The head louse (Pediculus humanus capitis) is an obligate ectoparasite of humans. Scientifically they are classified as insects or Insecta. They are wingless parasites that spend their entire life on the human scalp sucking on human blood, from which they derive their nutrition. Humans are the only specie known host this parasite. Head lice cannot fly, and their short low down legs make them incapable of jumping, or even walking efficiently on flat surfaces. The size of the adult head lice varies from 1-3 mm in length.
In order to diagnose the infestation, the entire scalp should be combed thoroughly with a louse comb and the teeth of the comb should be examined for the presence of living lice each time after the comb passes through the hair. The use of a louse comb is the most effective way to detect living lice.
In cases of children with long and curly/frizzy hair, an alternative method of diagnosis is examination by parting the hair at 2 cm intervals to look for moving lice near the scalp. With both methods, special attention should be paid to the area near the ears and the nape of the neck. The examiner should examine the scalp for at least 5 min. The use of a magnifying glass to examine the material collected between the teeth of the comb could prevent misdiagnosis.
Lice infestation is most commonly found in children and it is highly contagious. Head lice can spread like a wildfire once it has started, and can create more of psychological problems than medical problems for the child. Many a times, we see children who are outcast from peer groups because of this infestation. Moreover, it also has several medical repercussions such as Pruritus (itching). Bites of head lice can be seen, especially in the neck of long-haired individuals when the hair is pushed aside. In rare cases, the itch scratch cycle can lead to secondary infection with impetigo and pyoderma. Swelling of the local lymph nodes and fever are rare. Head lice are not known to transmit any pathogenic microorganisms.
The head lice are normally brown or black in colour, but they do appear red after immediate consumption of human blood. The body of the head lice is dorso-ventrally flattened and comprises of the head, thorax and abdomen. The head contains one pair of antenna, each with five segments, protruding from the insect's head. Head lice also have one pair of eyes. Eyes are present in all species within Pediculidae (the family of which the head louse is a member), but are reduced or absent in most other members of the Anoplura suborder.
Six legs project from the compound segments of the thorax. As is typical in Anoplura, these legs are short and terminate with a single claw and opposing "thumb".
Head lice are oviparous and they lay their eggs on the hair of human beings. These louse eggs contain a single embryo. The eggs are normally laid at the base of the host hair shaft. Like most insects, head lice are oviparous. Louse eggs contain a single embryo, and are attached near the base of a host hair shaft. Eggs are generally laid within 1 cm of the scalp surface.
Some ways in which one can prevent and combat head lice:
Lice on the hair and body are usually treated with medicated shampoos or cream rinses. Nit combs can be used to remove lice and nits from the hair. Some lice have become resistant to certain (but not all) insecticides used in commercially available anti-louse products. A physician or pharmacist can prescribe or suggest treatments. Because empty eggs of head lice may remain glued on the hair long after the lice have been eliminated, treatment should be considered only when live (crawling) lice are discovered.
Examination of the child’s head at regular intervals using a louse comb allows the diagnosis of louse infestation at an early stage. Early diagnosis makes treatment easier and reduces the possibility of infesting others. In times and areas when louse infestations are common, weekly examinations of children, especially those 4–13 yrs old, carried out by their parents will aid control. Additional examinations are necessary, if the child came in contact with infested individuals, if the child frequently scratches his/her head, or if nits suddenly appear on the child’s hair. Keeping long hair tidy could be helpful in the prevention of infestations with head lice. In order to prevent new infestations, the hair of the child could be treated with 2–4 drops of concentrated rosemary oil every day, before he/she leaves for school or kindergarten. The oils can be combed through the hair using a regular comb or brush. Hygiene also plays a very important role for prevention of hair lice.