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Pediculosis.

PEDICULOSIS СAPITIS — The head louse is an adaptable creature that has been able to survive in the advanced societies of the Western world. Children are affected most commonly; with the exception of the common cold, pediculosis capitis affects a greater number of elementary school students in North America than all other communicable diseases combined. It has been estimated that in 1997 approximately one of every four elementary level students in the United States was infested and up to one in every 10 children in school acquires head lice at some time. In one study, the estimated annual cost of head lice infestation in the USA was nearly $1 billion dollars.

Interaction with playmates, cross transfer from articles of clothing on adjacent hooks in school cloak rooms, and shared combs headphones, towels, and beds are important modes of disease spread. The incidence of head lice infestation varies only slightly inversely with socioeconomic level. Black children are affected much less frequently than whites and others, and males less than females; the reasons for these findings are not known. Hair length is not a factor.

Morphology and habits of capitis — The head louse is a gray-white, active insect 3 or 4 mm in length. The female is a little longer than the male. Both sexes are equipped with mouth parts adapted to sucking blood and legs adapted to grasping hairs. The life span of the female is about one month, during which time she lays 7 to 10 eggs each day, cementing them firmly to the ease of a host hair. The eggs, commonly called "nits," are oval lidded capsules that hatch in eight days releasing nymphs that require another eight days to mature. After hatching, egg cases become white and more visible. Adults feed voraciously both on the scalp and adjacent areas of the face and neck.

Nits remain firmly attached to the hair shaft and move away from the scalp as the hair grows. The signs and symptoms are

• a tickling feeling of something moving in the hair;

• itching caused by an allergic reaction to the bites;

• sores on the head caused by scratching;

• these sores on the head can sometimes become infected;

• irritability

Medicated shampoos or cream rinses are preferred for treating people with head lice. Retreatment after seven to 10 days is recommended to assure that no eggs have survived. Nit combs are available to help remove nits from hair.

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