, biting lice, Mallophaga, pruritus, treatment, diagnosis, itching, scratching
