Types of lice include pediculosis capitis (head lice), pediculosis corporis (body lice) and pediculosis pubis (pubic lice, sometimes called crabs).

Mortality/Morbidity: Body lice can be vectors for disease such as epidemic typhus and relapsing fever. More often, infestation with lice produces social embarrassment and isolation, rather than medical disease.

Race: 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.

History:

• Patients may present after discovering lice or nits, which indicate infestation.

• Children may be brought to their pediatrician when concerned parents learn about a case of lice at their child's school or day care center.

• Pruritus is the most common symptom of infestation.

• Affected children may be 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 most commonly are found in the post-auricular and occipital areas.

• Eggs depend upon body warmth to incubate, so a sticky substance attaches nits to the hair shafts within 3-4 mm of the scalp. Since hair grows approximately 10 mm per month, the distance of nits from the scalp can be used to estimate the duration of infestation.

• Pediculosis corporis

• Bites from body lice can be found in any area of the body.

• Since 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 prefer the perineum and pubic areas. Occasionally, the infestation may be present in the eyebrows and eyelashes.

Causes:

• Pediculosis is usually caused by contact with an infested person.

• Fomites such as clothing, headgear, combs and hairbrushes may play a role in the spread of head lice.

Lab Studies:

• The diagnosis rests on the observation of nits, nymphs or mature lice.

• Observing lice is difficult. Nymphs and mature lice, despite being unable to hop or jump, can move rapidly through dry hair.

• Mature lice are 3-4 mm long, approximately the size of a sesame seed. Nits are much smaller, about 1 mm. The pubic louse is about the same length, but has a wider body than the head or body louse.

• The use of a magnifying glass and the knowledge of where to look aid the diagnosis.

• Nits are fluorescent under a Wood's light.

Medical Care:

• Patient therapy consists of 2 parts: medications and environmental control measures.

• Medical treatment should include contacts of infested patients, especially sexual partners.

• Medications are less essential than environmental measures in the treatment of body lice. Many infectious disease authorities recommend only environmental measures to treat body lice. Patients with body lice should have infested clothing removed and treated. If medical therapy is prescribed as an adjunct to environmental measures, one of the therapies below may be selected.

Drug Category: Anthelmintics -- Parasite biochemical pathways are different from the human host, thus toxicity is directed to the parasite, egg, or larvae. Mechanism of action varies within the drug class. Antiparasitic actions may include the following:

1. Inhibition of microtubules causes irreversible block of glucose uptake
2. Tubulin polymerization inhibition
3. Depolarizing neuromuscular blockade
4. Cholinesterase inhibition
5. Increased cell membrane permeability, resulting in intracellular calcium loss
6. Vacuolization of the schistosome tegument
7. Increased cell membrane permeability to chloride ions via chloride channels alteration

Further Outpatient Care:
 

• Treatment of the patient's environment (control measures)

• Potential fomites such as towels, pillow cases, sheets, hats and children's stuffed animals may benefit from laundering in hot water and machine drying, using the hottest cycle. Temperature exceeding 131°F (55°C) for more than 5 minutes will kill eggs, nymphs and mature lice.

• Combs and brushes can be treated by soaking for at least 5 minutes in very hot water (greater than 131°F or 55°C).

• Dry cleaning may be an effective alternative.

• Since adult lice cannot survive for long if separated from a host, and since eggs hatch in 6-10 days, carefully sealing potential fomites in plastic bags for 12-14 days can be effective. This technique works well for objects such as stuffed animals that do not tolerate laundering or dry cleaning.

• Vacuuming selected areas of the home, like couches used by infested patients, is recommended by some as an adjunctive control measure.

• Chemical insecticide sprays used in the home environment have not been shown to be effective in the control of head lice.

Deterrence/Prevention:

• To prevent reinfestation, contacts of an infested patient should be treated and retreated at the same time as the patient.

Prognosis:

• Treatments are highly effective in killing nymphs and mature lice, but less effective in killing eggs. After proper initial treatment, children may return to school providing that repeat therapy is administered in 7-10 days.

Patient Education:

• Patients should be provided with detailed instructions regarding the application of medications used in treatment.

• Most patients will benefit from an understanding of the life cycle of lice, and the limitations of medical therapy (ie, medications are incompletely ovicidal). Compliance with a second treatment in 7-10 days may be enhanced if patients understand the need for the second treatment to kill newly hatched nymphs.