Pediculosis I: What are lice?

Pediculosis is the infestation due to lice. There are three classes of lice: head lice (Pediculus humanus capitis), body lice (Pediculus humanus corporis) and pubic lice (Pthirus pubis; crab lice, to a better understanding).

Head lice are insects that feed human flood. Measures are 2 to 5 mm. Colour go from beige, white-grey to grey or dark brown. They are paler when emerge from the eggs and become darker when they have blood inside them. Lice have three pairs of legs in their abdomen. Every leg has a claw to grasps the hair. Average life is about one month. The female louse lays her eggs or nits near of the hair base. To do it, the female louse uses the last segment of her abdomen. This segment looks like and inverted V that grasps the hair in the egg laying. After a week the immature louse or nymph emerges from the nit. Nymphs feed blood and they need about 20 days to become adult (male or female).

Lice can parasite everybody and half of world population had been parasited in some moment in their lives. There isn’t relationship between prevalence of lice and hygiene practices; so to have lice isn’t cause of embarrassment.

Lice are more common in childhood (3 to 12 years old). 14-16% of the kids have lice at this moment. The girls (and women in general) are more parasited that men.

To be continued…

PS.- Problems with my English? I would appreciate your help.