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Since the 1970s, there has been a global increase in the number of cases of head lice or pediculosis capitis. This plague is considered by some authors as the most common contagious disease in schools, after respiratory infections. In fact, it mainly affects children, and in particular those between the ages of 5 and 11. Lice are present all year round, with peaks in summer and fall.
Lice are small parasites that feed on human blood and, for this reason, are called hematophages. They tolerate the lack of food very badly and live by feeding almost continuously. This is the reason why they always live on top of their host and if they separate, they end up dying in a short time. They inhabit the head of children and adults, and prefer the hair and scalp that is found in the areas of the neck and behind the ears.
During their life cycle, lice can be seen in three different ways: the nit, the nymph, and the adult louse.
The nit: it is the egg that is often mistaken for dandruff flakes or traces of hair spray. Nits are attached to hair, are white or yellowish in color, and are oval in shape. Their size is approximately 1 mm in length and they are globose in shape. The eggs take a week to hatch. Nits adhere strongly to the base of the hair with an adherent discharge, which is the saliva of the louse. It acts as a very powerful glue, insoluble in water and very resistant.
Nymphs: it is the young lice. They look the same as adult lice, but are smaller in size. They become adult subjects within 7 days and feed on the blood of their host.
The adult louse: It is similar in size to sesame seed, has 3 pairs of legs and is gray-white in color. The females are usually somewhat larger than the males. Adult lice usually live for about 30 days on the host's head, feeding on their blood, and if they fall off the head they die in about 2 days.
The life cycle of the louse has 3 stages: nit, nymph and adult louse. The nits or eggs that females lay near the base of the hair are usually located less than 6 mm from the scalp. These eggs hatch after a week, giving rise to the nymphs, with a grayish-yellow color, which after 7 days acquire adult size. The females are usually larger in size and lay 8 eggs a day. Fertilized females typically lay 250 to 300 eggs during their life cycle.
1. The life cycle of the louse lasts from 30 to 40 days. The adult stage is reached after approximately 10 days and during that time 3 successive molts occur. Thus, from the laying of the egg to the emergence of the adult, a total of 17 days elapse, at which point copulation and reproduction begin.
2. Between days 17 to 19, lice eat and copulate almost exclusively. On these same days, the female lays her first egg, because for this she only needs or takes one day after copulation.
3. On days 19 and 35 of life, the male will copulate with any female that passes by him and, at the same time, the females will not stop laying eggs, 4 to 8 a day, which can be a total of 300 eggs.
Therefore, day 17 is a reference number in the fight against lice and the success of the treatment cannot be assured until 17 days have elapsed. This also means that we must insist on treatment during these 17 days until we can be sure that there will be no egg or fertile female capable of making head lice reappear.
Marisol New. Editor of our site
If you want to know more about lice, we have prepared a series of lice and pediculosis videos with an expert who will give you a lot of information about what they are, how to prevent them and how to treat them.
You can read more articles similar to Lice: the life cycle of lice in children, in the category of Lice and nits on site.