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There is 2 million of pediculosis by year in the US. About 6–12 million people, mainly children, are treated annually for head lice in the United States alone. Girls are two to four times more frequently infested than boys. Children between 4 and 13 years of age are the most frequently infested group. What is Pediculosis? Pediculosis is an infestation of lice. Head lice are wingless insects spending their entire life on human scalp and feeding exclusively on human blood.. The term "nit" refers to either a louse egg or a louse nymph. What does head lice look like? Cick on head lice pictures to zoom.
Lice Eggs: Lice Egg laying behavior is temperature dependent. In cool climates, eggs are generally laid within 1 cm of the scalp surface. In warm climates, and especially the tropics, eggs may be laid 6 inches (15 cm) or more down the hair shaft. To attach each egg, the adult female secretes a glue from her reproductive organ. This glue quickly hardens into a "nit sheath" that covers the hair shaft and the entire egg except for the operculum – a cap through which the embryo breathes. The glue is made of proteins similar to hair keratin. Each egg is oval-shaped and about 0.8 mm in length. They are tan- to coffee-colored so long as they contain an embryo, but appear white after hatching. Typically, a hatching time of six to nine days. After hatching, the louse nymph leaves behind its eggshell, still attached to the hair shaft. The empty eggshell remains in place until physically removed by abrasion or the host, or until it slowly disintegrates, which may take months or years. How do head lice feed? Lice are blood-feeders and they bite the skin four to five times daily to feed. To feed, the louse bites through the skin and injects saliva, which prevents blood from clotting; it then sucks blood into its digestive tract. Bloodsucking may continue for a long period if the louse is not disturbed. While feeding, lice may excrete dark red feces onto the skin. Position on host: Although any part of the scalp may be colonized, lice favor the nape of the neck and the area behind the ears, where the eggs are usually laid. How does head lice migrate? Lice have no wings and no powerful legs for jumping, so they move by using their claw-like legs to transfer from hair to hair. Head-to-head contact is by far the most common route of lice transmission. |
