The head louse or Pediculus humanus capitis, is an insect and parasite whose only host are humans. Lice feed on blood several times daily and reside near the scalp to maintain its body temperature.
The head lice life cycle has three stages: egg, nymph, and adult.
Eggs: Nits are head lice eggs. They are quite small and have the appearance of a small sesame seed. Nits are laid by an impregnated female adult louse. Nits are glued onto the shaft of the hair usually close to the scalp but it is not uncommon to find nits in other areas of the hair. Nits are brownish in color when viable and whitish or yellowish in color when non-viable. Nits take around 5-7 days to hatch. Nits may be found for up to 2 months following an infestation
Nymphs: When a nit hatches a nymph is born. The nit shell or casing turns white or yellow and remains attached to the shaft of the hair. The nymph resembles an adult louse but is much smaller; about the size of a pin head. Nymphs mature after three molts and become adults about 7-10 days after hatching.
Adults: The adult louse is about the size of a grain of rice and has the appearance of an ant. Lice have 6 legs with claws or pinchers at the end of each. Lice are can be dark brown to whitish in color . Lice also have the ability to adjust their hue to better blend in with people who have darker or lighter hair. Male lice are smaller than female lice. Female lice can lay up to 8 eggs per day but usually 5 per day is the average. While on a persons head, adult lice can live for 30 days. Lice need to feed on blood multiple timer per day. Without food heat, the louse will die within 1 to 2 days.
Not every person infested with head lice experiences itching of the scalp. This is especially true when an infestation is in its early stages or a person does not have an allergic reaction to lice bites. It may take up to 3-6 weeks for the first signs of a lice infestation to begin.
Other symptoms may include:
•a tickling feeling or a sensation of something moving in the hair; •irritability and sleeplessness; and •sores on the head caused by scratching. These sores caused by scratching can sometimes become infected with bacteria normally found on a person’s skin.
Epidemiology & Risk Factors:
Head Lice infestation, in the United States is most prevalent in children ages 2-13 years of age as well as members of the same households and those in close contact. Head lice do not transmit any diseases but secondary bacterial infection of the skin resulting from scratching during a lice infestation can occur.
Getting head lice is not is not a result of poor hygiene or economic status. In fact lice prefer clean hair and scalp as it makes movement and feeding easier.
Head lice are spread primarily through direct contact with the head or hair of a person infested with lice. Children often contract lice while playing or interacting with other children at school, playgrounds, school plays and sleepovers.
Lice can less frequently be contracted from wearing an infested person’s: clothing, hats, hair ties or using an infested person’s combs or brushes. Also lying or sitting on furniture that had been used by an infested person can also result in contracting lice.
Experts estimate that 6 million to 12 million people become infested in the United States every year in children ages 3-11. Girls are more likely to contract lice than boys because of longer hair.
Closely examining the hair and scalp is necessary to determine a possible head lice infestation. Incorrect diagnosis of head lice is quite common among those unfamiliar with lice. To correctly diagnose head lice the best evidence will be the sighting of actual lice. Lice, in both adult and nymph stages, avoid light when possible and move very quickly. Therefore, it may be quite difficult to find them with a simple visual check of the scalp. The use of a fine toothed lice comb is recommended to facilitate the search of living lice. If living lice cannot be seen, finding lice eggs (nits) attached to the hair follicles may indicate the person is infested with lice. Often, nits are seen on hair near the back of the neck and hair behind the ears. Head lice and nits can be visible with the naked eye, however, use of reading glasses or a magnifying lens can be used to assist in finding moving lice or to identify viable nits and nit casings. Nits can often be confused with other particles found in hair such as dandruff, dirt and other miscellaneous debris. Nits found attached more than ¼ inch from the base of the hair shaft are quite often non-viable meaning they are hatched or dead.
Prevention & Control:
Head lice are primarily spread by direct head-to-head contact. Lice can also be spread by sharing brushes, clothing or belongings onto which lice have crawled. The odds of contracting lice from a louse that has fallen onto the floor or carpet are minuscule. Head lice can survive around 24-36 hours off of the human head as they to feed constantly on human blood to survive. Nits usually die within a week if they are not kept at the same temperature as that found with ¼ inch to the scalp.
Steps to Prevent Lice:
•Avoid head-to-head (hair-to-hair) contact. •Do not share clothing especially hats, scarves, jackets and hooded sweatshirts. •Do not share brushes, combs or towels. •Do not lie on beds, couches, pillows, carpets, or stuffed animals that have recently been in contact with an infested person. •Machine dry bed linens and clothing, and other items that an infested person used or wore during the previous 2 days, be sure to use the high heat setting during the drier cycle. Clothing and items that are not washable can be placed in a plastic bag for 3 days or dry-cleaned. •Vacuum the furniture where the infested person sat or lay. Place sheets over couches and fabric chairs for 3 days. •It is not necessary to use professional cleaning services or strong insecticides such as a bug bomb to prevent a re-infestation of lice.
It is important to explain to children the importance of following these tips to prevent head lice infestations.